Tag Archives: Food

Faking Lateral Flow Tests: the problem with pH

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Fruit juices can be used to generate a fake positive on COVID-19 LFTs

On Thursday last week, I got a message from Prof Mark Lorch — my sometime collaborator on supercharacter-based ramblings.

“Have you seen the reports of kids fooling the Covid lateral flow tests and getting false +ve results by adding orange juice to the devices?” he wondered.

At this point, I had not – but I quickly got up to speed. Mark had previously made an excellent video explaining how lateral flow test (LFT) devices work, so it was just a case of working out, firstly, whether the false positives were reproducible, and secondly, speculating what, exactly, was causing them.

Thus ensued some interesting discussion which ultimately led to a couple of articles from Mark. One at The Conversation and another, slightly more recently, at BBC Future.

I won’t delve into LFT-related science, because Mark has covered it (really, check the video and those articles), but I am going to talk a little bit about pH – the scale chemists use to measure how acidic or alkaline solutions are – because as soon as news of this started to gain traction people, predictably, started trying it out themselves. And that was when things got really interesting.

Image

The buffer included with LFTs is effective at neutralising the pH of solutions, for example, cola

Now, firstly, and importantly: the test kits come with a small vial of buffer solution. Buffers are substances which resist pH changes. As I’ve written before, our bodies naturally contain buffer systems, because keeping the pH of our blood and other body fluids constant is important. In fact, if blood pH varies even a little, you’re in all sorts of serious trouble (which is how we can be certain that so-called “alkaline” diets are a load of hooey). Anyway, the important message is: don’t mix any liquid you’re testing with the contents of that phial, because that will neutralise it.

If you want to try this for yourself, just drop the liquid you want to test directly into the window marked S on the test.

That out of the way, let’s get back to pH. It’s a scale, usually presented as going from 0–14, often associated with particular colours. The 0 end is usually red, the 7 in the middle is usually green, while the 14 end is usually dark blue.

These colours are so pervasive, in fact, that I’ve met more than one person with the idea that acids are red, and alkalis are blue. This isn’t the case, of course. The red/green/blue idea largely comes from universal indicator (UI), which is a mixture of dyes that change colour at different pH values. There’s also a common indicator called litmus (people sometimes mix up UI and litmus, but they’re not the same) which is also red in acid and blue in alkali.

Some species of hydrangea produce pink flowers in alkaline soil, blue in acid soil.

There are actually lots of pH indicators, with a wide variety of colour changes. Phenolphthalein, for example, is bright pink in alkali, and colourless in acids. Bromocresol purple (they have such easy-to-spell names) is yellow in acids, and violet-purple in alkalis.

Many plants contain natural indicators. Just to really mix things up, some species of hydrangea produce flowers that are blue-purple when they’re grown in acidic soil, and pink-red in alkaline conditions.

Bottom line? Despite the ubiquitous diagrams, pH has nothing to do with colour. What it is to do with is concentration. Specifically, the concentration of hydrogen ions (H+) in the solution. The more H+ ions there are, the more acidic the solution is, and the lower the pH. The fewer there are, the less acidic (and the more alkaline, and higher pH) it is.

In fact, pH is a log scale. When the concentration changes by a factor of 10, the pH changes by one point on the scale.

This means that if you take an acid with pH of 2, and you dilute it 1 part to 10, its pH changes to 3 (i.e. gets one point more alkaline, closer to neutral). Likewise, if you dilute an alkali with a pH of 10 by 1:10, its pH will shift to 9 (again, closer to neutral).

And what this means is that the pH of substances is not a fixed property.

Louder for anyone not paying attention at the back: the pH of substances is not a fixed property!

Yes, we’ve all seen diagrams that show, for example, the pH of lemon juice as 2. This is broadly true for most lemons, give or take, but if you dilute the lemon juice, the pH rises.

Apple juice dropped directly into the test window gives an immediate “positive” result.

I am by no means an expert in commercial, bottled lemon juice, but I reckon a lot of them have water added – which may well explain why @chrismiller_uk was able to get a positive result, while @BrexitClock, using a French bottle of lemon juice, couldn’t.

Mark and I concluded that the pH you need to aim for is probably around 3–4. Go too low, and you don’t get a positive (and you might wipe out the control line, too). Likewise, too high also won’t work.

Myself, I tried apple juice. I couldn’t find the indicator colour key for my indicator paper (I really must clear out the drawers one of these days) but it’s broadly the same as Mark’s cola photo, up above. In other words, the apple juice is about pH 3. And it gives a beautiful positive result, immediately.

One more interesting observation: Mark recorded some time-lapse video comparing orange juice to (sugar-free) cola. It shows the cola test line developing a lot more slowly. We’re not entirely sure why, but it may be pH again: orange juice almost certainly has a lower pH than cola.

For any parents reading this thinking we’re being terribly irresponsible, fear not: as Prof Lorch has made clear in his articles, you can identify a fake by waiting a few minutes and then dropping some of the buffer solution provided in the test window. As I said above, this will neutralise the pH, and the positive test line will disappear. Extra buffer won’t change a genuinely-positive test, because the antibodies bind very tightly (more technical info here). To quote Mark: “you’d need a swimming pool’s worth of buffer to have any chance of washing [the antibodies] off.”

Alternatively, you can just watch your teenager as they do their tests, and make sure they’re not getting up to anything nefarious…

Have you tried to trick an LFT? If you have, share your results! Look us up on Twitter: @chronicleflask and @Mark_Lorch or add a comment below. We’d love to see your photos!

Do you want something non-sciency to distract you from, well, everything? Why not take a look at my fiction blog: the fiction phial? You can also find me doing various flavours of editor-type-stuff at the horror podcast, PseudoPod.org – so head over there, too!

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. Content is © Kat Day 2021. You may share or link to anything here, but you must reference this site if you do. You can support my writing my buying a super-handy Pocket Chemist from Genius Lab Gear using the code FLASK15 at checkout (you’ll get a discount, too!) or by buying me a coffee – the button is right here…
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Onerous ovens: why is cleaning the cooker such a chore?

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As I write Thanksgiving was a few days ago, when most Americans traditionally cook a very large meal based around roasted turkey. Most Brits – and other countries of course – have the same thing coming up soon in the form of Christmas, and there are lots of other celebrations around this time of year that seem to feature cooking and food quite heavily.

Whatever your traditions, then, it’s a time when many of us frown critically at the dark, sticky depths of our oven and wonder if, perhaps, we should attempt to give it a clean. Or at least pay someone else to come and clean it.

Why is oven cleaning such a difficult and unpleasant job, anyway? It’s not that hard to clean other surfaces, is it? Why are ovens so particularly awful?

Well, to explain this, we first need to understand fats.

Fats vaporise during cooking.

Most of the grime in your oven is fat, combined with the carbonised remains of… something or other. The sorts of fats that are common in animal and plant products have boiling points around the 300 oC mark (animal fats typically having higher values than plant oils), but they start to form vapours at much lower temperatures, and certainly at typical cooking temperatures there’s plenty vaporised oil around. Besides, under typical conditions most oils will “smoke” – i.e. start to burn – long before they get close to boiling.

We’re all familiar with the idea that fats don’t mix well with water, and herein lies the problem: all that fatty gloop that’s stuck to the inside of your oven just doesn’t want to come off with standard cleaning methods, particularly when it’s built up over time.

Can chemistry help us here? What are fats, chemically? Well, they’re esters. Which may or may not mean anything to you, depending on how much chemistry you can remember from school. But even if you don’t remember the name, trust me, you know the smell. In particular, nail polishes and nail polish removers contain the simple ester known as ethyl acetate, otherwise known as ethyl ethanoate. (Some people say this chemical smells like pear drops which… only really helps if you know what pear drops smell like. Look, it smells of nail polish, okay?)

Fats are esters (image source)

Anyway, the point is that esters have a particular sequence of atoms that has a carbon bonded to an oxygen, which is bonded to another carbon, which is in turn double-bonded to oxygen. This is a bit of a mouthful, so chemists often write it as COOC. In the diagram here, oxygen atoms are red while carbon atoms are black.

There are actually three ester groups in fat molecules – which explains why fats are also known as triglycerides.

In terms of general chemistry, esters form when a carboxylic acid (a molecule which contains a COOH group) reacts with an alcohol (a molecule that contains an OH group). And this is where it all starts to come together – honest – because you’ve probably heard of fatty acids, right? If nothing else, the words turn up in certain food additive names, in particular E471 mono- and diglycerides of fatty acids, which is really common in lots of foods, from ice cream to bread rolls.

Glycerol is a polyol — a molecule that contains several alcohol groups (image source)

Well, this reaction is reversible, and as a result fats (which are esters, remember) break up into fatty acids and glycerol – which is a polyol, that is, a molecule with several alcohol groups. Or, to look at it the other way around: fats are made by combining fatty acids with glycerol.

And the reason it’s useful to understand all this is that the way you break up esters, and therefore fat, is with alkalis. (Well, you can do it with acid, too, but let’s not worry about that for now.)

Strong alkalis break up fats in a chemical reaction called hydrolysis — the word comes from the Greek for water (hydro) and unbind (lysis) and so literally means “split up with water”. Humans have known about this particular bit of chemistry for a long time, because it’s fundamental to making soap. As I said a few months ago when I was banging on about hand-washing, the ancient Babylonians were making soap some 4800 years ago, by boiling fats with ashes – which works because alkaline compounds of calcium and potassium form when wood is burnt at high temperatures.

The grime in ovens is mostly fat.

The really clever thing about all this is that two things are happening when we mix alkali with fat: not only are we breaking up the fat molecules, but also the substances they break up into are water-soluble (whereas fats, as I said at the start, aren’t). Which makes them much easier to clean away with water. Obviously this is the very point of soap, but it’s also handy when trying to get all that baked-on gunk off your oven walls.

Now, in theory, this means you could get some lye (aka sodium hydroxide, probably), smear it all over your oven and voilà. But I don’t recommend it, for a few reasons. Firstly, it’s going to be difficult to apply, since sodium hydroxide is mostly sold as pellets or flakes (it’s pretty easy to buy, because people use it to make soap).

Sodium hydroxide, sometimes called lye, is often sold in the form of pellets.

But, you say, couldn’t I just dissolve it in water and spray or spread it on? Yes, yes you could. But it gets really, really hot when you mix it with water. So you need to be incredibly careful. Because, and this is my next point, chemically your skin is basically fat and protein, and this reaction we’re trying to do on oven sludge works equally well on your skin. Only, you know, more painfully, and with scarring and stuff. In short, if you’re handing lye, wear good nitrile on vinyl gloves and eye protection.

Actually, regardless of how you’re cleaning your oven you should wear gloves and eye protection, because the chemicals are still designed to break down fats and so… all of the above applies. It’s just that specially-designed oven cleaners tend to come with easier (and safer) ways to apply them. For example, they might come as a gel which you can paint on, and/or with bags that you can put the racks into, and may also be sold with gloves and arm protectors (but rarely goggles – get some separately). They might also have an extra surfactant, such as sodium laureth sulfate, added to help with breaking down grease. The main ingredient is still either potassium hydroxide or sodium hydroxide, though.

Well, possibly, but also not really, if you’re sensible.

As an aside, it makes me smile when I come across an article like this which talks about the “serious” chemicals in oven cleaners and more “natural” ways to clean your oven. The “natural” ways are invariably weak acids or alkalis such as lemon juice or baking soda, respectively. They’re essentially ineffective ways of trying to do exactly the same chemistry.

And okay, sure, the gel and the bag and so on in the modern kits are newer tech, but the strong alkali? Nothing more natural than that. As I said at the start, humans have literally been using it for thousands of years.

A point which really cannot be repeated enough: natural does not mean safe.

Fumes can be irritating to skin, eyes and lungs.

Speaking of which, you will get fumes during oven cleaning. Depending on the exact cleaning mixture involved, these will probably be an alkaline vapour, basically (haha) forming as everything gets hot. Such vapour is potentially irritating to skin, eyes and lungs, but not actually deadly toxic. Not that I recommend you stick your head in your freshly-scrubbed oven and inhale deeply, but you take my point. It might give food a soapy, possibly bitter (contrary to what’s stated in some text books, not all alkalis taste bitter, but do not experiment with this) taste if you really over-do it.

In short, if you’re cleaning your oven yourself: follow the manufacturer’s instructions, make sure your kitchen is well-ventilated, leave the oven door open for a while after you’ve finished and, to be really sure, give all the surfaces an extra wash down with plenty of water.

Put the cleaning off until January – after all, the oven’s only going to get dirty again.

And that’s… it, really. Whether you’re cleaning your own oven or getting someone else to do it for you, the chemistry involved is really, really old. And yes, the chemicals involved are hazardous, but not because they’re not “natural”. Quite the opposite.

Or you could just leave it. I mean, it’s only going to get dirty again when you cook Christmas dinner, right?

If you’re studying chemistry, have you got your Pocket Chemist yet? Why not grab one? It’s a hugely useful tool, and by buying one you’ll be supporting this site – it’s win-win! If you happen to know a chemist, it would make a brilliant stocking-filler! As would a set of chemistry word magnets!

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. Content is © Kat Day 2020. You may share or link to anything here, but you must reference this site if you do. If you enjoy reading my blog, and especially if you’re using information you’ve found here to write a piece for which you will be paid, please consider buying me a coffee through Ko-fi using the button below.
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Want something non-sciency to distract you from, well, everything? Why not check out my fiction blog: the fiction phial.

Easy Indicators

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Indicator rainbow, reproduced with kind permission of Isobel Everest, @CrocodileChemi1

Recently on Twitter CrocodileChemist (aka Isobel Everest), a senior school science technician (shout out to science technicians, you’re all amazing) shared a fabulous video and photo of a “pH rainbow”.

The effect was achieved by combining various substances with different pH indicators, that is, substances that change colour when mixed with acids or alkalis.

Now, this is completely awesome, but, not something most people could easily reproduce at home, on account of their not having methyl orange or bromothymol blue, or a few other things (that said, if you did want to try, Isobel’s full method, and other indicator art, can be found here).

But fear not, I’ve got this. Well, I’ve got a really, really simple version. Well, actually, I’ve got more of an experiment, but you could make it into more of a rainbow if you wanted. Anyway…

This is what you need:

  • some red cabbage (one leaf is enough)
  • boiling water
  • mug
  • white plate, or laminated piece of white card, or white paper in a punched pocket
  • cling film/clear plastic wrap (if you’re using a plate)
  • mixture of household substances (see below)
  • board marker (optional) or pen
  • plastic pipettes (optional, but do make it easier – easily bought online)

First, make the indicator. There are recipes online, but some of them are over-complicated. All you really need to do is finely chop the red cabbage leaf, put it in a mug, and pour boiling water over it. Leave it to steep and cool down. Don’t accidentally drink it thinking it’s your coffee. Pour off the liquid. Done.

If you use a plate, cover it with cling film

Next, if you’re using a plate, cover it with cling film. There are two reasons for this: firstly, cling film is more hydrophobic (water-repelling) than most well-washed ceramic plates, so you’ll get better droplets. Secondly, if you write on a china plate with a board marker it doesn’t always wash off. Ask me how I know.

Next step: hunt down some household chemicals. I managed to track down oven cleaner, plughole sanitiser, washing up liquid, lemon juice, vinegar, limescale remover and toilet cleaner (note: not bleach – don’t confuse these two substances, one is acid, one is alkali, and they must never be mixed).

Label your plate/laminated card/paper in punched pocket with the names of the household substances.

Place a drop of cabbage indicator by each label. Keep them well spaced so they don’t run into each other. Also, at this stage, keep them fairly small. Leave one alone as a ‘control’. On my plate, it’s in the middle.

Add a drop of each of your household substances and observe the colours!

Red cabbage indicator with various household substances

IMPORTANT SAFETY NOTE: some of these substances are corrosive. The risk is small because you’re only using drops, but if working with children, make sure an adult keeps control of the bottles, and they only have access to a tiny amount. Drip the more caustic substances yourself. Take the opportunity to point out and explain hazard warning labels. Use the same precautions you would use when handling the substance normally, i.e. if you’d usually wear gloves to pick up the bottle, wear gloves. Some of these substances absolutely must not be mixed with each other: keep them all separate.

Here’s a quick summary of what I used:

A useful point to make here is that pH depends on the concentration of hydrogen ions (H+) in the solution. The more hydrogen ions, the more acidic the solution is. In fact, pH is a log scale, which means a change of x10 in hydrogen concentration corresponds to a change of one pH point. In short, the pH of a substance changes with dilution.

Compound Interest’s Cabbage Indicator page (click image for more info)

Which means that if you add enough water to acid, the pH goes up. So, for example, although the pH of pure ethanoic acid is more like 2.4, a dilute vinegar solution is probably closer to 3, or even a bit higher.

Compound Interest, as is usually the case, has a lovely graphic featuring red cabbage indicator. You can see that the colours correspond fairly well, although it does look like my oven cleaner is less alkaline (closer to green) than the plughole sanitiser (closer to yellow).

As the Compound Interest graphic mentions, the colour changes are due to anthocyanin pigments. These are red/blue/purple pigments that occur naturally in plants, and give them a few advantages, one of which is to act as a visual ripeness indicator. For example, the riper a blackberry is, the darker it becomes. That makes it stand out against green foliage, so it’s easier for birds and animals to find it, eat it and go on to spread the seeds. Note that “unripe” colours, yellow-green, are at the alkaline end, which corresponds to bitter flavours. “Ripe” colours, purple-red, are neutral to acidic, corresponding with much more appealing sweet and tart flavours. Isn’t nature clever?

You can make a whole mug full of indicator from a single cabbage leaf (don’t drink it by mistake).

Which brings me to my final point – what if you can’t get red cabbage? Supermarkets are bit… tricky at the moment, after all. Well, try with some other things! Any dark-coloured plant/fruit should work. Blueberries are good (and easy to find frozen). The skins of black grapes or the very dark red bit of a rhubarb stalk are worth a try. Blackberries grow wild in lots of places later in the year. Tomatoes, strawberries and other red fruits will also give colour changes (I’ve talked about strawberries before), although they’re less dramatic.

For those (rightly) concerned about wasting food – you don’t need a lot. I made a whole mug full of cabbage indicator from a single cabbage leaf, and it was the manky brown-around-the-edges one on the outside that was probably destined for compost anyway.

So, off you go, have fun! Stay indoors, learn about indicators, and stay safe.

EDIT: after I posted this, a few people tried some more experiments with fruits, vegetables and plants! Beaulieu Biology posted the amazing grid below, which includes everything from turmeric to radishes:

Image reproduced with kind permission of Beaulieu Biology (click for larger version)

And Compound Interest took some beautiful photos of indicator solutions extracted from a tulip flower, while CrocodileChemist did something similar and used the solutions to make a gorgeous picture of a tree. Check them out!

If you’re studying from home, have you got your Pocket Chemist yet? Why not grab one? It’s a hugely useful tool, and by buying one you’ll be supporting this site – it’s win-win!

Want something non-sciency to distract you? Why not check out my fiction blog: the fiction phial. There are loads of short stories, and even (recently) a couple of poems. Enjoy!

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. Content is © Kat Day 2020. You may share or link to anything here, but you must reference this site if you do. If you enjoy reading my blog, please consider buying me a coffee through Ko-fi using the button below.
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The Chronicles of the Chronicle Flask: 2018

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As has become traditional, I’m finishing off this year with a round-up of 2018’s posts. It’s been a good year: a few health scares which turned out to be nothing much to worry about, one which turned out to be a genuine danger, a couple of cool experiments and some spectacular shiny balls. So without further ado, here we go…

Things were a bit hectic at the start of this year (fiction writing was happening) and as a result January was quiet on the blog. But not on the Facebook page, where I posted a couple of general reminders about the silliness of alkaline diets which absolutely exploded, achieving some 4,000 shares and a reach (so Facebook tells me anyway) of over half a million people. Wow. And then I posted a funny thing about laundry symbols which went almost as wild. It’s a strange world.

February featured BPA: an additive in many plastics.

In February I wrote a piece about BPA (Bisphenol A), which was the chemical scare of the day. There’s always one around January/February time. It’s our penance for daring to enjoy Christmas. Anyway, BPA is a chemical in many plastics, and of course plastic waste had become – and remains – a hot topic. BPA is also used in a number of other things, not least the heat sensitive paper used to produce some shopping receipts. It’s not a harmless substance by any means, but it won’t surprise anyone to learn that the risks had, as is usually the case, been massively overstated. In a report, the European Food Safety Authority said that the health concern for BPA is low at their estimated levels of exposure. In other words, unless you’re actually working with it – in which case you should have received safety training – there’s no need to be concerned.

In March I recorded an episode for the A Dash of Science podcast, and I went on to write a post about VARD, which stands for Verify, Author, Reasonableness and Date. It’s my quick and easy way of fact-checking online information – an increasingly important skill these days. Check out the post for more info.

April ended up being all about dairy and vitamin D.

April was all about dairy after a flare-up on Twitter on the topic, and went on to talk about vitamin D. The bottom line is that everyone in the UK should be taking a small vitamin D supplement between about October and March, because northern Europeans simply can’t make vitamin D3 in their skin during these months (well, unless they travel nearer to the equator), and it’s not a nutrient we can easily get from our food. Are you taking yours?

May featured fish tanks, following a widely reported story about a fish-owner who cleaned out his tank and managed to release a deadly toxin that poisoned his entire family. Whoops. It turns that this was, and is, a real risk – so if you keep fish and you’ve never heard of this before, do have a read!

In June I wrote about strawberries, and did a neat experiment to show that strawberries could be used to make pH indicator. Who knew? You do, now! Check it out if you’re looking for some chemistry to amuse yourself over the holidays (I mean, who isn’t?). Did you know you can make indicators from the leaves of Christmas poinsettia plants, too?

Slime turned up again in July. And December. And will probably keep on rearing its slimy head.

July brought a subject which has turned up again recently: slime. I wrote about slime in 2017, too. It’s the gift that keeps on giving. This time it flared up because the consumer magazine and organisation Which? kept promoting research that, they claimed, showed that slime toys contain dangerous levels of borax. It’s all rather questionable, since it’s not really clear which safety guidelines they’re applying and whether they’re appropriate for slime toys. Plus, the limits that I was able to find are migration limits. In other words, it’s not appropriate to measure the total borax content of the slime and declare it dangerous – they should be looking at the amount of borax which is absorbed during normal use. Unless your child is eating slime (don’t let them do that), they’re never going to absorb enough borax to do them any harm. In other words, it’s a storm in a slimepot.

August was all about carbon dioxide, after a heatwave spread across Europe and there was, bizarrely, a carbon dioxide shortage which had an impact on all sorts of things from fizzy drinks to online shopping deliveries. It ended up being a long-ish post which spanned everything from the formation of the Earth, the discovery of carbon dioxide, fertilisers and environmental concerns.

September featured shiny, silver balls.

In September I turned my attention to a chemical reaction which is still to this day used to coat the inside of glass decorations with a thin layer of reflective silver, and has connections with biochemistry, physics and astronomy. Check it out for some pretty pictures of silver balls, and my silver nitrate-stained fingers.

In October I was lucky enough to go on a ‘fungi forage’ and so, naturally, I ended up writing all about mushrooms. Did you know that a certain type of mushroom can be used to make writing ink? Or that some mushrooms change colour when they’re damaged? No? You should go back and read that post, then! (And going back to April for a moment, certain mushrooms are one of the few sources of vitamin D.)

Finally, November ended up being all about water, marking the 235th anniversary of the day that Antoine Lavoisier formally declared water to be a compound. It went into the history of water, how it was proven to have the formula H2O, and I even did an experiment to split water into hydrogen and oxygen in my kitchen – did you know that was possible? It is!

As December neared, the research for my water piece led me to suggest to Andy Brunning of Compound Interest that this year’s Chemistry Advent might feature scientists from the last 24 decades of chemistry, starting in the 1780s (with Lavoisier and Paulze) and moving forward to the current day. This turned out to be a fantastic project, featuring lots of familiar and not quite so-familiar scientists. Do have a look if you didn’t follow along during December.

And that’s it for this year. I hope it’s been a good one for all my readers, and I wish you peace and prosperity in 2019! Suggestions for the traditional January Health Scare, anyone? (Let’s hope it’s not slime again, I’m getting really tired of that one now…)

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. All content is © Kat Day 2018. You may share or link to anything here, but you must reference this site if you do.

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Spectacular Strawberry Science!

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Garden strawberries

Yay! It’s June! Do you know what that means, Chronicle Flask readers? Football? What do you mean, football? Who cares about that? (I jest – check out this excellent post from Compound Interest).

No, I mean it’s strawberry season in the U.K.! That means there will be much strawberry eating, because the supermarkets are full of very reasonably-priced punnets. There will also be strawberry picking, as we tramp along rows selecting the very juiciest fruits (and eating… well, just a few – it’s part of the fun, right?).

Is there any nicer fruit than these little bundles of red deliciousness? Surely not. (Although I do also appreciate a ripe blackberry.)

And as if their lovely taste weren’t enough, there’s loads of brilliant strawberry science, too!

This is mainly (well, sort of, mostly, some of the time) a chemistry blog, but the botany and history aspects of strawberries are really interesting too. The woodland strawberry (Fragaria vesca) was the first to be cultivated in the early 17th century, although strawberries have of course been around a lot longer than that. The word strawberry is thought to come from ‘streabariye’ – a term used by the Benedictine monk Aelfric in CE 995.

Woodland strawberries

Woodland strawberries, though, are small and round: very different from the large, tapering, fruits we tend to see in shops today (their botanical name is Fragaria × ananassa – the ‘ananassa’ bit meaning pineapple, referring to their sweet scent and flavour.

The strawberries we’re most familiar with were actually bred from two other varieties. That means that modern strawberries are, technically, a genetically modified organism. But no need to worry: practically every plant we eat today is.

Of course, almost everyone’s heard that strawberries are not, strictly, a berry. It’s true; technically strawberries are what’s known as an “aggregate accessory” fruit, which means that they’re formed from the receptacle (the thick bit of the stem where flowers emerge) that holds the ovaries, rather than from the ovaries themselves. But it gets weirder. Those things on the outside that look like seeds? Not seeds. No, each one is actually an ovary, with a seed inside it. Basically strawberries are plant genitalia. There’s something to share with Grandma over a nice cup of tea and a scone.

Anyway, that’s enough botany. Bring on the chemistry! Let’s start with the bright red colour. As with most fruits, that colour comes from anthocyanins – water-soluble molecules which are odourless, moderately astringent, and brightly-coloured. They’re formed from the reaction of, similar-sounding, molecules called anthocyanidins with sugars. The main anthocyanin in strawberries is callistephin, otherwise known as pelargonidin-3-O-glucoside. It’s also found in the skin of certain grapes.

Anthocyanins are fun for chemists because they change colour with pH. It’s these molecules which are behind the famous red-cabbage indicator. Which means, yes, you can make strawberry indicator! I had a go myself, the results are below…

Strawberry juice acts as an indicator: pinky-purplish in an alkaline solution, bright orange in an acid.

As you can see, the strawberry juice is pinky-purplish in the alkaline solution (sodium hydrogen carbonate, aka baking soda, about pH 9), and bright orange in the acid (vinegar, aka acetic acid, about pH 3). Next time you find a couple of mushy strawberries that don’t look so tasty, don’t throw them away – try some kitchen chemistry instead!

Peonidin-3-O-glucoside is the anthocyanin which gives strawberries their red colour. This is the form found at acidic pHs

The reason we see this colour-changing behaviour is that the anthocyanin pigment gains an -OH group at alkaline pHs, and loses it at acidic pHs (as in the diagram here).

This small change is enough to alter the wavelengths of light absorbed by the compound, so we see different colours. The more green light that’s absorbed, the more pink/purple the solution appears. The more blue light that’s absorbed, the more orange/yellow we see.

Interestingly, anthocyanins behave slightly differently to most other pH indicators, which usually acquire a proton (H+) at low pH, and lose one at high pH.

Moving on from colour, what about the famous strawberry smell and flavour? That comes from furaneol, which is sometimes called strawberry furanone or, less romantically, DMHF. It’s the same compound which gives pineapples their scent (hence that whole Latin ananassa thing I mentioned earlier). The concentration of furaneol increases as the strawberry ripens, which is why they smell stronger.

Along with menthol and vanillin, furaneol is one of the most widely-used compounds in the flavour industry. Pure furaneol is added to strawberry-scented beauty products to give them their scent, but only in small amounts – at high concentrations it has a strong caramel-like odour which, I’m told, can actually smell quite unpleasant.

As strawberries ripen their sugar content increases, they get redder, and they produce more scent

As strawberries ripen their sugar content (a mixture of fructose, glucose and sucrose) also changes, increasing from about 5% to 9% by weight. This change is driven by auxin hormones such as indole-3-acetic acid. At the same time, acidity – largely from citric acid – decreases.

Those who’ve been paying attention might be putting a few things together at this point: as the strawberry ripens, it becomes less acidic, which helps to shift its colour from more green-yellow-orange towards those delicious-looking purpleish-reds. It’s also producing more furaneol, making it smell yummy, and its sugar content is increasing, making it lovely and sweet. Why is all this happening? Because the strawberry wants (as much as a plant can want) to be eaten, but only once it’s ripe – because that’s how its seeds get dispersed. Ripening is all about making the fruit more appealing – redder, sweeter, and nicer-smelling – to things that will eat it. Nature’s clever, eh?

There we have it: some spectacular strawberry science! As a final note, as soon as I started writing this I (naturally) found lots of other blogs about strawberries and summer berries in general. They’re all fascinating. If you want to read more, check out…

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Where did our love of dairy come from?

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The popularity of the soya latte seems to be on the rise.

A little while ago botanist James Wong tweeted about the myriad types of plant ‘milk’ that are increasingly being offered in coffee shops, none of which are truly milk (in the biological sense).

This generated a huge response, probably rather larger than he was expecting from an off-hand tweet. Now, I’m not going to get into the ethics of milk production because it’s beyond the scope of this blog (and let’s keep it out of the comments? — kthxbye) but I do want to consider one fairly long thread of responses which ran the gamut from ‘humans are the only species to drink the milk of another animal’ (actually, no) to ‘there’s no benefit to dairy’ (bear with me) and ending with, in essence, ‘dairy is slowly killing us‘ (complicated, but essentially there’s very little evidence of any harm).

Humans have been consuming dairy products for thousands of years.

But wait. If dairy is so terrible for humans, and if there are no advantages to it, why do we consume it at all? Dairy is not a new thing. Humans have been consuming foods made from one type of animal milk or another for 10,000 years, give or take. That’s really quite a long time. More to the point (I don’t want to be accused of appealing to antiquity, after all), keeping animals and milking them is quite resource intensive. You have to feed them, look after them and ensure they don’t wander off or get eaten by predators, not to mention actually milk them on a daily basis. All that takes time, energy and probably currency of some sort. Why would anyone bother, if dairy were truly detrimental to our well-being?

In fact, some cultures don’t bother. The ability to digest lactose (the main sugar in milk) beyond infancy is quite low in some parts of the world, specifically Asia and most of Africa. In those areas dairy is, or at least has been historically, not a significant part of people’s diet.

But it is in European diets. Particularly northern European diets. Northern Europeans are, generally, extremely tolerant of lactose into adulthood and beyond.

Which is interesting because it suggests, if you weren’t suspicious already, that there IS some advantage to consuming dairy. The ability to digest lactose seems to be a genetic trait. And it seems it’s something to do, really quite specifically, with your geographic location.

Which brings us to vitamin D. This vitamin, which is more accurately described as a hormone, is a crucial nutrient for humans. It increases absorption of calcium, magnesium and phosphate, which are all necessary for healthy bones (not to mention lots of other processes in the body). It’s well-known that a lack of vitamin D leads to weakened bones, and specifically causes rickets in children. More recently we’ve come to understand that vitamin D also supports our immune system; deficiency has been meaningfully linked to increased risk of certain viral infections.

What’s the connection between vitamin D and geographic location? Well, humans can make vitamin D in their skin, but we need a bit of help. In particular, and this is where the chemistry comes in, we need ultraviolet light. Specifically, UVB – light with wavelengths between 280 nm to 315 nm. When our skin is exposed to UVB, a substance called 7-dehydrocholesterol (7-DHC to its friends) is converted into previtamin D3, which is then changed by our body heat to vitamin D3, or cholecalciferol – which is the really good stuff. (There’s another form, vitamin D2, but this is slightly less biologically active.) At this point the liver and kidneys take over and activate the chloecalciferol via the magic of enzymes.

We make vitamin D in our skin when we’re exposed to UVB light.

How much UVB you’re exposed to depends on where you live. If you live anywhere near the equator, no problem. You get UVB all year round. Possibly too much, in fact – it’s also linked with skin cancers. But if you live in northerly latitudes (or very southerly), you might have a problem. In the summer months, a few minutes in the sun without sunscreen (literally a few minutes, not hours!) will produce more than enough vitamin D. But people living in UK, for example, get no UVB exposure for 6 months of the year. Icelanders go without for 7, and inhabitants of Tromsø, in Norway, have to get by for a full 8 months. Since we can only store vitamin D in our bodies for something like 2-4 months (I’ve struggled to find a consistent number for this, but everyone seems to agree it’s in this ballpark), that potentially means several months with no vitamin D at all, which could lead to deficiency.

In the winter northern Europeans don’t receive enough UVB light from the sun to produce vitamin D in their skin.

In the winter, northern Europeans simply can’t make vitamin D3 in their skin (and for anyone thinking about sunbeds, that’s a bad idea for several reasons). In 2018, this is easily fixed – you just take a supplement. For example, Public Health England recommends that Brits take a daily dose of 10 mcg (400 IU) of vitamin D in autumn and winter, i.e. between about October and March. It’s worth pointing out at this point that a lot of supplements you can buy contain much more than this, and more isn’t necessarily better. Vitamin D is fat-soluble and so it will build up in the body, potentially reaching toxic levels if you really overdo things. Check your labels.

Oily fish is an excellent source of vitamin D.

But what about a few thousand years ago, before you just could pop to the supermarket and buy a bottle of small tablets? What did northern Europeans do then? The answer is simple: they had to get vitamin D from their food. Even if it’s not particularly well-absorbed, it’s better than nothing.

Of couse it helps if you have access to lots of foods which are sources of vitamin D. Which would be…  fatty fish (tuna, mackerel, salmon, etc) – suddenly that northern European love of herring makes so much more sense – red meat, certain types of liver, egg yolks and, yep, dairy products. Dairy products, in truth, contain relatively low levels of vitamin D (cheese and butter are better than plain milk), but every little helps. Plus, they’re also a good source of calcium, which works alongside vitamin D and is, of course, really important for good bone health.

A side note for vegans and vegetarians: most dietry sources of vitamin D come from animals. Certain mushrooms grown under UV can be a good source of vitamin D2, but unless you’re super-careful a plant-based diet won’t provide enough of this nutrient. So if you live in the north somewhere or you don’t, or can’t, expose your skin to the sun very often, you need a supplement (vegan supplements are available).

Fair skin likely emerged because it allows for better vitamin D production when UVB levels are lower.

One thing I haven’t mentioned of course is skin-colour. Northern Europeans are generally fair-skinned, and this is vitamin D-related, too. The paler your skin, the better UVB penetrates it. Fair-skinned people living in the north had an advantage over those with darker skin in the winter, spring and autumn months: they could produce more vitamin D. In fact, this was probably a significant factor in the evolution of fair skin (although, as Ed Yong explains in this excellent article, that’s complicated).

In summary, consuming dairy does have advantages, at least historically. There’s a good reason Europeans love their cheeses. But these days, if you want to eat a vegan or vegetarian diet for any reason (once again, let’s not get into those reasons in comments, kay?) you really should take a vitamin D supplement. In fact, Public Health England recommends that everyone in the UK take a vitamin D supplement in the autumn and winter, but only a small amount – check your dose.

By the way, if you spot any ‘diary’s let me know. I really had to battle to keep them from sneaking in…

—

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Chemical du jour: how bad is BPA, really?

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BPA is an additive in many plastics

When I was writing my summary of 2017 I said that there would, very probably, be some sort of food health scare at the start of 2018. It’s the natural order of things: first we eat and drink the calorie requirement of a small blue whale over Christmas and New Year, and then, lo, we must be made to suffer the guilt in January. By Easter, of course, it’s all forgotten and we can cheerfully stuff ourselves with chocolate eggs.

Last year it was crispy potatoes, and the year before that it was something ridiculous about sugar in ketchup causing cancer (it’s the same sugar that’s in everything, why ketchup? Why?). This year, though, it seems that the nasty chemical of the day is not something that’s in our food so much as around it.

Because this year the villain of the piece appears to be BPA, otherwise known as Bisphenol A or, to give it its IUPAC name, 4,4′-(propane-2,2-diyl)diphenol.

BPA is an additive in plastics. At the end of last year an excellent documentary aired on the BBC called Blue Planet II, all about our planet’s oceans. It featured amazing, jaw-dropping footage of wildlife. It also featured some extremely shocking images of plastic waste, and the harm it causes.

Plastic waste is a serious problem

Plastic waste, particularly plastic waste which is improperly disposed of and consequently ends up in the wrong place, is indisputably something that needs to be addressed. But this highlighting of the plastic waste problem had an unintended consequence: where was the story going to go? Everyone is writing about how plastic is bad, went (I imagine) editorial meetings in offices around the country – find me a story showing that plastic is even WORSE than we thought!

Really, it was inevitable that a ‘not only is plastic bad for the environment, but it’s bad for you, too!’ theme was going to emerge. It started, sort of, with a headline in The Sun newspaper: “Shopping receipts could ‘increase your cancer risk’ – as 93% contain dangerous chemicals also linked to infertility. Shopping receipts are, of course, not made of plastic – but the article’s sub-heading stated that “BPA is used to make plastics”, so the implication was clear enough.

Then the rather confusing: “Plastic chemical linked to male infertility in majority of teenagers, study suggests” appeared in The Telegraph (more on this in a bit), and the whole thing exploded. Search for BPA in Google News now and there is everything from “5 Ways to Reduce Your Exposure to Toxic BPA” to “gender-bending chemicals found in plastic and linked to breast and prostate cancer are found in 86% of teenagers”.

Yikes. It’s all quite scary. It’s true that right now you can’t really avoid plastic. Look around you and it’s likely that you’ll immediately see lots of plastic objects, and that’s before you even try to consider all the everyday things which have plastic coatings that aren’t immediately obvious. If you have young children, you’re probably drowning in plastic toys, cups, plates and bottles. We’re pretty much touching plastic continually throughout our day. How concerned should we be?

As the Hitchiker’s Guide to the Galaxy says, Don’t Panic. Plastic (like planet Earth in the Guide) can probably be summed up as mostly harmless, at least from a BPA point of view if not an environmental one.

BPA is a rather pleasingly symmetrical molecule with two phenol groups. (A big model of this would make a wonderfully ironic pair of sunglasses, wouldn’t it?) It was first synthesized by the Russian chemist Alexander Dianin in the late 19th century. It’s made by reacting acetone – which is where the “A” in the name comes from – with two phenol molecules. It’s actually a very simple reaction, although the product does need to be carefully purified, since large amounts of phenol are used to ensure a good yield.

It’s been used commercially since the fifties, and millions of tonnes of BPA are now produced worldwide each year. BPA is used to make plastics which are clear and tough – two characteristics which are often valued, especially for things like waterproof coatings, bottles and food containers.

The concern is that BPA is an endocrine disruptor, meaning that it interferes with hormone systems. In particular, it’s a known xenoestrogen, in other words it mimics the female hormone estrogen. Animal studies have suggested possible links to certain cancers, infertility, neurological problems and other diseases. A lot of the work is fairly small-scale and, as I’ve mentioned, focused on animal studies (rather than looking directly at effects in humans). Where humans have been studied it’s usually been populations that are exposed to especially high BPA levels (epoxy resin painters, for example). Still, it builds up into quite a damning picture.

BPA has been banned from baby bottles in many countries, including the USA and Europe

Of course, we don’t normally eat plastic, but BPA can leach from the plastic into the food or drink that’s in the plastic, and much more so if the plastic is heated. Because of these concerns, BPA has been banned from baby bottles (which tend to be heated, both for sterilisation and to warm the milk) in several countries, including the whole of Europe, for some years now. “BPA free” labels are a fairly common sight on baby products these days. BPA might also get onto our skin from, for example, those thermal paper receipts The Sun article mentioned, and then into our mouths when we eat. Our bodies break down and excrete the chemical fairly quickly, in as little as 6 hours, but because it’s so common in our environment most of us are continually meeting new sources of it.

How much are we getting, though? This is a critical question, because as I’m forever saying, the dose makes the poison. Arsenic is a deadly poison at high levels, but most of us – were we to undergo some sort of very sensitive test – would probably find we have traces of it in our systems, because it’s a naturally-occuring mineral. It’s nothing to worry about, unless for some reason the levels become too high.

When it comes to BPA, different countries have different guidelines. The European Food Safety Authority recommended in January 2015 that the TDI (tolerable daily intake) should be reduced from 50 to 4 µg/kg body weight/day (there are plans for a new assessment in 2018, so it might change again). For a 75 kg adult, that translates to about 0.0003 g per day. A USA Federal Drug and Administration document from 2014 suggests a NOAEL (no-observed-adverse-effect-level) of 5 mg/kg bw/day, which translates to 0.375 g per day for the same 75 kg adult. NOAEL values are usually much higher than TDIs, so these two figures aren’t as incompatible as they might appear. Tolerable daily intake values tend to have a lot of additional “just in case” tossed into them – being rather more guidance than science.

The European Food Standards Authority published a detailed review of the evidence in 2015 (click for a summary)

So, how much BPA are we exposed to? I’m going to stick to Europe, because that’s where I’m based (for now…), and trying to look at all the different countries is horribly complicated. Besides, EFSA produced a really helpful executive summary of their findings in 2015, which makes it much easier to find the pertinent information.

The key points are these: most of our exposure comes from food. Infants, children and adolescents have the highest dietary exposures to BPA, probably because they eat and drink more per kilogram of body weight. The estimated average was 0.375 µg/kg bw per day.  For adult women the estimated average was 0.132 µg/kg bw per day, and for men it was 0.126 µg/kg bw per day.

When it came to thermal paper and other non-dietary exposure (mostly from dust, toys and cosmetics), the numbers were smaller, but the panel admitted there was a fair bit of uncertainty here. The total exposure from all sources was somewhere in the region of 1 µg/kg bw per day for all the age groups, with adolescents and young children edging more toward values of 1.5 µg/kg bw per day (this will be important in a minute).

Note that all of these numbers are significantly less than the, conservative, tolerable daily intake value of 4 µg/kg bw per day recommended by EFSA.

Here’s the important bit: the panel concluded that there is “no health concern for BPA at the estimated levels of exposure” as far as diet goes. They also said that this applied “to prenatally exposed children” (in other words, one less thing for pregnant women to worry about).

When it came to total exposure, i.e. diet and exposure from other sources such as thermal paper they concluded that “the health concern for BPA is low at the estimated levels of exposure”.

The factsheet that was published alongside the full document summarises the results as follows: “BPA poses no health risk to consumers because current exposure to the chemical is too low to cause harm.”

Like I said: Don’t Panic.

What about those frankly quite terrifying headlines? Well, firstly The Sun article was based on some work conducted on a grand total of 208 receipts collected in Southeast Michigan in the USA from only 39 unique business locations. That’s a pretty small sample and not, I’d suggest, perhaps terribly relevant to the readership of a British newspaper. Worse, the actual levels of BPA weren’t measured in the large majority of samples – they only tested to see if it was there, not how much was there. There was nothing conclusive at all to suggest that the levels in the receipts might be enough to “increase your cancer risk”. All in all, it was pretty meaningless. We already knew there was BPA in thermal receipt paper – no one was hiding that information (it’s literally in the second paragraph of the Wikipedia page on BPA).

The Telegraph article, and the many others it appeared to spawn, also weren’t based on especially rigorous work and, worse, totally misrepresented the findings in any case. Firstly, let’s consider that headline: “Plastic chemical linked to male infertility in majority of teenagers, study suggests”. What does that mean? Are they suggesting that teenagers are displaying infertility? No, of course not. They didn’t want to put “BPA” in the headline because that, apparently, would be too confusing for their readers. So instead they’ve replaced “BPA” with “plastic chemical linked to male infertility”, which is so much more straightforward, isn’t it?

And they don’t mean it’s linked to infertility in the majority of teenagers, they mean it’s linked to infertility and it’s in the majority of teenager’s bodies. I do appreciate that journalists rarely write headlines – this isn’t a criticism of the poor writer who turned in perfectly good copy – but that is confusing and misleading headline-writing of the highest order. Ugh.

Plus, as I commented back there, that wasn’t even the conclusion of the study, which was actually an experiment carried out by students under the supervision of a local university. The key finding was not that, horror, teenagers have BPA in their bodies. The researchers assumed that almost all of the teenagers would have BPA in their bodies – as the EFSA report showed, most people do. No, the conclusion was actually that the teenagers – 94 of them – had been unable to significantly reduce their levels of BPA by changing their diet and lifestyle. Although the paper admits the conditions weren’t well-controlled. Basically, they asked a group of 17-19 year-olds to avoid plastic, and worked on the basis that their account of doing so was accurate.

And how much did the teenagers have in their samples? The average was 1.22 ng/ml, in urine samples (ng = nanogram). Now, even if we assume that these levels apply to all human tissue (which they almost certainly don’t) and that therefore the students had roughly 1.22 ng per gram of body weight, that only translates to, very approximately, 1.22 micrograms (µg) per kilogram of body weight.

Wait a second… what did EFSA say again…. ah yes, they estimated total exposures of 1.449 µg/kg bw per day for adolescents.

Sooooo basically a very similar value, then? And the EFSA, after looking at multiple studies in painstaking detail, concluded that “BPA poses no health risk to consumers”.

Is this grounds for multiple hysterical, fear-mongering headlines? I really don’t think it is.

It is interesting that the teenagers were unable to reduce their BPA levels. Because it’s broken down and excreted quite quickly by the body, you might expect that reducing exposure would have a bigger effect – but really all we can say here is that this needs to be repeated with far more tightly-controlled conditions. Who knows what the students did, and didn’t, actually handle and eat. Perhaps their school environment contains high levels of BPA in dust for some reason (new buildings or equipment, maybe?), and so it was virtually impossible to avoid. Who knows.

In summary, despite the scary headlines there really is no need to worry too much about BPA from plastics or receipts. It may be worth avoiding heating plastic, since we know that increases the amound of BPA that makes its way into food – although it’s important to stress that there’s no evidence that microwaving plastic containers causes levels to be above safe limits. Still, if you wanted to be cautious you could choose to put food into a ceramic or glass bowl, covered with a plate rather than clingfilm. It’ll save you money on your clingfilm bills anyway, and it means less plastic waste, which is no bad thing.

Roll on Easter…

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. All content is © Kat Day 2018. You may share or link to anything here, but you must reference this site if you do.

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The Chronicles of the Chronicle Flask: 2017

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We’ve made it! Not only to 2018 (which was starting to look doubtful earlier in the year), but also to the Chronicle Flask’s 100th post. Which doesn’t seem that many, really, but since posts on here frequently run to 1500 words, that adds up to a rather more impressive-sounding 150,000 words or so. I mean, that’s like… half a Brandon Sanderson novel. Oh.

Anyway, it’s time for a yearly round-up. Here goes!

Last January I began with a post about acrylamide. We’d all been enjoying lots of lovely crispy food over Christmas; it was time to tell us about the terrible dangers of such reckless indulgence. The newspapers were covered with pictures of delicious-looking chips, toast and roast potatoes alongside scary headlines such as:  “Crunchy toast could give you cancer, FSA warns”. The truth was not quite so dramatic. Acrylamide does form when foods are cooked to crispiness, and it is potentially harmful, but the quantities which form in food are tiny, and very unlikely to cause you any serious harm unless you literally live on nothing but burnt toast. The FSA (Food Standards Agency) hadn’t significantly revised their guidelines, it turned out, but were in fact only suggesting that the food industry should be mindful of acrylamide levels in food and seek to reduce them as much as possible. That wouldn’t have made for quite such a good “your food is going to killllll you!” story though, I suppose.

In February the spikey topic of vaccination came up. Again. Vaccines are awesome. They protect us from deadly diseases. No, I don’t want to hear any nonsense about “Big Pharma“, and I definitely don’t want to hear how “natural immunity” is better. It’s not. At best, it might provide a similar level of protection (but not in every case), but it comes with having to suffer through a horrible, dangerous disease, whereas vaccination doesn’t. It ought to be a no-brainer. Just vaccinate your kids. And yourself.

It was Red Nose Day in the UK in March, which brought some chemistry jokes. Turns out all the best ones aren’t gone, after all. Did you hear about the PhD student who accidentally cooled herself to absolute zero? She’s 0K now.

April brought a post which ought to have been an April Fool’s joke, but wasn’t. Sceptics often point out that homeopathy is just sugar and water, but the trouble is, sometimes, it’s not. There’s virtually no regulation of homeopathy. As far as I’ve been able to establish, no one tests homeopathic products; no one checks the dilutions. Since a lot of the starting materials are dangerously toxic substances such as arsenic, belladona, lead and hemlock, this ought to worry people more than it does. There has been more than one accidental poisoning (perhaps most shockingly, one involving baby teething products). It really is time this stuff was banned, maybe 2018 will be the year.

In May I turned to something which was to become a bit of a theme for 2017: alkaline water. It’s not so much that it doesn’t do anything (although it really doesn’t), more the fact that someone is charging a premium for a product which you could literally make yourself for pennies. It’s only a matter of dissolving a pinch of baking soda (sodium bicarbonate) in some water.

June brought a selection of periodic tables because, well, why not? This is a chemistry blog, after all! And now we’ve finally filled up period seven they do have a rather elegant completness. 2019, by the way, has just been announced as the International Year of the Periodic Table of Chemical Elements, to coincide with IUPAC’s 100th anniversary and the 150th anniversary of Mendeelev’s discovery of periodicity (his presentation, The Dependence Between the Properties of of the Atomic Weights of the Elements, was made on 6th March 1869). Looks like 2019 will be an exciting year for chemists!

In July it was back to the nonsense of alkaline diets again, when Robert O. Young was finally sentenced to 3 years, 8 months in custody for conning vulnerable cancer patients into giving him large sums of money for ineffective and dangerous treatments. Good. Moving on.

August brought me back to a post that I’d actually started earlier in the year when I went to a March for Science event in April. It was all about slime, and August seemed like a good time to finally finish it, with the school holidays in full swing – what could be more fun on a rainy day at home than making slime? Slime was a bit of a 2017 craze, and there have been a few stories featuring children with severely irritated skin. But is this likely to be caused by borax? Not really. Turns out it’s actually very safe. Laundry detergents in general, not so much. In short, if you want to make slime the traditional way with PVA glue and borax, fill your boots. (Not really – your parents will be uninpressed.)

In September it was back to quackery: black salve. A nasty, corrosive concoction which is sold as a cancer cure. It won’t cure your cancer. It will burn a nasty great big hole in your skin. Do not mess with this stuff.

October carried on in a similar vein, literally. This time with a piece about naturopaths recommending hydrogen peroxide IVs as a treatment for lots of things, not least – you guessed it – cancer. Yes, hydrogen peroxide. The stuff you used to bleach hair. Intraveneously. Argh.

The puking pumpkin!

The end of the month featured a far better use for hydrogen peroxide, that of the puking pumpkin. Definitely one to roll out if, for any reason, you ever find yourself having to demonstrate catalysis.

November brought us, somewhat unseasonally, to tomatoes. Where is the best place to store them? Fridge or windowsill? Turns out the answer involves more chemistry than you might have imagined.

And then, finally, December. Looking for a last-minute Christmas gift? Why not buy a case of blk water? I mean, other than it’s an exorbitantly priced bottle of mysterious black stuff which doesn’t do any of the things it claims to do, and might actually get its colour from coal deposits, that is.

And that, dear friends and followers, is it for 2017! Happy New Year! Remember to be sceptical when the inevitable “deadly food” story appears in a few weeks….

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. All content is © Kat Day 2018. You may share or link to anything here, but you must reference this site if you do.

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Just what is blk water, and should you drink it?

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Christmas is almost here! Are you ready yet? Are you fed up with people asking if you’re ready yet? Have you worked out what to buy for Great-uncle Nigel, who says he neither needs nor wants anything? Always a tricky scenario, that. Consumables are often a safe fallback position. They don’t clutter up the house, and who doesn’t enjoy a nice box of luxury biscuits, or chocolates, or a bottle of champagne, or spirts, or a case of blk water.

Wait, what?

Yes, this mysterious product turned up in my feed a few weeks ago. It’s water (well, so they say), but it’s black. Actually black. Not just black because the bottle’s black, black because the liquid inside it is… black.

It’s black water.

A bit like… cola. Only blacker, and not fizzy, or sweet, or with any discernable flavour other than water.

It raises many questions, doesn’t it? Let’s start with why. Obviously it’s a great marketing gimmick. It definitely looks different. It also comes with a number of interesting claims. The suppliers claim it contains “no nasties” and “only 2 ingredients”, namely spring water and “Fulvic Minerals” (sic). (Hang on, I hear you say, if it’s minerals, plural, surely that’s already more than two ingredients? Oh, but that’s only the start. Stay with me.)

It claims to “balance pH levels” and help “to regulate our highly acidic diets”. Yes, well, I think I’ve covered that before. Absolutely nothing you drink, or eat, does anything to the pH in any part of your body except, possibly, your urine – where you might see a small difference under some circumstances (but even if you do it doesn’t tell you anything significant about the impact of your diet on your long-term health). And bear in mind that a few minutes after you drink any kind of alkaline water it mixes with stomach acid which has a pH of around 2. Honestly, none of that alkaline “goodness” makes it past your pyloric sphincter.

Finally, blk water apparently “replenishes electrolytes”. Hm. Electrolytes are important in the body. They’re ionic species, which means they can conduct electricity. Your muscles and neurons rely on electrical activity, so they are quite important. Like, life or death important. But because of that our bodies are quite good at regulating them, most of the time. If you run marathons in deserts, or get struck down with a nasty case of food poisoning, or have some kind of serious health condition (you’d know about it) you might need to think about electrolytes, but otherwise most of us get what we need from the food and drink we consume normally every day.

Besides which, didn’t they say “only 2 ingredients”? The most common electrolytes in the body are sodium, potassium, magnesium, chloride, hydrogen phosphate and hydrogen carbonate. Most spring waters do contain some, if not all, of these, in greater or smaller amounts, but it’s not going to be enough to effectively “replenish” any of them. If, say, you are running marathons in the desert, the advice is actually to keep a careful eye on your water intake because drinking too much water can dangerously lower your sodium levels. Yes, there are sports drinks that are specifically designed to help with this, but they taste of salt and sugar and/or flavourings which have been added in a desperate attempt to cover up the salty taste. This is apparently not the case with blk water which, to repeat myself, contains “only 2 ingredients”.

And, according to the blk website the drink contains “0 mg of sodium per 500ml” so… yeah.

Speaking of ingredients, what about those so-called fulvic minerals? Maybe they’re the source of those all-important electrolytes (but not sodium)? And maybe they’re magically tasteless, too?

And perhaps, like other magical objects and substances, they don’t actually exist – as geologist @geolizzy told me on Twitter when I asked.

It’s not looking good for blk water (£47.99 for a case of 24 bottles) at this point. But hang on. Perhaps when they said fulvic minerals, what they meant was fulvic acid – which is a thing, or possibly several things – in a the presence of oh, say, some bicarbonate (*cough* 2 ingredients *cough*).

That could push the pH up to the stated 8-9, and didn’t we learn in school that:
acid + alkali –> salt + water
and maybe, if we’re being generous, we could call the salts of fulvic acids minerals? It’s a bit shaky but… all right.

So what are fulvic acids?

That’s an interesting question. I had never heard of fulvic acids. They do, as it turns out, have a Wikipedia page (Wikipedia is usually very reliable for chemical information, since no one has yet been very interested in spoofing chemical pages to claim things like hydrochloric acid is extracted from the urine of pregnant unicorns) but the information wasn’t particularly enlightening. The page did inform me that fulvic acids are “components of the humus” (in soil) and are  “similar to humic acids, with differences being the carbon and oxygen contents, acidity, degree of polymerization, molecular weight, and color.” The Twitter hive-mind, as you can see, was sending me down the same path…

A typical example of a humic acid.

Next stop, humic acids. Now we’re getting somewhere. These are big molecules with several functional groups. The chemists out there will observe that, yes, they contain several carboxylic acid groups (the COOH / HOOC ones you can see in the example) so, yes, it makes sense they’d behave as acids.

“No nasties”, blk said. “Pure” they said. When you hear those sorts of things, do you imagine something like this is in your drink? Especially one that, let’s be clear, is a component of soil?

Oh, hang on, I should’ve checked the “blk explained” page on the blk water website. There’s a heading which actually says “what are Fulvic Minerals”, let’s see now…

“Fulvic minerals are plant matter derived from millions of years ago that have combined with fulvic acid forming rare fulvic mineral deposits. They deliver some of the most powerful electrolytes in the world.”

“Fulvic minerals contain 77 other trace minerals, most of which have an influence on the healthiness of our body. They are very high in alkaline and when sourced from the ground contain a pH of 9.”

I don’t know about you, but I’m not totally convinced. I mean, as @geolizzy says in her tweet here (excuse the minor typo, she means humic, not humid),  it sounds a bit like… water contaminated with hydrocarbon deposits?

Yummy.

And, by the way, the phrase “very high in alkaline” is utterly meaningless. Substances are alkaline, or they contain substances which are alkaline. “Alkaline” is not a thing in itself. This is like saying my tea is high in hot when sourced from the teapot.

There’s one more thing to add. So far this might sound a bit weird but… probably safe, right? What could be more wholesome than a bit of soil? Didn’t your granny tell you to eat a pinch of soil to boost your immune system, or something? At worst it’s harmless, right?

Tap water is chlorine-treated to keep it free of nasty bacteria.

Maybe. But then again… water is often treated with chlorine compounds to keep it bacteria-free. Now, blk water is supposedly spring water, which isn’t usually treated. But hypothetically, let’s consider what happens when humic acids, or fulvic acids, or whatever we’re calling them, come into contact with chlorine-treated water.

Oh dear. It seems that dihaloacetonitriles are formed. (See also this paper.) This is a group of substances (possibly the best known one is dichloroacetonitrile) which are variously toxic and mutagenic. Let’s hope that spring water is totally unchlorinated, 100% “we really got it from out of a rock” spring water, then.

To sum up: it is black, and that’s kind of weird and a fun talking point – although if you like the idea of a black drink you can always drink cola. It doesn’t balance your pH levels – nothing does. I don’t believe it replenishes electrolyte levels either – how can it when it doesn’t contain sodium? – and I’m dubious about the “2 ingredients” claim (could you tell?). And the oh-so-healthy-sounding fulvic minerals are most likely due to contamination from coal deposits.

All in all, whilst it might not be quite such a conversation piece, I think it would be better to get Great-uncle Nigel a nice box of chocolates this year.

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In the fridge or on the windowsill: where’s the best place to keep tomatoes?

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Fresh fruit and vegetables are great, but where’s the best place to store them?

I’ve mentioned before that my Dad is a professional plant-wrangler (if you’ve never read the electric daisies post, do go and have a look – it’s a little-read favourite) and he often brings me home-grown fruit and vegetables.

What follows is an inevitable disagreement about storage, specifically, my habit of putting everything in the fridge.

In my defence, modern houses rarely have pantries (boo) and we don’t even have a garage. We do have a shed, but it’s at the bottom of our poorly-lit, somewhat muddy garden. Do I want to traipse out there on a cold, dark, autumn evening? No, I do not. So the fabled “cool, dark place” is a bit of problem. My fridge is cool and dark, I have argued, but here’s the thing – turns out, it’s too cool. And quite probably too dark.

This I have learned from the botanist James Wong (@botanygeek on Twitter), whose talk I attended on Monday this week at the Mathematical Institute in Oxford. James, it turns out, had a rather similar argument with his Mum, particularly regarding tomatoes.

We should’ve listened to out parents, because they were right. A lot of fruit and vegetables really are better stored outside of the fridge, and for tomatoes in particular “better” actually means “more nutritious”.

Lycopene is a very long molecule with lots of double C=C bonds.

Tomatoes, James explained, contain a lot of a chemical called lycopene. It’s a carotene pigment, and it’s what gives tomatoes their red colour.

Lycopene has lots of double bonds between its carbon atoms which form something chemists call a conjugated system. This has some rather cool properties, one of which is an ability to absorb certain wavelengths of light. Lycopene is especially good at absorbing blue and green wavelengths, leaving our eyes to detect the red light that’s left.

Lycopene absorbs blue and green light, which is why tomatoes appear red.

Tomatoes and lycopene also seem to have a lot of health benefits. There’s some evidence that lycopene might reduce the risk of prostate and other cancers. It also appears to reduce the risk of stroke, and eating tomato concentrate might even help to protect your skin from sun damage (don’t get any ideas, you still need sunblock). Admittedly the evidence is currently a bit shaky – it’s a case of “more research is needed” – but even if it turns out to that the causative relationship isn’t terribly strong, tomatoes are still a really good source of fibre and vitamins A, C and E. Plus, you know, they taste yummy!

But back to the fridge. Surely they will keep longer in the fridge, and the low temperatures will help to preserve the nutrients? Isn’t that how it works?

Well, no. As James explained, once tomatoes are severed from the plant they have exactly one purpose: to get eaten. The reason, from the plant’s point of view, is that the critter which eats them will hopefully wander off and – ahem – eliminate the tomato seeds at a later time, somewhere away from the parent plant. This spreads the seeds far and wide, allowing little baby tomato plants to grow in a nice, open space with lots of water and sun.

For this reason once the tomato fruit falls, or is cut, from the tomato plant it doesn’t just sit there doing nothing. No, it carries on producing lycopene. Or rather, it does if the temperature is above about 10 oC. Below that temperature (as in a fridge), everything more or less stops. But, leave a tomato at room temperature and lycopene levels increase significantly. Plus, the tomato pumps out extra volatile compounds – both as an insect repellant and to attract animals which might usefully eat it – which means… yes: room temperature tomatoes really do smell better. As if that weren’t enough, chilling tomatoes can damage cell membranes, which can actually cause them to spoil more quickly.

In summary, not only will tomatoes last longer out of the fridge, they will actually contain more healthy lycopene!

Anecdotally, once I got over my scepticism and actually started leaving my tomatoes on my windowsill (after years of refrigeration) I discovered that it’s true. My windowsill tomatoes really do seem to last longer than they used to in the fridge, and they almost never go mouldy. Of course, it’s possible that I might not be comparing like for like (who knows what variety of tomato I bought last year compared to this week), but I urge you to try it for yourself.

James mentioned lots of other interesting bits and pieces in his talk. Did you know that sun-dried shiitake mushrooms are much higher in vitamin D? Or that you can double the amount of flavonoid you absorb from your blueberries by cooking them? (Take that, raw food people!) Storing apples on your windowsill is likely to increase the amount of healthy polyphenols in their skin, red peppers are better for you than green ones, adding mustard to cooked broccoli makes it more nutritious, and it would be much better if we bought our butternut squash in the autumn and saved it for Christmas – it becomes sweeter and more flavoursome over time.

In short, fascinating. Who wants to listen to some “clean eater” making it up as they go along when you can listen to a fully-qualified botanist who really knows what he’s talking about? Do check out the book, How to Eat Better, by James Wong – it’s packed full of brilliant tidbits like this and has loads of recipes.

And yes, Dad: you were right.

Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. All content is © Kat Day 2017. You may share or link to anything here, but you must reference this site if you do.

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