Chocs Away!

Chocolate has long been a passion of mine. So much so that my GCSE English speaking presentation was on the subject. Sadly for me, but fortunately for you, dear reader, the content of said work has long been lost somewhere in the unsalvageable hard drive of an ancient computer, so cannot be easily regurgitated here. However, morsels still remain in my memory and my alleged development as a scientific researcher may help in producing something ever-so-slightly better than my 16 year-old self could manage. Although I gave out actual chocolate samples in my presentation, so I am not entirely sure about that…

I’ll start with a little bit of botany, with a twist of geography for good measure. Chocolate is made using the beans from the cocoa tree, Theobroma cacao. This is indigenous to the Central and Southern American tropics and is one of 22 species of Theobroma, whose name means “food of the Gods.” You will possibly have seen a specimen at the Botanical Gardens, or on your Gap Yah, if you did such a thing. Recently, scientists have been using genetics in order to track the spread of plant and its cultivation and domestication. They have found 10 distinct genetic clusters, separated largely by geography. Interestingly, the most genetic diversity is found in the Upper Amazon region, indicating that this is where the species originated. However, the question of when the tree was domesticated and cultivated for use is a contentious issue, but vessels which could have been used for an early version of the fermented cacao drink favoured by the Aztecs have been dated back to approximately 3500 years ago. However, this may not signify true domestication, rather semi-cultivation. Some rather excellent scientists who use analytical chemistry to analyse ancient pottery and have found that dry residue from Mokayan (Mesoamerican settled villagers) pottery vessels contained theobromine, which is a remarkable compound found in chocolate (see below) and a clear indicator of its presence. These vessels were dated from around 1900BC, so it’s clear that chocolate has been used in one form or another for a very long time.

The Spanish Conquest of South America resulted in the spread of chocolate to Europe and beyond. Upon their arrival, Cortez et al will have found a very different form of chocolate to that which we are used to today. The Aztecs tended to use their chocolate in drinks, in which the beans were ground, mixed with maize and peppers and fermented, which must have been a strain on the European palate. Having said that, many Europeans (Brits, I’m looking at us) are known for a taste for alcohol so it might not have gone down too badly! However, upon coming to Europe, chocolate was, although still used as a drink, more often mixed with vanilla and sugar to make it more palatable. The production of solid chocolate in Britain began in the 18^th Century, and involves more interesting science.

The production of chocolate requires extreme precision. There are a number of processes the cocoa beans must go through to be turned from brown, shrivelled, bitter droppings into velvety smooth richness, each of which has a specific purpose. After they have been harvested, the beans are fermented and dried, giving them their dark brown colour. They are then roasted to intensify their flavour, before winnowing to remove the edible nibs from their husk. These nibs are ground to form cocoa liquor, or cocoa mass, which is processed further to give two separate products: cocoa butter, used in chocolate, and cocoa presscake, which forms cocoa powder. The cocoa butter is mixed with additional cocoa liquor to form chocolate and has to undergo substantial processing to achieve the correct consistency and flavour, which is where the science comes in. The chocolate must first be conched, which is much like kneading and serves to effectively emulsify the fats within the chocolate, meaning that the cocoa butter is evenly distributed throughout. Furthermore, this process helps to develop flavour by eliminating some unwanted chemicals, such as acetic and butyric acids. The conching is done at a temperature specific to the chocolate being made (49-82⁰C), with higher temperatures reserved for darker chocolate. A higher temperature promotes the Maillard reaction, which results in a caramelised flavour in many foods. Amino acids and sugars react to form many different flavour compounds unique to the food undergoing the reaction.

After conching, the chocolate is tempered, which is another temperature controlled-process. This is of importance to the texture, rather than flavour, of the finished product. The melted chocolate must be cooled to 28⁰C, heated again to a temperature specific to the type of chocolate you are using (27-32⁰C). This is because chocolate crystallises in six different forms, and only one of these gives the right texture to give the smooth,  shiny, snappable product we (I) expect. This form is the beta form, or form V, and consists of small crystals. All of the other forms give a crumbly, rough, dull mess. Chocolate that isn’t “in temper”-as the pros call it- also suffers from the phenomenon known as fat bloom, where the fats rise to the surface and cause a streaky, mottled, dullness. A similar phenomenon occurs in my brain from time-to-time, I’m sure.

The production of chocolate clearly involves some fascinating scientific morsels, but there is also a lot of great science to be found within the reason for its sheer excellence: its exquisite taste. Chocolate is home to 600 volatile flavour compounds, which contribute to its unique flavour. 25 of these were found to be at a high enough concentration to be recognised by human olfactory receptors. These comprise of some very odd compounds which one would not necessarily associate with the flavour of chocolate, such as dimethyl trisulfide, which smells like cooked cabbage and 2- and 3-methylbutanoic acids which both smell rather sweaty. Dr Peter Schieberle, a researcher at Munich Technical University, found that combining these 25 compounds produced an aroma which was able to be identified by humans as chocolate! Fascinatingly, the interaction of just 4% of the flavour compounds found in chocolate with the olfactory neurons is sufficient to convince the human brain that it is smelling chocolate. Schieberle intends to use his work to tweak the chocolate making process in order to improve its flavour profile. I didn’t stumble across much about the other 575 flavour compounds in my (extensive and laborious-ish) research, but I am guessing that they all contribute to the unique tastes of different blends and brands. Something to look into on a rainy day, perhaps?

The flavour compounds in chocolate aren’t the only interesting ones it contains. I mentioned theobromine above, which is a signature compound of chocolate. This is a xanthine alkaloid, meaning that it belongs to the same chemical family as caffeine and is also a metabolite of caffeine, which is broken down by the liver into theophylline, theobromine and paraxanthine. Much like caffeine, it is a diuretic and a vasodilator (widens blood vessels). The compound was discovered in 1841 by Alexander Voskresensky and its vasodilatory properties mean that it has been used to treat high blood pressure, as well as arteriosclerosis (clogged arteries) and angina. So you read it here first- chocolate is good for you! It’s also an aphrodisiac- wink wink- and a reason why dogs and cats shouldn’t eat chocolate. They metabolise theobromine slowly, so the accumulation poisons them. Not so great.

Theobromine

There is so much more to explore regarding chocolate and health, as well as the science behind all aspects of this wonderful stuff, but I’ll let you have a break. I hope you have enjoyed my bounteous knowledge on the subject. To those of you who have reached the bitter end, I salute you. Hopefully now you will be chock full of fantastic facts with which to bore all of the people who leave a bitter taste in your mouth. Until next time… chocks away!

References:

Powis, T.G., et al, Antiquity, 2007, 81 (314) http://antiquity.ac.uk/projgall/powis/index.html, Clement, C.R. et al, Diversity, 2010 2, 72-106; doi:10.3390/d2010072

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003311
http://www.sfu.ca/geog351fall03/groups-webpages/gp8/prod/prod.html
http://www.icco.org/about-cocoa/processing-cocoa.html
http://www.scientificamerican.com/article/sensomics-chocolate-smell/
Dr Peter Schieberle presented his work at a meeting of the American Chemical Society: http://www.acs.org/content/acs/en/pressroom/newsreleases/2011/august/whats-really-in-that-luscious-chocolate-aroma.html

Pongy Ponderings

This is a bit of a cheat, but here is an article I wrote for my college magazine (following "Going Bananas"). I thought it was about time I added to my oeuvre and posted it up here. Enjoy!

Commissioned once again by our illustrious editor to get my geek on and bring more pithy and zesty morsels (see what I did there?) of culinary science to the discerning readers of Linacre, I happily agreed, confident that my ability to bulls**t about things I really know nothing of had not deserted me or been used up on my extended essay. However, later contemplation served to instil a deep and very real fear, nay, panic. Writer’s block! How to top the giddy heights of last term’s column, for which I had received such compliments as “I like bananas,” and “I saw your name- I’ll read it later?” What subject could possibly provide as much entertainment and pure comedy as the banana, that funniest of foods; comic trope and device recognised internationally as truly hilarious? The answer, I realised, with a sinking feeling in my stomach, is nothing. So, like the inferior second season of a once- sparkling sitcom, clearly acknowledging that I have peaked but desperately clinging to one last shot in a ratings war which I will surely lose, I am opting for the easy way out: gross-out humour. The last resort of the desperate comedian. There is no dignity in this, but, as our aforementioned illustrious editor has pointed out, my sense of humour is akin to that found in a 12 year old boy, so I know that I am not above this task. Therefore, the subject of this lacklustre, trying-too-hard and probably not even remotely interesting (it’s page-filler, basically) article is the science of smelly food.

Improbable as it may seem, there are actually quite a number of scientists who trouble themselves professionally with this, delving into their compost bins and furking about in the bottom of the fridge (well, I imagine it’s actually a bit more sophisticated than that, but you get my drift) to find out what the molecular source of the pongs and whiffs therein actually is. Onions and garlic are extremely popular amongst sulfur chemists, although I imagine not with their significant others, as the cause of their odour is a family of sulfur-containing compounds which are modified during cooking to alter the smell from eye-wateringly offensive to mouth-wateringly appetising. In the 1980s, scientists found that the compound in raw onions with which this odorous journey begins is an amino acid derivative called propenyl cysteine sulfoxide. Slicing the onion exposes this unfortunate chemical to an enzyme called alliinase, which breaks it down into propenesulfenic acid and the mayhem begins. Two molecules of propenesulfenic acid can combine to produce thiosulfinate which is responsible for that pungent raw onion smell, whilst cooking produces the taste bud-tingling aroma of bispropenyl disulfide. (On a side note, it is very pleasing to meet a pleasant-smelling sulfur compound. I am currently working with carbon disulfide and as such am the least popular chemist in my lab. **Sob** I can only imagine what the guys who work on this onion and garlic business go through. They must be even less popular than the physicists.)

So, that’s the vegetables, but what about the smelly proteins? Meat, fish and eggs all suffer from their own personal hygiene issues, as it were. In the case of eggs, the culprit is once again sulfur, in the form of hydrogen sulfide (H₂S), and this is not only found in rotten eggs. According to eHow (yes, my research methods are once again exemplary), boiling eggs the wrong way can also cause a pongy problem. Overcooking produces excess hydrogen sulfide, which reacts with iron in the egg yolk. This is the cause of the smell and also of the greenish colour that rings the egg yolk of an imperfectly hard-boiled egg. Good to know. On another side note, typing “rotten egg smell” into Google turned up this rather wonderful gem from The Independent: “How the smell of rotten eggs makes men randy.”  That’s right. Apparently, tiny quantities of hydrogen sulfide are released in penile nerve cells and may stimulate an erection, which could present an alternative treatment route for people suffering from erectile dysfunction who don’t respond to Viagra. I’ll let you form your own opinions about this, but if you are, by any chance, interested a) don’t tell anyone- they may make certain assumptions and b) look the paper up- it’s been published in PNAS (that’s the Proceedings of the National Academy of Sciences).

Well, that was quite a detour, so back to the original point. At this juncture we wish sulfur farewell, as there are other molecular offenders who deserve a little mention in this missive. The chemicals responsible for the stomach-turning smell of rotten meat and fish and pungent cheese are, in fact, nitrogen-containing. Fish flesh contains a compound called trimethylamine oxide, which is broken down upon decomposition to give nasty smelling tri- and dimethylamine, making it very easy to tell whether the fishmonger was lying or not when he told you that the fish you bought was freshly caught 3 hours ago, but very difficult to make your fridge smell nice again. Likewise, the nitrogen-containing molecule present in rotting flesh of the meat variety is aptly (but disturbingly) named cadaverine and is a diamine produced upon the breakdown of the amino acid lysine. And we have all experienced the gag-inducing whiff of ammonia (NH₃) emanating from a somewhat over-ripe wheel of brie. I am not only beginning to feel very sorry for the sad reputation sulfur has despite nitrogen’s equal culpability in this field, but also praying to the chemistry gods (or my supervisor) that I don’t have to start working with amines any time soon.

So there we have it, dear reader. Apologies if you began reading this column over breakfast (particularly if that breakfast contained fish or eggs). I hope that, in such a case, you can forgive me for this woeful attempt at a follow-up on the glory days of Hilary term and take comfort in the fact that you will be beginning your day marginally better informed on a subject with no practical use whatsoever. That’s kind of how I feel about my PhD… 

Burnt Offering

Oh it’s been one of those days. Everything that could go did go wrong. So to try to salvage something of the day and not start November with a complete and utter fail, I thought I’d use the next hour I have to wait before I can do anything to the (probably failed) peptides I have (not) managed to make today writing something interesting. On the plus side, I get a witty title out of it- let’s view this as an offering to the Gods of Science to get them back on my side so that they will make my experiments work again! It’s worth a try.

As I am in the lab, I thought that I would take something lab-related as my inspiration, so today I will be focussing on the all-out baddy and the compound we all love to hate, acrylamide. You may be familiar with the name due to the abundance of articles in the press about how bad burnt/roasted/cooked food is for you and how it will give you cancer. I know about it because my lab uses acrylamide on a day-to-day basis to make things called SDS PAGE gels. SDS PAGE stands for Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis and is an incredibly clever and useful technique used to separate proteins. So it’s not really a complete baddy. It’s just all about context.

Let’s start with the good side of acrylamide: PAGE. PAGE is a fantastic technique and has lots of applications. Basically, a gel made from polymerised acrylamide (lots of molecules of acrylamide joined together to make a large structure) is made between two glass plates. Samples of protein which have been denatured using various chemicals and heating are loaded into wells in the top of the plate and a charge is applied across the plate so that the top is negatively charged and the bottom is positively charged. The denatured protein is negatively charged, so moves towards the bottom of the plate. The size of the protein determines how far it moves through the gel, so it will be deposited as a band at a particular point on the gel, which will show up in a rather fetching shade of blue when stained with a special protein stain. If you also load a reference mixture with pre-stained proteins of known molecular weight, you can compare the protein you are investigating to the reference and see what molecular weight your protein is, whether your samples contain a mixture of protein and if you have what you want. Which is great. Plus the gels can look really pretty. Usually prettier than this:

 So far so useful. But what about the bad side? And how is this related to food? I promise that there is a point, which I will be getting to rather shortly. As in now. Acrylamide is really blooming toxic. It’s a neurotoxin, which means it affects the nervous system and disrupts major signalling pathways in the body which really aren't meant to be disrupted. We aren't allowed to use it as a powder in the lab in case we inhale it and die. It’s less toxic as a liquid and when it’s part of a gel (unless you decide that to eat it) and we all have to treat it with care and follow all of the excellent safety procedures we have in place for using it to avoid nasty accidents.

Unfortunately, as I alluded to in the introduction to this post, acrylamide is practically everywhere in the world of food. It is made due to the oxidation of the amino acid asparagine, which occurs at high temperatures¹ and is found in foods which are high in starch and, according to the Food Standards Agency, baked, fried, grilled or roasted². So basically all cooked foods. Yay.

The risk was first identified by scientists in Sweden in the late 1990s and prompted an enormous number of studies, reviews and comment in both the scientific literature and standard press. If you type “acrylamide food” into PubMed you get 1009 hits and it’s not surprising. Acrylamide was already known to cause cancer in mice and so had been classified as a possible human carcinogen³. The way in which it is proposed to cause damage is by being metabolised to form an epoxide called glycidamide, which is a very reactive species containing oxygen in a three-membered ring. Epoxides are generally bad news in the body, as they react with DNA. This can cause problems with the regulation of cell replication and lead to uncontrolled cell proliferation, which is one of the key features of cancer. A very clever study by the Swedish scientists⁴ made use of the fact that acrylamide also binds to the N-terminal amino acid valine (ie. nitrogen-containing end) in haemoglobin to form an adduct called CEV (N-(2-carbamoylethyl)-valine, which allows background levels of acrylamide in the body to be assessed. The team fed some rats a diet which was high in fried foods and had a control group of rats fed on a diet of unfried food. They found much higher levels (almost 10-fold) of CEV in the rats fed on a fried diet than those in the control group, meaning that fried foods did seem to be causing increased levels of acrylamide in the body. A later study in 2002 by Rosen et al found high levels of acrylamide in foods such as crisps, bread and cereals⁵. Since then, the major culprits have commonly been found to be bread, fried potato products, baked goods and coffee. How upsetting.

However, there is no need to panic yet! Lots of agencies, including the WHO, European Commission and European Food Safety Authority have been working on this for some time and have been developing codes of practice and better knowledge about acrylamide levels in food. Right now, all they recommend is that acrylamide levels in processed foods be as low as possible, and that when you are making chips or toast you make them as pale as acceptably possible to reduce acrylamide levels²-the burnt stuff is particularly bad (see title!).  Which is no fun, but probably worthwhile. A lot of work is being done to make more sense of the link between acrylamide and cancer, as the data so far is unclear⁶. It’s fair to say that enjoying a balanced diet and minimising your intake of starchy fried goods can be no bad thing, but right now the jury is out on just how much acrylamide is safe to consume without increasing the risk of cancer. I'm not trying to preach here, not least because I am the first one to be found eating a chip butty with a cup of coffee on the side, but it is something to bear in mind.

I’m always fascinated by the dual personalities found in science. The everyday objects of the lab can be extremely harmful if treated without respect or if they turn up in significant amounts in the wrong place. The story of acrylamide, in particular, also shows that there are lots and lots of really clever scientists out there studying what we eat in minute detail and having a huge impact on public health. ‘Cooking a fry-up for rats’ may have sounded a little bit bonkers to a lot of people at the time, but the outcomes of the study have led to some really serious work and a much better understanding of how what we put in our mouths affects our bodies in a very real and sometimes quite scary way. There’s still work to be done on this and so much more. So get out there, all of you sciency people, and keep finding it out. Then let the rest of us know what you find.

Addendum: Monday 4^th November. I checked my peptides-they didn't work. Even my really pretty interesting blog post (!) couldn't please the Science Gods. Apparently science doesn't work like that. Oh well, maybe next time…

References:

1)      Tareke, E. et al, J Agric Food Chem. 2009,57(20):9730-3.

2)      http://www.food.gov.uk/policy-advice/acrylamide_branch/#.Unfrr_mcdng

3)      Orellana, C. Lancet Oncol. 2002, 3(6):325.

4)      Tareke, E. et al. Chem Res Toxicol. 2000, 13 (6):517-22.

5)      Rosén, J. and    Hellenäs, K.E.  Analyst, 2002,127, 880-882

6)      Pedreschi, F. et al J Sci Food Agric. 2013 Aug 12. doi: 10.1002/jsfa.6349. [Epub ahead of print]

Have you "herb" the latest...?

Somewhat (un)shockingly, it has been over 6 months since I last wrote anything on here. I’m not going to apologise. I believe that anyone who reads this is already so accustomed to my guilt-ridden introductions that they will know how I feel about this. And if they are still reading my posts, then I will hazard a guess that they forgive me for it and just want me to get on with it.

As I approach the end of the first year of my DPhil (gulp-how did that happen?), I have been afforded a rare and unusual pleasure- a day off. But as we all know, a day off does not really mean a day off. It means catching up on all of the admin that you’ve been ignoring, planning for the year ahead and sorting things around the house that really should have been done by now (we moved in 2 months ago). However, in amongst all of this, I have managed to find the time to do four pleasant things:

1)      Go for a walk in the park. It’s a beautiful, crisp Autumn day and staying inside would have been a sin.

2)      Catch up with a lovely friend via a Skype chat.

3)      Plant some herbs to grow in our (ahem) conservatory.

4)      Write that blog post I’ve been meaning to write for ages.

The observant amongst you may notice something food related in that list and hence not be surprised when I reveal that the subject of this post is herbs. Or something like that. We’ll see how we go.

I love to use herbs in my cooking. I recently heard the term “flavour magpie” and think that it very accurately describes my style of cooking. If I haven’t thrown some herbs or spices into a pot somewhere during the preparation of a meal, then I’m probably cooking outdoors somewhere with only a trangia stove and instant mashed potato for company and inspiration. I’m also likely to be desperately unhappy and fantasising about what I COULD be eating if I had my spice rack. But despite this, I’ve never really considered what makes herbs TASTE so good. I mean, what makes basil that little bit tinny? Why is rosemary woody and how does thyme get that richness?  Parsley’s grassy notes, and the bitterness of sage-they must come from somewhere. And that somewhere must be a compound. Chemistry will have the answer, surely!

Flavour compounds are something that I knew about in that vague, loose, “I can BS about this for a bit but don’t really know what I’m talking about” kind of way. There are meant to be loads of them in wine, coffee and chocolate, which is why there are connoisseurs of those things, wine tasting events and aromatic blends sold for extortionate prices in delis. Not that I have a problem with that. In fact, I have recently discovered wine-tasting as a new and exciting hobby, so may well assault you with a post on that soon. I was also vaguely aware that esters are flavour compounds present in fruits like raspberries and pears, and give pear drops that nail-polish remover-esque pong. These flavour compounds are volatile, i.e. have a low boiling point, so they evaporate from food at room temperature, making them easily detectable by the olfactory system in the nose. This is why when you have a cold things don’t taste as good, because the compounds can’t reach your olfactory system as well due to your blocked nose. The sum total of my existing knowledge clearly wasn’t going to make a blog post. Cue a trip to my favourite search engine (no names, but they have an excellent doodle today).

It turns out that a lot of people study this kind of thing. I very nearly incorporated a job search in to my day to see if I can work for these marvellous people and spend my life working out why basil tastes like basil. Then I realised that if I did that and tried to tell people about it at grown-up dinner parties, they would think I was some sort of hippy who’d thought up my research question whilst stoned and eating cold lasagne. Plus people have already done that with EVERY TYPE OF BASIL there is and made a table of it. So it’s back to the heart disease. I’ll just have satisfy myself with telling you all what all those other people found out. So here goes.

We’ll start with the basil. Someone called James E. Simon and his colleagues have summarised the aroma compounds present in just about every variety of basil going in a paper available from here: http://www.hort.purdue.edu/newcrop/proceedings1999/v4-499.html. Whilst not in all of them, it appears that linalool is found in most varieties. This got me excited. Linalool was a compound I first encountered in my undergraduate lectures two and a half years ago and I think it’s pretty interesting. It is a monoterpene, which is a molecule made up of two isoprene units. The biological equivalent of isoprene is called isoprenyl pyrophosphate, and is a 5-carbon building block of many, many biological compounds, lots of which turn out to be flavour compounds. Linalool itself is found in coriander, lavender, tangerine, spearmint and chamomile, amongst many others. It is also related to limonene, which exists as two enantiomers (mirror images of each other), one of which has a distinctive orange smell, and one of which has a more turpentine-like smell. What is interesting about this is that both enantiomers are naturally occurring- a rare phenomenon in the world of chirality. The orangey smelling one is, usurprisingly, found in oranges, whereas the other enantiomer is metabolised to form menthol, amongst other compounds. Cool. (Disclaimer- when I say cool, I mean I think it’s cool. You are perfectly at liberty to disagree and/or roll your eyes and close your browser).

Terpenes are actually found in lots of herbs and seem to make excellent flavour compounds. They are generally quite small, having a molecular weight of less than 300, and are volatile. Terpenes found in herbs include camphor in rosemary, thujone in juniper, and myrcene in bay leaves. There are LOADS more of these compounds, many of which are found in other spices and plants used in cooking. I thought I liked them before, but now I’m a massive fan. They will probably find their way on to this blog again in the near future, so look out for that if you are as interested as me (probably not, but it’s worth a try).

But before I nominate terpenes as my favourite class of compounds (not that I would-that would be a bit much, wouldn’t it?), let’s have a look at which other compounds are responsible for yumminess. Thyme is my favourite herb- I feel like that’s an acceptable favourite to have- and yet nowhere can I see a terpene responsible for its flavour. That’s because the aroma compound in thyme is an aromatic compound named, rather imaginatively, thymol. But wait a minute! This is a cleverly both an aromatic compound AND a monoterpene phenolic compound. So terpenes do actually win the title of my favourite compounds ever. Lucky them. Thymol turns out to be closely related to apiole, which is a major aroma compound of parsley, estragole, found in tarragon, and the startlingly similar anethole, which is a component of anise and sweet basil. Aromatics are also found in almonds, cloves, cinnamon and vanilla, but as they aren’t herbs, they aren’t allowed more than a passing mention here.

There’s a lot more I could go into regarding flavour compounds and the like, but I’ve already rambled on enough for now, so will subject you to all that another day. Right now, as a reward for getting to the end of this with your sanity intact, I’d say that it is THYME for a nice cup of (herbal) tea. (That definitely deserves an eye roll.) Over and out.

Going Bananas

Yikes- it has been over a year since I last wrote anything on here, but recently, I was asked to write an article for my college magazine and (although Linacre Lines) had first publishing rights, I thought I'd whack it on here for those of you who don't have access to that high-brow and high impact publication.

We’re all used to a bit of geekery in Oxford. For most of us, reading around our subject isn't just a matter of making sure that our research sounds extremely relevant and important to a funding body, but an actual pleasure. Maybe I exaggerate, but I'm basically asking for your forgiveness and understanding as I get WAY too into a topic very tenuously linked to my subject for my own good. And for pretending that food can be an academic subject. Although I'm not the first person to have done that- there’s actually a guy who calls himself a Molecular Gastronomist. His name is Hervé This and he is really a physical chemist who likes to play with food. Sometimes he succeeds in making it dreadfully boring (“Algae contains fibres whose nutritional value is comparable to that of vegetable fibres.” Yawn!), but other times, he comes up trumps and gives some great tips on how to make a soufflé rise, or indulges me in my gluttony with pieces entitled “In Praise of Fats.” Amen to that! So I decided to take up his mantle and try to find and impart some (possibly a little bit) fun, scientific food facts, which satisfy the chemist in me and are mildly entertaining to most people who take an interest in what they put in their mouth.

For a good while now, I have been cataloguing a list of intriguing facts about bananas (I did ask for your forgiveness and understanding). This all started with the wonderful myth that an Oxford interview candidate was once asked to tell their interviewer about a banana. I sincerely doubt that this was the case, but began to ponder what on earth my response to such a question would be. I presume that in a Chemistry interview, some level of scientific detail would be required, so instead of describing majestic curvature and optimistic shades of yellow, I set about some taxonomy, inorganic chemistry and a touch of biochemistry.

My first revelation on my magical journey to understand this mystical fruit was that the banana ‘tree’ is actually… a herb. This nugget of knowledge was received with much scepticism by my friends (“Yeah, yeah Becky, next you’ll be telling me that a strawberry is actually a fish”) but a triumphant Google search- I didn’t say that this would be well researched!- revealed that I was, in fact, correct. The banana plant is of the herbaceous genus Musa, with the fruit we eat coming from the species Musa acuminata and Musa balbisiana. The herbaceousness of the banana is due to its trunk being comprised of leaves, rather than of woody matter. Who would have thought?  So, with those facts under my belt, maybe the Plant Sciences department would have me (possibly Classics, too, because of the Latin). But what about the Chemistry?

Doubtless many of you know that bananas are extremely rich in potassium. Possibly fewer of you know that this renders them a tad radioactive. An isotope (that is, a version of an element with the same number of protons but different number of neutrons) of potassium-40 (⁴⁰K) is radioactive, as it decays to calcium-40 via emission of an electron or to argon-40 via the emission of a gamma ray and a neutrino. Sounds quite scary, doesn’t it? But don’t worry, the amount of the radioactive potassium in each banana is very low, about 0.045mg, which equates to 0.1μSv radiation, so eating one a day isn’t going to cause you much damage. Some jokers at a U.S. think tank came up with the idea of the “Banana Equivalent Dose” to gauge the levels of radiation emitted by more strongly radioactive items. I’m not sure how useful it is to know that you absorb the same amount of radiation from a chest X-ray as you would from eating two hundred bananas, but I feel strangely reassured. Excellent. Chemistry covered.

Now, finally, the biochemistry. Have you ever seen those banana hooks? The ones you are meant to hang your bananas on instead of just chucking them into the bottom of the fruit bowl. Well, it turns out that they are not for purely aesthetic reasons, which is, I am sure, why people buy them. If this was an Art History interview and I were waxing lyrical about sunny hues and crooked forms, then I know that those hooks would be instrumental in my answer. As it is, they can also play a part in my scientific missive. Putting bananas in the fruit bowl is a bad idea. Fruits give off ethylene gas, which is a very simple organic molecule and a plant ripening hormone.  In the fruit bowl, the concentration of this gas in the atmosphere surrounding the fruit is high, causing the bananas and other fruit to ripen quickly and resulting in acute sadness when you find that your recently wonderfully yellow and firm fruit is now a squishy brown mess and devastatingly inedible. Unless that’s how you like your bananas, in which case throw them into the fruit bowl at your heart’s content.

So there we are. The next time you are being interviewed and the subject of bananas comes up, you too will be able to bore the pants off your prospective future employer and compromise your future to boot! 

Rise to the Challenge

It's been quite a while since I last wrote. I blame the end of term and Christmas. I had completely intended to write something over the Christmas period about, oooh, I don’t know, some funky chemicals in cranberries that make them a superfood, or the exact make-up of Brussels sprouts. But I failed miserably to do this, largely because I was at home eating vast quantities of the aforementioned (and other foods as well- it wasn’t some ridiculous diet effort!) and hanging out with my family. All very lovely, but not very productive, and now the moment for a festive post has pretty much passed. Maybe next year. Or actually, this year!

So this time, in a fit of New Year guilt, I will firstly make a resolution to pull my blogging socks up and write at least once a month, and then write a proper post, of decent length and appropriate content. Fortunately, yet again, I don’t have to look much further than my email inbox for inspiration. I was renewing my subscription to the RSC the other day and half wondering why I was doing it, as I am a terrible member and very rarely take advantage of the many benefits that could come my way if I was slightly more organised and had a little more time. The last six months’ copies of Chemistry World are sitting unloved and unread on my desk and I keep promising myself that I will read them instead of buying Glamour. However, whilst pondering this, an email popped into my inbox with the title “RSC Yorkshire Pudding on BBC Countryfile.” Bingo! £17 well spent.  Apparently, a few years back the RSC put out a press release detailing how high Yorkshires should be, along with a recipe for achieving the necessary 4 inches. Countryfile got hold of this and voila, a Sunday evening segment was born.  A quick hop onto iPlayer and I was disastrously disappointed. Aside from renaming the ingredients with ridiculous scientific terms (milk= lactose solution, eggs= protein ovoids) there was no science mentioned at all. Furthermore, the scientific recipe, whilst obtaining a great rise and good flavour, didn’t even win the challenge against a farmer’s wife’s traditional recipe. Maybe that £17 wasn’t worth it, after all.

The obvious thing to do next was to consult the great King of Molecular Gastronomy, Mr Hervé This himself. I had read his highly informative account of how to get a soufflé to rise (the answer is to use very firmly whipped egg whites to create a stable foam from which air finds it harder to escape, to seal the top of the soufflé by grilling slightly before cooking to prevent air being lost from the top, and to heat from the bottom by placing the dish on the floor of the oven, because hot air rises- simplicity itself, isn’t it?) so I wondered whether he would have a similar missive on the science of the humble Yorkshire pudding to allay my disappointment. Alas, no such luck. Still, I’m grateful for the soufflé tips!

Finally, I resorted to a Google search and triumphed. According to this website:

http://www.streetdirectory.com/food_editorials/pastry/baking_tips/science_of_a_yorkshire_pudding.html

the secret is all in the egg content. Eggs contain a large amount of protein, which forms a stable structure, allowing the Yorkshire to support its own weight. This is due to the unravelling of the protein strands in the egg, which then form bonds to other unravelled protein strands. Also, in order to achieve the rise in the first place, the mixture must be poured straight into really hot fat (carefully) which is almost smoking. This starts to cook the batter instantly and creates steam, which rises and takes the batter with it. Finally, the batter must be cooked enough to get a crispy outside, helping to prevent the pudding from collapsing when it is removed from the oven.

There you have it; the perfect Yorkshire pudding. Maybe someone should tell the RSC...

Short but sweet

This week’s post comes courtesy of an email from my Dad, so once more, I’m not really doing my own research and my life has been made easy by fortunate coincidence. My topic this time, by pure chance, is sugar.

So, what on earth has sugar got to do with science, I hear you ask. Good question. Well, actually, you were probably all made to learn the structure of glucose (C₆H₁₂O₆ etc.) and all that aerobic respiration and photosynthesis business, which is all very well and quite interesting if you’re into that kind of thing. But you can all look up your notes on that, if it so takes your fancy, or Google it if you really want to know.  I’m more interested in a particularly novel and different use of sugar by an environmental consultancy firm.

My Dad works in the building industry and somehow stumbled against this very interesting and unusual use of sugar in dealing with contamination of a site with hexavalent chromium and chlorinated aliphatic hydrocarbons. Hexavalent chromium (Cr(VI)) is chromium metal in the +6 oxidation state and is known to be a carcinogen, particularly affecting the lungs via inhalation. It’s also a pretty nasty irritant affecting the skin and internal organs if ingested. The sulphate system takes Cr(VI) into cells, where it is reduced to Cr(III) (Chromium in the +3 oxidation state) and then it is thought that some nasty radical chemistry occurs to damage the cell, leading to cancer and other horrible illnesses.  So we don’t really want it in the ground, or anywhere near us, thank you very much. Chlorinated aliphatic hydrocarbons, such as 1,2 dichloroethane, are also carcinogenic and again, definitely not wanted.

But how to get rid of these things in a safe and effective manner? Call in the chemists! The company concerned, RSK, (website found here: www.rsk.co.uk) decided to go for a large-scale injection of molasses into the affected area. Molasses is a by-product of the sugar refining process and is used in cattle feed, or, if from cane sugar, can be used in baking. Molasses from sugar beet contains sucrose, glucose and fructose. Bacteria use these sugars as a substrate for aerobic respiration, depleting the oxygen levels in the soil. This creates a highly reducing environment and the Cr(VI) is reduced to Cr(III) which precipitates as the hydroxide Cr(OH)₃ and can be filtered out of the groundwater. Easy! The reducing environment is also helpful in tackling the chlorinated aliphatic hydrocarbons, as they are reduced step-wise to ethane, ethene, and CO₂ and water. These gases diffuse out of the groundwater and are pretty much harmless. Some clever and careful planning was required to get the conditions just right for the degradation of the chlorinated aliphatic hydrocarbons but the process required no complex chemicals and was definitely economically viable. I was really impressed with the use of something that can be found in my store cupboard at home to tackle a real, scientific problem. You could call it sweet success!