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!