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.