Derby British Science Association

Science and Engineering in Derby and Derbyshire

Kitchen Chemistry

Lots of people think of science as being this big thing that happens in sinister looking buildings filled with machines with names that sound like something Gene Rodenberry rejected for sounding too nuts. Science, according to television, is done by stern looking people with thick rimmed glasses and more letters after their names than in them, or remarkably glamorous looking sex-kittens who swish their hair every so often lest you forget that they are not only an amazing scientist, but also a girl. Whilst there is plenty of science going on in big buildings, they’re not generally very sinister (unless post-war concrete gives you the heebeejeebies), the scientists do more filling in forms than rushing excitedly down corridors, and CSI et al seem to miss out all the parts where the scientists stare at their madly named machine willing it to work just a little bit faster so they can go for a fag. BUT…you don’t need all this to do science (unless you want to do some genome sequencing then we certainly recommend the big sinister building with lots of lab-coated minions and fancy machines)…You’ve been doing science all your life, and the first place you probably started is the kitchen…

Consider my toasted sandwich here…

Consider that it’s my sandwich first and foremost, but then consider the amount of science that went into getting it to my plate…
Starting with the contents…
I don’t eat cheese made of milk, so my toasted cheese sandwich is technically a toasted pea protein sandwich, but that sounds considerably less appealing. This is big building science at work here, you could do this at home but since it requires soaking your peas, soaking again, watering and then spinning them around so fast that they come all to pieces you probably don’t want to. An awful lot of mushing and pressing, and often the addition of proteins from soya beans too, and you have faux cheese. Of course one of the most scientific things in the consideration of faux cheese is pondering how the devil someone decided peas would make good cheese…

Real cheese starts the process in a way that many people will be familiar with, making curds and whey. For DIY cheesemakers you might do this with vinegar, or lemon, but industry typically uses bacteria to do this. One of the common bacteria groups used is Lactobacillus, which you might recognise as one of the bacteria in gut flora, and countless strange little drinks and yogurts. Lactobacillus is pretty common in the squishier parts of humans such as the intestines and vagina. Though you’ll be pleased to know though that humans are not the source for cheese production! Lactobacillus converts lactose (a sugar in milk) to Lactic Acid. As well as the bacteria, most cheese, particularly harder cheeses, also contain rennet to help this process along. Rennet is an aid to digestion which occurs naturally in mammal stomachs and separates the milk, much like the acid or bacteria does. It contains a cocktail of enzymes, with the main one being chymosin, which make it excellent at its job. Though traditionalist cheesemakers might still use calf rennet, most cheese in supermarkets (~90%) uses something called Fermentation-Produced Chymosin. This makes use of the power of cloning technology to have yeast producing Chymosin B during the fermentation stage, making the cheese suitable for those who follower Kosher, Halal and vegetarian diets.Then before it makes it to the supermarket the cheese has a few salty baths and some squashing to look forward to.

The next part of my sandwich is Harissa (Tunisian chilli sauce). Its primary ingredients are members of the Capscicum genus, often serrano, and pilli pilli. The Capsicum group of plants are a varied bunch ranging from the very mild bell pepper that adorns lunchtime salads up and down the nation, to the mouth blowing Trinidad Scorpion Moruga Blend, which is the hottest pepper on the planet. Peppers are a member of the diverse Solanaceae plant family. This family includes the innocuous potato, aubergine and tomato, the unhealthy but popular tobacco, and the very toxic Deadly Nightshade. peppers get their spiciness from 8-Methyl-N-vanillyl-trans-6-nonenamide, or capsaicin, which is produced by the plants as a secondary metabolite defensive system. They are hot to try and stop you munching their fruit. Unless you happen to be a bird, on whose beaks capsaicin has no effect. The spiciest bit of the pepper is not the seeds, they don’t contain any capsaicin, but the bit where the seeds attach. There is no shame in surgical gloves when cutting chillies. The reason the peppers are irritants to mammals but not birds is because of the catchily named transient receptor potential cation channel subfamily V member 1, or TRPV1, which detects and regulates body temperature. As part of this job it is responsible for causing burning pains, which are particularly useful when you’ve actually burned yourself. However, capsaicin binds to TRPV1 which leads to the sensation of your mouth being on fire when you bite down on a chilli. That spiciness is measured by the Scoville Scale. The original method of establishing the hotness was rather like dinner party homoeopathy.  The peppers would be dried and have oil extracted, this would be gradually diluted down until a tasting panel could no longer detect the spiciness. The number of dilutions would dictate the Scoville rating. These days most peppers are analysed with chromatography to give a pungency rating, and then this number is translated into Scoville numbers for pepper fans. American police pepper spray and the Trinidad Scorpion Moruga Blend come in at somewhere between 1.5 and 2 million Scovilles, mild Scotch Bonnets are around 100,000, which is the same as pure piperine-the spicy quality in black pepper, jalapeños are around about 5,000 and salad peppers rate at zero as they lack capsaicin.

Margarine stops my pretend cheese and not so pretend chilli peppers from seeping through the bread acting as a barrier. Invented by the wonderfully named chemist Hippolyte Mège-Mouriès, margarine was patented in 1869 and was one of the products upon which the Dutch end of the Anglo-Dutch giant Unilever built a fortune. Margarine is an emulsion, which means that it is a mixture of two liquids that are normally non mixable. Emulsions, and colliods (which is where one substance is dispersed in the other but is not dissolved, and they don’t bond) are essential in the kitchen. They aren’t just things that are produced by manufacture-milk is a colloid with fat drops dispersed in the liquid part. The components of margarine and other emulsions such as Hollandaise Sauce generally stay together thanks to emulsifiers. In industrially manufactured products this is often lecithin, which keen chocolate consumers might recognise from the back of their milk chocolate. Soya lecithin is a common ingredient in milk chocolate as that is yet another colloid. It isn’t just in industrially made foods that emulsifiers play a role, home made chocolate mousse, and countless salad dressings, use egg as an emulsifier.

Then we move onto the bread. Bread and cakes are some of the most accessible bits of science available. Anyone who has ever attempted to bake without some of the essential ingredients, or used gone off yeast (guilty m’lud) will know that baking doesn’t work like other cooking. When it comes to stir-fry you can randomly bung things in and still end up with something pretty edible. You can sub arborio in your risotto with pudding rice (dry rice, not rice pudding that is!) and still have perfectly nice dinner. But bread and cakes are unforgiving. Deviating from the bread recipe is not for the faint-hearted, or those prone to lying on the floor weeping when what comes out of the oven resembles more house brick than brioche. When they say measure they mean it.

Yeast doing its thang after ten minutes in 110 degree water

In bread one of the hardest things to balance, especially if you are going off-piste for the first time, is yeast. Yeast is essential in ‘normal’ bread to help it rise, but they are delicate little chaps. Put it in the mix with water too cold, and nothing happens, too hot and you scald it. And even worse unless you are making the yeast up separately you won’t even know how much this has failed until after the rising time…Breadmaking demands a thick skin. And science. Saccharomyces cerevisiae is the yeast used in baking (and brewing) and it converts carbohydrates to carbon dioxide during fermentation. Which is hopefully what it is doing in the rising phase. However, it isn’t just the yeast that is responsible for your bread rising. Flour contains the proteins glutenin and gliadin, and when you knead your bread the two collide and link together. All of the linking together makes something rather like a coat for the dough which traps air, produced by the yeast fermenting inside. The coat is more commonly known as gluten, and this is one of the reasons that some of the gluten-free breads look a little on the heavy side.

Cakes also make use of gluten, though obviously you don’t generally knead cakes, so this is generally developed through all that vigorous beating. The flour that you use in cakes (assuming you don’t use bread flour) is generally made from wheat that produces less gluten. Cakes need some, but not as much as bread. This is because modern cakes have generally two methods of introducing some rising powers. In most cake recipes the fundamental ingredient is the eggs. Depending on what type of cake you are making will dictate what type of role the egg is playing. In fancy meringue type cakes, such as the Sachertorte, the egg is serving as a binder, emulsifier and raising agent. In the typical victoria sponge they serve for their raising properties. The beating of your eggs, or in some cases just egg whites, forms something called a foam. The foam as it develops traps gasses in it. Generally recipes will tell you to beat the eggs, and then add them to your other ingredients in relatively quick succession. Though the proteins that cause the foam are relatively stable, compared say with milk foams which will go limp in mere moments, you don’t want to be leaving them around for ages before you mix the egg into your cake. What though keeps your cake up if, like me, you don’t eat eggs? In most cake recipes eggs are not left to do all the rising work by themselves. Baking powder or bicarbonate of soda are typically added, along with salt, to increase the cake’s ability to rise. Bicarbonate of soda is simply that, but baking powders are a mixture of different leavening agents. Baking powder will certainly contain bicarbonate of soda, but the other ingredients will depend on the manufacturer, how much it cost and where in the world you got it from. Monocalcium phosphate, and Sodium aluminium sulphate are commonly used. Baking powder works by having a reaction party all by itself. Bicarbonate of soda is an alkaline, and the other ingredients are acids which once you start mixing them around in your bowl react with one another to leaven the mixture. If you are using bicarbonate alone you need to have something in the recipe for it to react with, so if you are making something with buttermilk or fruit juice in it is ideal. In some recipes it might seem like the soda has nothing to react with, but acids are in places you might not expect. Cocoa powder which has not been Dutch processed is an acid. However, whilst natural cocoa powder is readily available in the USA and South America most European cocoa has been Dutched. So if you have a taste for American cupcakes and they look a little limp you might want to try swapping for baking powder, or add in cream of tartar which is an acid for the soda to react with. If you are skipping eggs from a recipe that lists them make sure you compensate with other leavening things to create enough of a reaction, so add both baking powder and soda, and another acid such as acetic acid-be prepared to do what all good scientists do, repeated experiments (and eat your failures).

So even if you didn’t realise it you’ve been doing science for most of your life. You don’t need pipettes nor fancy flasks…none of that (although some of us have those things in our kitchens, but we ask you not to judge us…)
The kitchen is a great place to introduce children to science too. As long as they don’t eat you out of house and home, and are supervised (especially with non-edible items) it’s a great place to learn more about everything from chemical reactions to why ovens work. There’s also plenty of cheap non-cooking experiments that you can do, and the Derby branch is holding a free workshop next Tuesday lunchtime of some simple experiments with kitchen items that parents and carers can do with children. It will be at Derby central library in town drop in anytime between half twelve and half one.

About Lotte

Likes making a mess and arguing.

2 comments on “Kitchen Chemistry

  1. mydearbakes
    November 10, 2012

    Yum! What a fabulous looking bake! =D

  2. Lotte
    November 11, 2012

    Reblogged this on Ou ma colère va and commented:

    I wrote this for the Derby Science Blog but it sort of fits here too since I like talking about food around these parts…

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This entry was posted on November 9, 2012 by in Activities and Events in Derby, Branch Events, Chemistry and tagged , , , , , .

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