Reading progress update: Part 1 - The Sustaining Science of Food and Drink

The Science of Everyday Life - Marty Jopson

A long overdue update on the buddy read with Murder by Death of Marty Jopson's Science of Everyday Life:


I'm not sure about this book, yet. The first part  - and, looking ahead, the other parts, too - is made of short sections on different topics in the general theme of Food and Drink, some more interesting (even if somewhat revolting - see Prawn Crackers update) than others. I enjoyed the explanation of why egg whites change colour when heated, I also enjoyed the prawn crackers story, and the description of why onions make people cry. 


I was decidedly less interested in the parts about bread and baking, except that the discussion of the tax implications with respect to cakes and biscuits had me research the UK VAT (value added tax) rules for longer than I ever thought I would - and it was bizarrely fascinating.


The distinctions between taxable and tax exempt may all seem arbitrary and mad, but at least there is a clear acknowledgement that cakes and biscuits are necessities in life and therefore exempt from tax.


With respect to the onion section, Jopson tries to describe why it is that onions make some people cry. I added "some" in this as Jopson doesn't actually go into why onions affect some people but not others. I've not been affected by onions when cutting them in ... decades, so his generalisation made me think about what other generalisations he may have mixed into the "science parts".

Take a knife and start to slice up the flesh of an onion. As you do this, you break open lots of the unusually large cells of the onion. Within these cells are two chemicals that normally don’t come into contact, since they are contained in different cellular compartments. By cutting open the cells you also break these compartments and the chemicals mix. The first of these substances is a group of protein-building blocks called amino acids, linked to a sulphur and oxygen atom. When these sulphur-linked amino acids encounter an enzyme known as alliinase, they produce a highly reactive sulphenic acid. (And I have spelt the word alliinase correctly. It comes from allium, the scientific name for the onion genus of plants, and for reasons unknown the enzyme has an extra ‘i’ thrown in for good measure.) The creation of the sulphenic acid is not the end of the chemistry; a second enzyme gets involved. The grandly named lachrymatory factor synthase gets to work on the sulphenic acid and produces – you guessed it – lachrymatory factor, or syn-propanethial-S-oxide – I think it would be wise to stick with lachrymatory factor in this instance. Now we are getting to the tearful end of the story, as lachrymatory factor is a highly volatile liquid that turns into a gas that floats up to your eyes. It’s possibly surprising that the see-through part of the front of your eye, the cornea, is packed with sensory nerve endings. These are there to detect anything that touches the delicate cornea, and when this happens we unconsciously blink and also produce tears to flush the irritant away. The lachrymatory factor sticks to these nerve endings, fooling them into believing that something hot has touched our cornea. We feel this as a burning pain, even though there is no heat there, and we begin to cry, or to lachrymate, to use the fancy word. There are many chemicals that can cause the same reaction – capsaicin, for example (see here), but it is only onions and their relatives that produce a gas that does this.


Anyway, the onion section reminded me that I have this:



They were a Secret Santa thing, I think, as otherwise I have no idea how I got them... No idea if they work.