Friday 9 December 2016

Mon pet du chou

Forty years ago as students we had a copy of John Seymour's Self-Sufficiency and aspirations about making food from scratch. It was more normal then before everyone out-sourced so much food-preparation to a factory in another county whence it came to a local shop in a neat box with cooking instructions [multiprevlier]. In the fall for several years I would make a vegetable chutney, sometimes in absurdly large glass jars, which was never anything like, or as good as, Branston Pickle [R next to an enhanced cheese sandwich]. My pickle required boiling up a lot of chopped veg with vinegar and then putting it in jars for as long as it remained un-furry. It was actually on the verge of repellent and I only ate the stuff out of a sense of duty to my craft. I hadn't a clue. I was learning it all from books because I was a long way from home, and even home was along way from traditional kitchen practice.

The final section [earliers] of Michael Pollan's Cooked is, not very well, entitled Earth and is about pickles and ferments. It turns out that I was mad to be buying vinegar and salt as way of lowering the pH and raising the ion concentration of the vegetables so that they would not seem tasty to 'bad' microbes. I should just, like a master of Aikido, have tilted the tables so that some microbes would make their own acetic and lactic acids as a by-product of partial digestion of the veggies and thus deter other microbes from getting in on the act. I've learned a lot more about LABs Lactic Acid Bacteria since I had to teach it at the Institute than I ever learned in school or poring over cook-books and Self-Sufficiency. LABs are a key component in the transformation of cheese, yoghurt, buttermilk and sauerkraut,

But, according to Pollan, the LABs are only a stage in the process of ecological succession that converts the sulphurous fibre of cabbage into crunchy and digestible sauerkraut and kimchi. The first step appears to be carried out by Enterics, from the gamma proteobacteria that also include E.coli, Salmonella, Vibrio cholerae, Enterics, despite their name, normally comprise only about 1% of the intestinal flora and we quietly ignore them until we eat out at a sketchy burger joint and spend the next two days talking on the porcelain telephone. As the enterics fade in their vigour, poisoned by the own waste, then Leuconostoc mesenteroides steps up to the plate to clean up the mess. They are the weeds of the microbial world: fast growing, adaptable and tolerant. As they convert the available sugars into lactic and acetic acid, first bubbles and then a positive fizzzz of carbon dioxide starts to emerge from the seething surface. When Leuconostoc has made life intolerable for itself and its children, then Lactobacillus planatrum presents itself as having even lower standards and starts to divide and conquer. You don't need to know this history of transformation, you can just leave things to happen in their own sweet way and wait until the bubbling and burping stops.

If you open the lid too soon you may encounter evidence of a transient member of the community, as sulphate reducing bacteria start to pump out hydrogen sulphide and your brew starts to smell distinctly funky: old egg sandwich in spades. But there is only a little sulphur in cabbage and the farty-effects only endure for a little while. As with presents coming up to Christmas, it is best not to peek into the sauerkraut vat too early. Interestingly the biochemical tool-kit for reducing sulphur can be carried by two wildly different groups of bacteria: 1) the delta proteobacteria like Desulphobacter and Desulphobacula and 2) gram positives like a Desulfotomaculum and Desulfosporomusa. These microbiologist desulpho-namers of bacteria seem to lack for desulpo-imagination.  Remind me next September to offer a research project comparing the sulphur-metabolism genes of these two very different groups: bet you there is horizontal gene transfer going on.

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