An appropriate food, then, to match the hair-shirt mentality which descends after the Christmas excesses. And perhaps a suitable item to feed into a new, improved diet for the New Year.
The white, wobbly blocks of soy bean curd are beloved of the Chinese, the Japanese (who know it as tofu), the Koreans and, increasingly, health- food devotees in the West.
It is made from the soy bean, the most PC of all foods. Every analyst can quote you the statistics: a field devoted to the cultivation of soy beans produces 30 times more protein than one given over to feeding cows.
Among the pulses (peas, beans and lentils), the soy bean stands supreme; though it contains a mere third of the starch (carbohydrate) of most pulses, it offers twice as much protein (the body's building-blocks). Usefully, it contains 10 times as much oil as other pulses, this being the unsaturated, heart-friendly sort.
The soy bean is one of the most versatile food sources known to man (and a $2bn business in the US alone). Yet surely it is one of the dullest. A square of bean curd looks about as appetising as an uncooked loaf of bread.
The Chinese, the Japanese and the Koreans would disagree. Soy beans have been cultivated in China for at least 5,000 years, and have been pivotal to the survival of the Chinese.
This bean was chiefly considered a food of the poor, but was of immense value to the peasant subsisting on inadequate amounts of rice and very little animal protein. Around 960AD, Chinese writers made the first refer- ences to processed beans, or bean curd, made by pressing the beans and then curdling the resulting milky juices to make a wobbly junket. They likened it to "tenderly cooked lamb" and since then it has become something of a soul food to the Chinese.
And not only to the peasants. At the tables of the emperors, the court chefs exercised remarkable culinary dexterity in modelling bean curd into the shapes of fishes and small birds and even colouring them realistically.
In Japan, with its vegetarian Buddhist traditions, tofu is eaten by most people, along with miso, the fermented salty brown bean paste, and its universal by-product, soy sauce.
Although no part of our food tradition, the use of bean curd is increasing in the UK, though it has yet to take the supermarkets by storm.
London has a large Chinese community whose local stores take in fresh curd every few days - it has a shelf-life similar to that of dairy products. I've just been to see a small factory called Shanghai in London's Park Royal trading estate. It is the second largest supplier in the UK.
"We call it Shanghai because that was where bean curd was first traded for money, 400 years ago," says Richard Koh, the managing director.
Half a dozen people work here in a clean, dairy-like space, the floors running with creamy water, the air full of humid steam. The small brown soy beans, imported from Canada, are soaked for 18 hours. They are ground in a revolving press which spurts out a stream of white "milk". This is steam-heated to near boiling point for 10 minutes, then decanted into buckets with a coagulating agent to separate the curd from the "whey" (modern processing uses gypsum or calcium sulphate).
"Some of my customers are surprised," says Richard. "One of them told me that his father built his house using gypsum." Two parts of calcium per million remain in the curd, and even this minuscule presence is beneficial, for the formation and repair of bones.
The son of a Malaysian rice importer, Richard opened a Malaysian restaurant in Kilburn in 1988 and then, on the advice of his entrepreneurial bank manager (an Irishman, as it happens) went into bean curd. The bank manager passed him an American market report which promised it was the food of the future. Well, the jury's still out on that, but Richard made a go of it, recruiting Jimmy Mann as his partner, former maitre d' of the Oriental at the Dorchester Hotel (the only Michelin starred Chinese restaurant in the UK).
Jimmy Mann and Richard Koh eat bean curd about twice a week. Unlike the Japanese, they never eat it raw, and certainly not as the Koreans do, waiting until it gets over-ripe (like a cheese), and deep-frying it to kill the bacilli that develop on its surface.
Richard prefers it steamed, as does his son Rico, who can't get enough of it. Jimmy's wife Irene simmers it in vegetable soups, or deep-fries it (for three or four minutes) before adding it to stir-fries of broccoli and the like. Soy sauce, sesame oil and finely sliced ginger are the usual accompanying flavours.
Jimmy's favourite family bean curd dish is raw curd mashed with finely minced raw chicken (it can be pork or fish) and chopped spring onions. This mixture is then shaped into flat cakes or balls and steamed for 10 minutes.
Richard and Jimmy took me out and treated me to a delicious dim sum lunch at the Dragon City restaurant, located in London's biggest and newest Chinese supermarket, Loon Fung, around the corner from them.
One of the dim sum, a little steamed cake with shreds of pork finished in oil to give it a nice colour, turns out to be made with bean curd. It was undemanding food, very delicate and easy to eat, though I did prefer the other dim sum that contained something tasty to get your teeth into. But later, I experimented with bean curd at home and began to appreciate its silky properties.
Richard and Jimmy sell their curd to hundreds of Chinese outlets, restaurants and superstores, and export it to the Benelux countries and France. But how, they wonder, can they reach a greater British public?
This sounds like a mission for the great Ken Hom, the ubiquitous Chinese cook. Here, then, is one of his own and his mother's favourite recipes, although not one for vegetarians. Why not try it? It's very good indeed. It is the universal family dish in China, he says, where it's known as Ma Po's bean curd, and typical in that it stretches scarce meat to make a tasty, economical and nutritious dish. The range of spices used transforms the fresh but rather bland bean curd. The recipe is published in Ken Hom's Illustrated Chinese Cooker (BBC, pounds 15.99).
BRAISED PORK WITH BEAN CURD
450g/1lb firm fresh bean curd
112 tablespoons peanut oil
1 tablespoon finely chopped garlic
1 tablespoon finely chopped fresh ginger
350g/12oz minced pork
3 tablespoons finely chopped spring onions
1 tablespoon chilli bean sauce or chilli powder
1 teaspoon sugar
112 tablespoons Shaoxing rice wine or dry sherry
1 tablespoon dark soy sauce
1 tablespoon light soy sauce
112 tablespoons whole yellow bean sauce (if available)
1 teaspoon whole Sechuan peppercorns, roasted and freshly ground (optional)
65ml/212fl oz chicken stock
2 tablespoons finely chopped spring onions to garnish
Cut the bean curd into 1cm (12in) cubes and put them into a sieve to drain. Lay them on kitchen paper to drain for another 10 minutes.
Heat a wok or large frying pan until it is very hot. Add the oil and when it is very hot and slightly smoking, add the garlic and ginger. A few seconds later add the minced pork and stir-fry it for two minutes.
Add all the other ingredients except the bean curd. Bring the mixture to the boil, then turn the heat down low. Add the bean curd and mix it in well but gently, taking care not to break the chunks. Let the mixture simmer, uncovered, for about 15 minutes (if necessary add a little more stock). Garnish with the chopped spring onions. Serve with noodles or plain boiled rice.