一剑指北

The joy of soy

The controversial history of the soybean – and the uncertain future of tofu

Food studies is a subject so much in its infancy that it would be foolish to try to define it or in any way circumscribe it, because the topic, discipline or method you rule out today might be tomorrow’s big thing. The inadequacy of our conventional conceptual framework for dealing with this unwieldy child is bathetically shown on the copyright page of The World of Soy, where the “Library of Congress Cataloging-in-Publication Data” lists the volume’s subject matter as “1. Soyfoods. 2. Cookery (Soybeans). 3. Food habits”. Thus do our categories of taxonomy reduce the current state of our knowledge about the world’s fourth most important food, measured in terms of calories, and first among legumes. Measured in cash terms, soy (Glycine max) is in some ways the most important crop, and in terms of imports and exports, second only to wheat. The fact that this important book has contributions by seventeen authors reflects more than the circumstances of its origins in a couple of academic conferences; it also shows the vastness of the topic and the large number of disciplines required to make sense of it. Dealing with soy comprehensively requires the attentions of historians, nutritionists, sociologists, anthropologists, economists and specialists in agriculture, plant genetics – and cooks, for if we do not know how soy has been and can be used as human food, and why people would wish to eat it, we lack any fundamental knowledge of it.

Though it was domesticated more than 3,000 years ago, as the editors say in their introduction, “hardly any other food plant is as modern as the soybean”. They might have added, “or as controversial”. For, as press coverage has revealed, the clearing both of the rainforests and cerrados (savannas) of Brazil to grow soy, and the building of dams that are supposedly designed to help in its cultivation, are having dramatic effects on the survival of indigenous peoples and on climate change and biodiversity. There is an important distinction, though, to be made at the outset, between soy as food and soy as feed. In Brazil, some call chicken “soybeans with wings” and, as Sidney Mintz and Christine M. Du Bois, co-editors of this book, point out in their concluding essay, “of the world’s 2004 soybean production, some 93 per cent of the protein was processed into animal feed rather than human food”. But this cycling of soy via animals “is a spectacularly inefficient means of providing human populations with protein no matter how profitable it may be to the producers”. They instance the pig, where less than half the feed ends up as pork – the remainder ends up as the waste products of porcine metabolism, to put it politely.

It is an odd fact that this crop on which human nourishment is so dependent directly or indirectly, cannot be used by us as unprocessed food, except for the rarefied Japanese restaurant treat of edamame – green, immature beans in the pod. The soybean has evolved a number of chemical protections from pests, which range from being annoying to fairly toxic, which (to simplify) is why we cannot eat it raw; and when roasted or cooked in high, dry heat, the proteins form an indigestible tangle of compounds. There are other drawbacks to soy as regular human food: its flavour (which old Chinese sources disparage as “beany” – a consequence of oxidation of polyunsaturated oils by lipoxidase), and the fact that, like other legumes, its carbohydrate components (raffinose and stachyose) cause flatulence. But it was an invaluable crop in China because it could flourish in poor soil, is a nitrogen-fixing plant (which therefore does not further degrade poor soil), and, says Mintz, “was a vital fallback food in times of famine”. Somehow or other, the Chinese discovered that soy is made edible by fermentation – as are many other foods, and not just those of plant origin. In his own brilliant essay, “Fermented Beans and Western Taste”, Mintz cites Geoffrey Campbell-Platt’s surprising point that “something like one-third of all the food eaten on earth today has been treated by some kind of fermentation”, from meat and fish to dairy products and wine, beer and spirits. Though it is hard to document the use of fermentation before the development of agriculture and the domestication of animals, there is some speculation that its use as a means of preserving food (along with older techniques such as drying and salting) may have marked our ancestors’ transition from hunter-gatherers to sedentary agriculturists.

Mintz’s elegantly written contribution is crucial to the enterprise here, and shows why the concrete, particular knowledge of food from a cook’s (or at least, a curious eater’s) perspective needs to be incorporated into food studies generally. It is essential at the outset to notice that, while Western diets include a good deal of fermented dairy produce, especially cheese – of which we have a staggeringly large variety – pickled fish, meats and vegetables, and cereals (just think of the hundred-plus single malt Scotch whisky brands, and thousands of beers and wines), “the lack of fermented legumes in Western culinary traditions seems slightly puzzling at least”.

Eastern culinary cultures also make use of fermented cereals, vegetables and foods of animal origin. Fermented legumes may seem simply to be a bonus, until we explore exactly what they are, and begin to realize that they are central to the cuisines in which they feature. The most important products are soy sauce in China, Japan, Korea and, to a lesser extent, in South-East Asia; the soup flavouring miso and natto in Japan; tempe (or tempeh), the Indonesian main course ingredient, a cake made from boiled soybeans, and the related oncom, which can be made from pressed peanuts as well as from soy pulp; and the soybean paste jiang (or chiang), important not just in China but under its local names in Korea, Indonesia and the Philippines. Soy sauce is the principal flavouring in most of the cuisines in which it features; one cannot imagine the food of China, Japan or Korea without it.

However, there is one soy product even more important worldwide, and that is bean curd, tofu (doufou). Besides processing soy by fermentation, the Chinese also discovered the technique of sprouting the beans, though soybean sprouts did not became popular until the Song dynasty (960–1279). The third Chinese processing technique was grinding the beans (following the discovery of the stone rotary mill in the Warring States period, 480–221 bc). Mixed with water, the milled flakes produced a milky emulsion, soymilk, though this still has the digestive disadvantages of the raw bean (and it was not until the eighteenth or nineteenth centuries that it was learnt that prolonged heating of the milk rendered it easily digestible). Tofu is made much like cheese, in that a coagulant (now usually gypsum) is introduced into the soymilk, producing a custard consistency, which is then drained to produce curd. The difference, as we learn from the essay by the third editor, Chee-Beng Tan, is that the entire “process of making tofu from grinding beans to pressing takes only an hour”. Though a labour-intensive process, it is a major, cheap source of protein. Tan quotes a recent study showing that the soybean “yields more usable protein per acre than other common cultivated plants”, and, of course, it is strikingly more efficient to turn soy directly into protein for human food than to do so indirectly by feeding it to livestock. An interesting form of cooperation grew up around the making of tofu in some of China’s poor rural villages, where every family knew how to make bean curd. When one household produced tofu, the others would either borrow some, to be paid back when it was their turn to make it, or give a quantity of soybeans in exchange for the processed tofu.

Soy is also the world’s most important oilseed crop. The burning issue with soy, as with so many other crops, is the acceptability of genetic engineering. Genetic modification holds out the promise of removing soy’s disadvantages – of doing away with its disagreeable flavour, its flatus-producing properties, its instability problems, nutritional deficiencies in its amino acid profile (though not as good as meat or eggs, it is much better than most plant foods), and of remedying its vulnerability to disease, insect attack or competition from weeds. In the chapter on genetic modification, Du Bois and Ivan Sergio Freire de Sousa summarize the reactions of “control, dread, outrage” raised by Marion Nestle’s work versus the “promise, hope and choice” held out by Per Pinstrup-Andersen and Ebbe Schiøler: “Because the stakes are high, the issues complex, and the stakeholders so numerous and varied, it seems prudent” to proceed, but with caution. This fence-straddling position, however, is preceded by some paragraphs of scepticism (which I share) as to whether GM soy can ever be of benefit to the poorest farmers.

Most of this volume, indeed all but the first four pieces, consists of discussions of the role of soy foods in – apart from the United States – cultures in the non-English-speaking world. Though the US was, until 2006 (when a statistical tie with Brazil developed), the world’s biggest exporter of whole soybeans, it uses most of its own consumption as feed, not food – with the exception that soy oil is now the most important edible fat used in American kitchens. So, for instance, there is a chapter on tofu as a celebratory food in Sichuan (the province that gave us the best-known and most delicious of all bean curd dishes, the fiery ma po doufu, “pock-marked woman’s bean curd”, made with minced pork and plenty of chilli). An appendix to this contains the only poorly edited part of the book, three useless “Contemporary Innovative Tofu Recipes”, which give no quantities at all.

Among the outstanding contributions to this volume (which is part of the University of Illinois Press’s excellent Food Series) is Erino Ozeki’s “Fermented Soybean Products and Japanese Standard Taste”, an anthropologist’s approach to cultural differences in taste preferences. She gives a model of the Japanese “pattern of flavours repeated in many dishes” that represents “the favourite taste of that cuisine”. It is probably a little easier to specify the elements of this pattern for the Japanese “standard taste” because there are only two – the fish stock called dashi, an infusion of dried fish and seaweed, and fermented soy products, namely soy sauce and miso – than it would be for the less uniform French, Italian or, come to it, British taste. This approach could be very fruitful in exploring the differences between similar cultures – the American flavour pattern will have a sweet foundation that is not so apparent, for example, in British taste preferences. Weirdly enough, though, the ultimate question of “Soy’s Dominance and Destiny” (the title of the concluding chapter) really boils down to whether the populations of South America, East Asia and West Africa can learn to love tofu. I’m not optimistic; but this exemplary, comprehensive volume shows the way to frame the crucial questions of food studies.



THE WORLD OF SOY
337pp. University of Illinois Press. ; distributed in the UK by Combined Academic Publishers.

[ 本帖最后由 一剑指北 于 2009-3-22 19:38 编辑 ]