Jeff & Linda's Kitchen of Diversity
The Miracle of Soy
Up until now, we have focused the blog on ethnic vegetarian cuisines and how these are intimately linked to the physical and ecological environment and human history of their respective regions. This month we're going to take a different tack. As mentioned in our introductory blog entry, in an effort to keep the industrial-agricultural complex as far away from our kitchen as possible, we are also passionate about making as much of our own foodstuffs as we can. Our food interests thus have a strong Do It Yourself streak, whether it be making our own stocks or sausage, baking our own bread, fermenting our own sauerkraut, or putting up as much of our garden's harvest as possible as various canned goods. Given the prominence that tofu and miso played in last month's Japanese recipes, we're going to focus this month on a set of DIY projects related to making these and other soyfoods in your own kitchen.
The soybean (Glycine max) is the most recently domesticated of our major legume crops, dating back only 3100 years ago to northeastern China and Manchuria. This crop contains some of the highest protein levels for any vegetable (about 35% by weight) and produces 20 times more protein per acre than the amount of animal products generated by the same area of forage. It is thus not surprising that by 2000 years ago in mainland China and 1000 years ago in Japan, soy had become one of the dominant protein sources.
There is a major problem with eating soy, however: first, it is especially difficult for the human stomach to digest, and is well known to be among the most gas-generating legumes due to high levels of oligosaccharides. Jeff is particularly sensitive to this aspect of soy, and can vividly remember being incapacitated and rolling around on the floor with severe stomach cramps for at least two hours from eating only a handful of dry honey-roasted soybeans. It is not something that he ever plans on doing again. Second, soy also contains a compound which restricts the activity of the trypsin enzyme in digesting proteins. As a result the high protein levels in soy are not available to us and will simply pass through our gut unless 80% or more of this compound is broken down.
Even though the use of cooked soybeans was commonplace in US vegetarian cooking up through the mid-1970s, these two issues quickly made people realize that there were better legumes to directly eat, and the use of soybeans in the kitchen generally fell by the wayside.
The problem, though, was not soy itself but rather our lack of awareness of how other cultures had unlocked its nutritive value. In conjunction with domestication, the peoples of eastern Asia developed ingenious ways of removing or breaking down the offending oligosaccharides and trypsin inhibitor to make soy's protein easily available.
We are going to discuss three principle approaches for doing this. First, we'll consider a chemical approach: by grinding soaked soybeans, mixing in water, and then cooking and straining this gruel, it is possible to extract 80% of the protein through the creation of soy milk. The proteins in this milk can then be precipitated though the addition of certain natural chemicals, and when these curds are strained and pressed, tofu is created. This product turns out to be one of the most digestible forms of protein, as the offending compounds have been deactivated, destroyed, or removed.
Second, with tempeh we'll look at a way to make soy digestible via rapid fermentation. In this product, partially cooked soybeans are inoculated with spores from the fungus Rhizopus oligosporus and incubated for about 24 hours. Because of fungal activity, the resulting bean cake is easily digestible and high in not only proteins but also various B-Vitamins.
Last, we'll show with miso – one of the principle flavorings in Japanese cuisine - how to make soy digestible through a slow (2-month to 3-year or longer), complex, two-stage fermentation based on the fungus Aspergillus oryzae and a host of lactic-acid generating bacteria. This is the most involved process that we'll discuss, but is still easily accomplished in your kitchen and back room.
As long as you have some specialized equipment on hand (a food grinder, a tofu press, a food steamer, a food thermometer, and a thermostat-controlled incubator) we have found that these three processes are all easily done in your own kitchen at a fraction of the cost of store-bought products. And, we are never ceased to be amazed at how much food we can create from so little starting product: only 4 cups of dried soybeans (about 1½ pounds) turns into 6 pounds of high protein, easily digestible, low fat, healthy food (2 lbs of tofu and 4 pounds of tempeh). We are even able to use the leftover whey as a soap and bath treatment. Nothing from these beans is allowed to go to waste. For us this is a process reminiscent of a loaves-and-fishes miracle.
We will be relying heavily throughout this month on three books by William Shurtleff and Akiko Aoyagi of the SoyInfo Center: The Book of Tofu, The Book of Miso, and The Book of Tempeh. These are encyclopedic treatments on making and cooking these three soyfoods, and are literally the last word about each. All we can do here is briefly summarize the information presented in detail in these books. We cannot recommend strongly enough that if you find the following entries of interest you track down and purchase your own copies. Unfortunately, all three are now out of print, but on-line versions are available from the Soyfoods Center website, and second-hand copies are available via the internet. Also, we were initially inspired to try and make our own tempeh and miso from Wild Fermentation by Sandor Katz. This book still is in press and is also a good and useful read.