"Black or brown anthocyanin pigments have undesirable effects on protein and oil extractions of soybean, therefore, most cultivated soybean varieties have been selected for a yellow, nonpigmented seed coat."
i may not really understand all of the chemistry of such papers, but i do enjoy coming across tidbits like this which explain the "whys".
Post by prairiegardens on Dec 31, 2019 17:45:04 GMT -5
Apparently faba beans share this characteristic of seed coat predicting the digestibility of the bean... the lighter the coat the better from our belly's point of view. Even seed catalogs sometimes offer a wealth of tidbit information.
Post by blueadzuki on Dec 31, 2019 20:13:41 GMT -5
It's common to MOST legumes. When's the last time you saw a non-heirloom soup pea (defined here as any pea you are eating dry mature seed as opposed to as a snap or shelly) whose seed coat wasn't white. It's because the darker colored ones tend to have more of the things that can make peas bitter or otherwise unpleasant (colored seed coats are also often thicker than white ones, so there's that as well.) For some beans (like lupinis and lablabs) a colored coat often signifies that the seed has enough stuff to be poisonous when mature, and needing of leaching to be made edible)
In the case of soys, it's more of a cosmetic thing. Those anthocyanins will stain the extracted oil or protein. Undesirable if you want clear yellow soy oil, soy meal that wont be visible, or snow white tofu. You can get around it by dry processing the beans (skinning them when they are still dry as opposed to after they have been soaked). But that is a lot more labor intensive than doing it wet so not done as much.
Ironically I understand there is some research that indicates that black skinned soys may be easier to digest than yellow ones.
By and large, colored skinned soys tend to be for the market for things like black bean sauce and soy sauce (which wind up brown anyway, so no big deal) or for the edamame market (where the beans are consumed young and green, so no one cares what color they turn when ripe).
It's sort of like the situation with green cotyledoned soybeans. Soybeans can have the same recessive gene as peas that allows the insides to stay green. However, barring mutations, you will tend to only see this in colored skinned soybeans. Its the same reason, no one wants to eat green tofu or drink green soy milk. But in the coloreds, it's not a big deal, since the products all end up deeply colored anyway. In fact, in the soy industry it is the norm to find yellow and green inside soys mixed together with no distinction (depending on season and area green soy can often make up the majority of the crop.)
i'm sure there is a lot of variability as i've experienced it here directly. the soybeans grown in the fields around us weren't all that great for making soymilk or tofu or for eating but i picked up some from a health food store to grow out and the next year's crop was good for any use i put them to.
i grew soybeans for about six years but i don't make soymilk or tofu any more - i decided i'd rather drink water and avoid all that processing. i cannot grow Edamame soybeans easily with all the chipmunks we have around here. my last attempt i planted and replanted 300 seeds and got about 24 seeds in return.
i still do eat a lot of beans. i'd better since i grow so many of them! i cook them without pre soaking. my body doesn't seem to mind them at all no matter what the color. i do like the different textures and flavors of beans and most of the time i cook them in water only. once in a while we make something else like we're just polishing off a pot of the leftover Christmas ham & yellow eye beans soup. delicious!
Last Edit: Jan 1, 2020 15:09:14 GMT -5 by flowerbug