This time I decided to use ½ litre of beans instead of a full litre because of the juggling of pots and containers required by a full litre. It was much easier and faster. We removed as many of the skins as possible to help remove the beany taste and then we boiled them and drained the water 4 times hoping to further reduce the beany taste. Then we puréed them in the blender again. With the blender less full, the puré was much finer. A litre of water was used. Although the mixture was not as thick as last time, I decided to add a ¼ of water to give a bit more soymilk. As with the last attempt, I boiled the mixture at a high temperature setting for 10 minutes stirring constantly. When it came to a boil, I turned the temperature down to simmer and cooked for another 10 minutes stirring constantly.
Straining the mixture was also a great deal easier and faster because of the reduced quantity. As with the last attempt, I decided to do another batch from the puré. I put the puré back in the pot, added a ¼ litre of water, brought it to a boil and put it through the strainer again.
There was a very fine residue that passed through the strainer on the last attempt which tasted like a soft grit. So we decided to filter the soymilk one last time. We decided to use a jelly bag rather than a cheese cloth because it could be reused and cleaned up easily.
The taste was still beany. In fact, it was impossible to tell the difference in taste between this attempt and the last.
After chilling the soymilk, per the above linked article on making stove-top soymilk, I added maple syrup to taste and ¼ tsp of salt.
WE HAVE EDIBLE SOYMILK!
(barely and only if you use it in coffee)
In my research, I’ve come across comments that the quality of the soymilk and its taste are affected by the type of soybeans that you use and their freshness. There are specialty or novel soybeans which are used to produce various soyfoods of Asian origin, such as tofu, miso, soy sauce, natto, soymilk, and tempeh. Other than Laura soybeans, I’ve seen no specific type of soymilk-associated bean available commercially. I will continue to search.
Secondly, and more importantly, I came across information that said to skip the soaking stage and place uncooked beans into boiling water:
In 1969 Mattick and Hand at Cornell made the important discovery that most of the so-called beany flavor in soybeans was not inherent in the beans themselves but was produced by the enzyme lipoxygenase when the split beans came in contact with water. Lipoxygenase could be inactivated and most of the beany flavor removed by either dropping unsoaked soybeans directly into boiling water or by removing any cracked or split beans prior to soaking, then carefully dropping the soaked beans into boiling water.
The beany flavor comes from a reaction involving the enzyme lipoxgenase (not trypsin inhibitor) enzyme, fat, water and oxygen. The method you are using, soaking in water and grinding will produce good quality soymilk but it will have the beany taste. To avoid the beany taste try the following. Take whole, unsoaked soybean and drop them into vigorously boiling water at least a 5:1 water to bean ratio. Cook for 30 minutes prior to grinding. Dehulling will remove the fiber and result in a soymilk with a smoother mouth feel but it will not reduce the beany flavor. Baking soda will improve the mouth feel and flavor of your soymilk but will not affect the beany flavor. Phytic acid is not destroyed by heat, at least not the heat you are using. It does not affect the beany taste.
Soybean hulls contain unwanted substances. Also the hulls are an obstruction to continued processing, especially in the decanter. Soil bacteria are present in the soybean hulls. The hulls should therefore be removed to reduce bacteria count in the soymilk, resulting in better flavour and shelf-life. Soybean hulls contain polysaccharides which should be removed to avoid off-flavours and processing problems caused by foaming. The holding time for heat treatment of the soybeans to inactivate undesired enzymes can be shortened when using dehulled soybeans. This will decrease protein denaturation and browning of the soymilk.
Blanching of the soybeans in a solution of sodium bicarbonate at high temperature starts the inactivation of the bitter taste causing enzyme lipoxidase. This treatment also washes out water soluble oligosaccharides (flatulence causing) and starts the inactivation of trypsin inhibitor (reducing digestibility).
and from the National Soybean Research Laboratory
1. Blanch the beans twice: Bring 4 cups (1 liter) of water to a boil on the stove. Add 1 pinch of baking soda. Drop the whole soybeans directly into the boiling water and blanch for 5 minutes. Drain and rinse the beans with hot water. Repeat this process so that the beans are blanched twice.
2. Grind the beans: Grind the blanched beans with 8 cups (2 liters) of hot water for 3 minutes using a blender on high speed. (If the blender is not large enough, do this in two batches.) Work carefully and be sure the lid is on tight as this is hot.
3. Strain the mixture: Cool the mixture until it is just warm to the touch and filter it by squeezing it through a cheesecloth. Reserve the solids (okara) for another use.
4. Simmer: Simmer the filtered liquid on the stove for 20 minutes. Stir occasionally. If desired, add sugar, salt, and/or other flavorings to taste.
So we will make one last batch of soymilk using a portion of the Laura soybeans that I have and reserve the rest for seed. And we will skip the soaking stage and put the beans directly into boiling water.