What is soy yogurt?
Soy yogurt is made by fermenting soymilk with friendly bacteria, mainly Lactobacillus bulgaricus and Streptococcus thermophilus. The process is similar to the production of yogurt from cow milk. Yogurt production was invented probably by accident by Balkan tribes thousands of years ago. Yogurt remained mainly a food of Eastern Europe until the 1900s, when the biologist Mechnikov theorized that lactobacillus bacteria in yogurt are responsible for the unusually long lifespan of the Bulgar people. Mechnikov then popularized yogurt as a foodstuff throughout Europe.
The sugars are fermented by the bacteria into lactic acid, which causes the formation of the characteristic curd. The acid lowers to pH of the yogurt to about 4.0 and restricts the growth of food poisoning bacteria. The bacteria produce lactase which breaks down the lactose in dairy milk. Soy milk does not contain lactose but other sugars such as stachyose and raffinose.
Some countries only allow to use the name "yogurt" for products which have not been pasteurized to kill the bacteria after fermentation. This "live" yogurt is believed to be nutritional superior. The living bacteria are supposed to improve our immune system and the enzymes help to digest food. Sometimes, special probiotic bacteria, which are supposed to improve our gut health, are added to dairy or soy yogurt. These probiotic bacteria, often called good bacteria, are special strains of lactic acid bacteria or Bifidobacterium. A probiotic yogurt contains additional ingredients, such as inuline, that promote the growth of the probiotic bacteria. Soy yogurt always contains natural probiotics: the two soy sugars, stachyose and raffinose, act as probiotics and stimulate the growth of Bifidobacterium in the large intestine. Foods that contains both probiotic bacteria and prebiotic ingredients are called symbiotics.
It is difficult to find soy yogurt in supermarkets but you may find it health food shop. Or you can make soy yogurt at home. You can use store-bought yogurt as starter or even Solgar capsules that contain Lactobacillus bulgaricus and Streptococcus thermophilus. In some countries, soy yogurt is labelled as "cultured soy milk" because the term "yogurt" is reserved for dairy yogurt.
How to make soy yogurt
This step is not necessary if you start from bought soy milk. Put the soybeans (ideally split soybeans) in a pan and poor 3 liter boiling water over them. Let it cool down and wait 6 to 12 hours. Drain the beans, add 1 liter cold water and mix it in a blender for 3 minutes. Remove the soymilk from the solids by squeezing the mixture through a cheese cloth. Bring the soymilk to boiling point and continue to boil for 10 minutes.
Culturing the soy yogurt
Cool the soymilk down to 42-45°C (either by cooling the boiled soymilk or by heating the bought soymilk). The culture will only thrive in a narrow temperature range, too cool and it won't be active, too hot and it will die. Measure the temperature with a thermometer. Add 4 tablespoons of starter to the soymilk and mix well with a sterile spoon. Put the yogurt in a yogurt maker cups and follow the same directions as for dairy yogurt. If you don't have a yogurt machine you can put the yogurt in an oven at 42-45°C. After about 5 - 6 hours, when the yogurt gets firm, chill the yogurt.
Making the soy yogurt thicker
You will notice that home made yogurt will be a little runnier than dairy yogurt. To improve the thickness of soy yogurt you can add one level teaspoon of agar powder or two teaspoon starch, premixed in 50 ml water, to the soymilk when it starts boiling. The best option is to add extra soy protein, at least if you can get hold of it. One tablespoon soy protein should be added to one liter soy milk before boiling.
How to make soy milk?
It's very easy to make soy milk at home. If you make soy milk on a daily basis you might find an automatic soymilk maker (also called soy milk machine) such as Soyajoy, Soylife, Miracle, Soyquick, Soyawonder or Vegan Star very helpful.
You need about 125 g whole soya beans to make 1 liter of soy milk.
Step2: Soaking and dehulling the soya beans
Clean the soya beans and soak them in water for 10 - 16 hours. Although not necessary, you can remove the hulls be kneading the soya beans and flushing the loose hulls with water. Removing the hulls makes the extraction process more efficient. An alternative is to crack the soya beans before soaking. The hulls come loose easily and can be washed away. When you use cracked soya beans you need less soaking time: 6 - 8 hours.
Step3: Heating the soya beans (optional)
Heating the soya beans will destroy enzymes which are responsible for the development of beany flavour. This heating can best be achieved by microwaving the wet soaked soya beans during 2 minutes.
Step4: Grinding the soya beans
Grind the soaked soya beans and 1 liter water in a blender. Sieve the mixture trough a cheese cloth and recover the soy milk. The insoluble material which remains on the sieve is called okara, and can be used as an ingredient for bread making or as cattle feed.
Step5: Boiling the soy milk
Heat the soy milk till boiling point and continue boiling for about 5 to 10 minutes. After cooling, the soy milk is ready and can be kept in the fridge for another 3 days.
Step6: Flavouring the soy milk (optional)
The soy milk can be drunk as such but taste can be improved by adding some salt (also cow milk contains a lot of salt).
With soy milk you can easily make your own fruit smoothie. Fruit smoothies are very healthy because they contain soy milk and a lot of fresh fruits
500 g ripe papaya (the papaya is ripe when skin is soft and smells fruity)
500 ml soy milk
2 medium bananas, peeled, cut in slices
250 ml orange or pineapple juice
1/2 lemon, squeezed
2 tablespoon honey (optional)
Remove the seeds and peel from the papaya. Cut the papaya in cubes. If you have time, first freeze the papaya and banana, this will give smoother drink. Combine the banana, papaya and soymilk and mix with a blender until smooth. Add the honey and fruit juice and mix again.
Bring the papaya smoothie to taste with the lemon juice.
Pour the papaya smoothie in long glasses and serve with a bit of ice.
The papaya (Carica papaya) is a pear shaped tropical fruit, which grows the whole year rond on palmlike trees. The skin is green when unripe and becomes yellow to red when the papaya gets ripe. The inside of the papaya is filled with black wrinkled seeds, which are normally discarded. The ripe papaya has a very typical sweet flavour with a musky note. The papaya has spherical or cylindrical shape and can weigh up to 12 kg.
Papaya is known for its digestive enzyme papain. This proteolytic enzyme aides digestion because it breaks down complex proteins. This is why papaya is used as a meat tenderizer. The activity of the papain will be lost when the papaya is cooked. The papaya is also a rich source of vitamin A, vitamin C, potassium and fibre.