• Traditional soya foods
  
  - Non fermented products
  
  - Fermented products
• Second generation soya foods (western style)

Traditional soya foods

Traditional soya foods can be divided in non-fermented and fermented products.

Non fermented products

Soya drink :

• The main non-fermented traditional soya food is soya drink itself (also known as tonyu, the Japanese word for soya drink).

The traditional process :

• Whole beans are cleaned and soaked with water overnight.
• Water that has not been taken up by the beans is drained.
• The swollen beans are then wet milled with fresh water to produce a fine slurry.
• Next step is to separate all the insoluble material (cell wall debris, consisting of polysaccharides of the pectinic type) from the soluble material (protein, sugars and, minerals). This is traditionally done with a cheese cloth. The insoluble material (called okara) is removed and used for animal feed or in bread baking.
• The resulting soluble material is a milky emulsion better known as tonyu, the Japanese word for soya drink.

Traditional soya drink has a distinctive beany taste, which is accepted by the Chinese but has never been accepted by the Western palate. The reason for this bitter and astringent taste is uncontrolled enzyme activity. The oxydation reactions catalysed by the lipoxygenase enzyme system, whereby oxygen reacts with the double bonds of the poly-unsaturated fatty acids are not under control in this process.

One of the first improvements been brought to this traditional process was the simple principle of hot grinding. The technology was developed at the Cornell University in the late 60s by Hand et al. It consisted of milling the soaked beans with hot water (above 80ƒC). By doing so the enzyme lipoxygenase, which is rather heat labile, is partly deactivated and the damage it can do is significantly limited.

In the 70s another improvement was brought about by researchers of the University of Illinois (Nelson, Wei and Steinberg). It consists of blanching the beans before they are wet milled. This eliminates all lipoxygenase enzyme activity before the cells are damaged during wet milling. In this process, whole beans are used and sodium bicarbonate is added to the blanch water to tenderize the beans. The slurry is subsequently high pressure homogenized offering a high yield.
The problem was that they tried to keep all the components of the bean in the drink (whereby no okara was removed). The mouthfeel of this "Illinois soya drink" was very chalky and sandy.

It was in the next decade, i.e. in the 80s that the European market leader in soya foods Alpro soya developed it's own process for soya drink production, which brings an optimal taste.
It is worth mentioning that soya drink substitutes have been developed based on the use of "reconstituted soya drink" which are based on soya protein isolates. It is important to stress the fact that these "engineered soya drinks" are based on the principles of "mixing components together to obtain the end product" and of "adding back the nutrients" instead of "keeping the nutrients in the product".
These soya protein isolate based soya drinks are normally composed of isolates with added refined soya bean oil to which an emulsifier (mostly soya lecithin) is added; a stabilizer is also used to avoid creaming problems.

Tofu

The second most important non-fermented traditional soya food in volume is tofu, better known as traditional soya cheese. Tofu is coagulated soya drink. There are essentially 3 types of coagulation agents: the most popular one in China is nigari (produced as a by product in the process of sea salt production from sea water; it is the magnesium chloride rich portion of the minerals contained in sea water). Calcium salts such as calcium sulphate and or calcium chloride can also be used in tofu manufacturing.
More recently new formats of tofu have appeared on the market: silken tofu is lower in protein than traditional pressed tofu and consists of homogeneously coagulated soya drink whereby the coagulation is done in the packaging and using glucono-delta-lactone as a (slow speed) coagulant.

Fermented products

The most popular traditional fermented soya foods are: tempeh, shoyu and miso. Tempeh is based on fermentation of soaked soya beans that are inoculated with a Rhizopus oligosporus strain (edible mould). It is "the Camenbert of the far east" and is very popular in Indonesia.

Shoyu

• Shoyu is better known as "soya sauce", very popular in China and Japan. It is produced from a mixture of soya beans and wheat and is based on the use of the Aspergillus oryzae strain.

Miso

• Miso is a fermented mixture of soya bean with rice or barley and is also made with the use of the Aspergillus oryzae strain. Different products with different tastes and colours are obtained due to differences in fermentation temperature, time and different salt concentrations.

tempeh

• Apart from the tempeh fermentation, which only takes 2 days, all the other fermentation processes for traditional fermented soya foods take months to come to an end. Delicate flavours are produced whereby a natural hydrolyzation process takes place. During this hydrolyzation process the larger molecules (protein, carbohydrates and fats) are broken down to smaller molecules.

Natto

• Natto are cooked whole soya beans fermented with Bacillus natto. Soft beans covered by viscous, sticky polymer, distinct aroma

Second generation soya foods (western style)

Over the past few decades, new "second generation" Western style soya foods have been developed. Almost all of them are based on soya drink. In the literature one can find a detailed description of all the incremental improvements that have been made when beginning with the traditional soya drink process.

Dairy analogue products have been developed from this basic soya drink since :

1. Alternative for yoghurt (yofu*)
2. Ice desserts
3. Alternative for dairy cream
4. Desserts/Pudding/Custard

*Yofu is yoghurt-like product made by fermentation of the soya drink with the yoghurt strains. It comes in different flavours as all kinds of fruit preparations can be added after the fermentation process