Soy protein concentrates
There are basically 3 processes to produce soy protein concentrates. They all use a different "protein immobilising principle". Indeed the trick is to make the protein insoluble during the extraction of the other water soluble components (i.e. the oligosaccharides).
One way of doing this is by heat treatment of the "white flakes" (i.e. the residue obtained after the oil extraction, which is normally the starting material for the production of soy protein concentrates and soy protein isolates). The name "white flakes"originates from
the fact that while the oil is removed by extraction, the carotenes are removed as well and the extracted residue gets a typical white colour. In this heat denaturing process the tertiary and quaternary structure of the protein are changed and they become water insoluble
before the extraction process begins. This process is no longer used today because the protein has lost (irreversibly) most of its functional properties and because of the microbiological problems encountered in the process.
The second way to make soy protein concentrates is by using isoelectric extraction
conditions. These conditions are obtained by using acidified extraction water.
By doing so a pH is obtained whereby the soy protein has its lowest possible
solubility characteristics. After the extraction the neutral pH can be restored
by neutralisation and the protein regains its original solubility characteristics
and functional properties. This process results in the best tasting and most
functional soy protein concentrates that have found applications in the
preparations of fat emulsions for use in emulsified meat preparations for example.
The third process for making soy protein concentrates is the process that uses
alcohol water mixtures for the extraction of the oligosaccharides. This is the most
popular process because it results in the most bland tasting and nutritionally most
attractive soy protein concentrates. This process is based on the (irreversible)
alcoholic denaturation of the protein.
Soy protein isolates
Soy protein isolates are pure soy protein which has been isolated from their
original cellular matrix. The oligosaccharides (low molecular "sugars") as well as
the polysaccharides (cell wall material) have been selectively removed from the
meal after the fat extraction. These highly purified products are also used in meat
applications for their water binding and gelifying properties.
The process to make soy protein isolates is a 3-step process : The starting material
is again the "white flakes".
In the first stage the flakes are slurried with water under alkaline conditions so
that the protein (which become more soluble under these conditions of pH) as well
as the oligosaccharides can go into solution. The polysaccharide containing
unsoluble residue is then removed by centrifugation.
In the second stage of the process the supernatant liquid of stage 1 containing the
protein and the "sugars" in solution is acidified to the isoelectric point of the
protein (pH whereby their solubility is minimal). This results in the precipitation
of the protein, which can be separated from the oligosaccharide containing
In the third stage of the process the solubility of the precipitated protein is
reversibly restored and they are resolubilized by neutralising after redilution
with fresh water.
Finally this protein isolate solution is spray dried and packed in multilayer paper
Products produced from soy protein isolates and concentrates
All the products we have been discussing up to this point can be considered as
functional ingredients for the food industry and are normally sold in paperbags
to this industry.
Further processing makes it possible to produce structured soybean protein
products such as texturized vegetable protein (in this case extrusion technology is
used) and even spun soy protein isolates have been developed which can simulate meat
fiber structures. TVP is normally used as a meat "extender" and attempts have been
made for the complete replacement of the meat in spun soy protein based meat
Another possibility is making hydrolyzed soy protein : when low degrees of
hydrolyzation are used, highly functional foaming agents can be obtained and when a
high degree of hydrolyzation is used, typical HVP's (hydrolyzed vegetable protein)
are obtained, which are used in soups and sauces as flavour enhancers.
We must not forget the soy lecithin (a hydratable fraction of the raw soybean oil,
composed of phospholipids) which is widely used as an emulsifier in the chocolate
industry. The main component in soy lecithin is phosphatidyl choline.
We will now describe the world of soyfoods, of which soy drink is only one small
example. Within the individually packed consumer goods we can distinguish between
traditional (Chinese and Japanese) and Western style soyfoods.
Traditional Soy foods
Traditional soyfoods can be divided in non fermented and fermented products.
The main non fermented traditional soyfood in volume is soy drink itself
(also known as tonyu, which is the Japanese word for soy drink). The second most
important non fermented traditional soyfood in volume is tofu, which is better known
as traditional soy cheese. Tofu is coagulated soy drink. There are essentially 3
types of coagulation agents available : the most popular one in China is nigari
(which is 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 appeared on the
market : silken tofu is lower in protein than traditional pressed tofu and
consists of homogeneously coagulated soy drink whereby the coagulation is done in
the packaging and using glucono delta lactone als a (slow speed) coagulant.
The most popular traditional fermented soyfoods are : tempeh, shoyu and miso.
Tempeh is based on fermentation of soaked soybeans which are inoculated with a
Rhizopus oligosporus strain (edible mould). It is "the Camenbert of the far east"
and is very popular in Indonesia.
Shoyu is better known as "soy sauce", which is very popular in China and Japan. It
is produced from a mixture of soybeans and wheat and is based on the use of the
Aspergillus oryzae strain.
Miso is a fermented mixture of soybean with rice or barley and is also based on 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.
Apart from the tempeh fermentation, which only takes 2 days, all the other
fermentation processes for traditional fermented soyfoods 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.
Second generation soyfoods
Since a few decades new, "second generation" Western style soyfoods have been
developed. Most of them are based on modern process technologies. Almost all of
them are based on soy drink. In the literature one can find a detailed description
of all the incremental improvements that have been made when beginning with the
traditional soy drink process.
Before we go into all the details of soy drink processing it seems important to
mention that soybeans are a very versatile raw material out of which an endless
number of products can be produced for non food applications as well as for feed
and food applications.
The soybean meal, which is the by-product of soybean oil processing is largely used
for animal feed applications but is also the starting raw material in the process
for making soy protein concentrates and soy protein isolates. It is also the
starting material to make soy flours (with 50 % of protein content), soy protein
concentrates (with 65 % of protein content) and soybean protein isolates (with more
than 95 % of protein content). All these so called soy protein products are used as
ingredients in food applications.
Soy flour exist in 4 different formats :
* enzyme active full fat soybean flour : mainly used in white bread for improving
the colour of the bread crumb (due to the whitening effect of the oxidation of the
carotenes resulting from the enzyme activity of the lipoxygenase enzyme)
* toasted full fat soybean flour : mainly used in bakery applications such as biscuits
(cookies) for reducing the breaking losses
* enzyme active defatted soybean flour : also in bread applications
* toasted defatted soybean flour : in bakery and meat applications
Soy protein concentrates are products derived from soybean meal after extraction of
the soybean oligosaccharides (raffinose and stachyose). They are used in meat
applications for their emulsification properties.
Just to mention a few non food applications : soybean oil is used today in newspaper
printing inks and soybean protein has been used for making biodegradable plastic
materials in the past. New research activity has started in this field recently.
Soy processing in ALPRO
ALPRO has revolutionized these processes by developing a world exclusive process
which has resulted in an unbeatable base drink with unprecedented sensorial
We will now first discuss the traditional process.
* Whole beans are cleaned and soaked with water overnight.
* The soaking water which has not been taken up by the beans is withdrawn to drain.
* The swollen beans are then wet milled with fresh water to produce a fine slurry.
* Next step is to separate all the unsoluble 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 unsoluble
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, which
is the Japanese word for soy drink.
Traditional soy drink has a typical beany taste, which is accepted by the Chinese
but which has never been accepted by the Western palate. The reason why the soy
drink has this bitter and astringent taste, is the result of uncontrolled enzyme
activity. The oxidation 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 which have been brought about to this traditional
process was the simple principle of hot grinding. The technology was developed at
the Cornell university in the late 60's by Hand et al. It consisted of milling the
soaked beans with hot water (above 80ºC). By doing so the enzyme lipoxygenase which
is rather heat labile is partly destroyed and the damage it can do is
In the 70's another improvement was brought about by researchers of the University
of Illinois (Nelson, Wei and Steinberg) which consisted of blanching the beans
before they were wet milled. The idea behind this process was to eliminate all
lipoxygenase enzyme activity before the cells were damaged during wet milling. In
this process whole beans were used and sodium bicarbonate was added to the blanch
water to tenderize the beans. The slurry was subsequently high pressure homogenized
and the inventors claimed 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
mouth feel of this "Illinois soy drink" was very chalky and sandy.
It was in the next decade, i.e. in the 80's that ALPRO developed it's own process
for soy drink production. The basic process concept has been kept secret until today
and has helped ALPRO to become the market leader in the European market.
Other dairy analog products have been developed from this basic soy drink since,
such as yofu.
Yofu is a yoghurt like product made by fermentation of the soy drink with the
classical yoghurt strains (Lactobacillus bulgaricus and Streptococcus thermophilus).
It exists in different flavours as all kind of fruit preparations can be added
after the fermentation process.
Ice dessert is another product which ALPRO has launched very recently.
An alternative for dairy cream has also been developed which contains 18 % of added
soybean oil in which soybean lecithin has been used as an emulsifier.
It is worth mentioning that soy drink substitutes have been developed based on the
use of "reconstituted soy drink" which are based on soy protein isolates. It is
important to stress the fact that these "engineered soy 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 soy
protein isolate based soy drinks are normally composed of isolates with added
refined soybean oil to which an emulsifier (mostly soya lecithin) is added; a
stabilizer is also used to avoid creaming problems.
ALPRO soy drink is naturally produced from the soybeans and therefore it contains
all the naturally present nutrients.
We will now explain the processing steps from the beans to the oil.
As soybeans contain only approximately 20 % of oil it is not economically attractive
to produce the oil mechanically by using continuous presses. Only very small
amounts of organic "virgin" soybean oil is produced that way, but it remains very
expensive and is therefore not used very much. The only way to produce soybean oil
from the beans in an economical way is by extraction. In order to extract the oil
the beans are first cracked into small pieces (each bean is broken into 8 pieces on
average) and after heating these pieces they are flaked between flaking rolls. By
doing so all the cellular structures are damaged and the oil can now be extracted.
The raw soybean oil is then hydrated whereby the soy lecithin is separated by
centrifuges. This process is also called degumming. The degummed oil can then be
further purified by deodorising under vacuum (whereby the volatile off flavours
are removed) and by using adsorption techniques (removal of the non volatile off
flavours and colouring compounds). Finally the so called refined soybean oil is
The refined soybean oil is mainly used as such in salads and inmayonnaises. It is
normally further processed by winterisation (removal of the haze resulting from
the presence of more saturated triglycerides) before filling. If the oil was not
winterised the consumer would be confused when the oil would become opaque after
cooling in winter. This "winter salad oil" remains clear when stored cold.
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