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Soymilk is the base product from which
all the soya-dairy foods are made. Together with its most
common derivative, tofu, it is the best-known and the longest-established
soyfood product. When we describe soymilk processing, we are primarily
referring to a soymilk base, which is the pure soymilk extracted
at the end of the process. Consumer packages of "soymilk drink"
and "beverage", etc. are formulated from this base, with other ingredients,
to either imitate the taste and functionality of cow milk, or to
make flavored drinks such as vanilla or chocolate.
Traditional Processing
of soymilk was started by the Chinese, as long as 2,000 years ago.
Today the same method, or modern variations of the same basic process,
are still used in Asia and by many tofu producers in the rest of
the world. This traditional method, which is also the simplest and
least expensive, can be done both manually, in a simple kitchen,
or by commercial equipment in a modern plant. This process has four
steps:
- Soak
soybeans (4-12 hours depending on water temperature)
- Grind
soaked soybeans into a mash or pulp (Stone/manual grinding, electric
blending etc.) with the addition of water.
- Cook
the resulting slurry (Stove top or commercial steam injected vessels).
- Separate
the cooked soymilk from the remaining "Okara" fiber. (Filter press
or centrifuge.)
Modern Processing methods have
evolved for a number of reasons; the main one being to eliminate
or reduce the "beany" off-flavor, present with traditional processing.
This taste has been proven to be unacceptable to most non-Asian
consumers, particularly since their use of soymilk is as a replacement
for cow milk and hence a neutral, non-beany taste is preferred.
The taste issue is largely due to the activity of the lipoxygenase
enzyme, and the inactivation of this is one of the major objectives
of modern processing systems.
Additionally, production capacity, sanitation and functional versatility
(variety of flavors and other value-added products) are other factors
which have determined the configuration and capability of modern
systems.
Competing Methods are available for modern
processing. Most modern technology is designed to:
a) eliminate or reduce the problem "beany" off-flavor and,
b) optimize yield and functionality.
These competing technologies employ various methods and principles
including: hot grinding of soaked soybeans, cold grinding of soaked
soybeans, hot blanching, dry bean grinding and others. With some
methods, the problem flavor is controlled, but the product yield
goes down. With others the result is good flavor but poor "mouthfeel"
, or unsuitable functionality for other derivative foods. Finally,
many major processors design either hybrids or variations of these
methods, with or without their own innovations. For some consumer
products, the final soymilk is "deodorized" with vacuum systems,
prior to formulation and packaging.
The complexity of performance claims and the processing options
are the greatest challenge to the new soymilk processor or for the
upgrading of existing facilities.
Traditional vs. Modern methods
is a fundamental issue facing processors, particularly those in
developing countries and those who will begin production with a
medium capacity in the range of approximately 200 to 300 Liters
per hour. For some products, such as tofu and yogurt, it is not
necessary to eliminate the beany off-flavour and so the processing
line can be simpler and more cost-effective. (Essentially using
the traditional method, with modern equipment.) Another factor is
the kind of packaging that will be used for the finished product.
Ultimately there are a number of overlapping considerations that
determine how complex a system needs to be for any given processor.
However, it is safe to conclude that a processor planning to produce
a "non-beany" soymilk drink, in a long-life consumer package, will
have to acquire the more complex (and more expensive) production
technology. Yet, even for this category, there are cost-effective
solutions available and even at medium-capacity production. Ultimately,
local tastes and market considerations will determine not only the
kind and variety of soymilk and soya-dairy products that should
be produced, but also the type and complexity of equipment and know-how
required. For these reasons, a careful analysis is required that
reflects the local market and financial conditions.
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