Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
The organic matter removed with the light phase is used in liquid or dried form as
feed. Wheat bran, for example, is mixed with such effluents and concentrated process
water to prepare high-value feed, the wheat gluten feed.
8.4 POTATO STARCH
8.4.1 GENERAL REMARKS
Although potato (Solanum tuberosum) is grown on different continents, the utilization
of potatoes for starch production is concentrated in the European countries. The
main producers are situated in central Europe, in particular The Netherlands, Germany,
and France. Poland and Russia are producers too. As mentioned earlier, starch
production from potatoes cannot compete with that from other raw materials as
regards the economic support required by coproducts and well paid in food and
other industries. Because of alternatives in some regions of middle and eastern
Europe, the production is still subsidized but also limited by a politically fixed system
of quotas. 19,20
8.4.2 SUBSTRATES
Potato starch factories buy potatoes on the basis of weight and starch content. 21 Both
figures are determined for each delivered load immediately after entering the plant.
In general, in-plant installed automatic sampling systems take samples from each
lorry, at least two independent probes of up to 50 kg of tubers. The tubers are washed
in automatic washing systems and inspected for general tuber quality. Finally, the
tuber starch content is determined by underwater weighing. In terms of long–term
selection, the starch content of potatoes preferred for starch production ranges from
17 to 19%, although tables established for regulating payment on the basis of starch
content allow use of potatoes having a starch content from 13 to 23%. Annually
established E.U. tables, for instance, describe the minimum price as well as subsidies
based on starch content within the described framework. 21
8.4.3 PROCESSES AND ALTERNATIVE PROCESS STEPS
8.4.3.1 General Remarks
From an engineering point of view, potatoes are a relatively uncomplicated product
for starch extraction. Because potatoes are generated by secondary growth of subterranean
shoots, their tissue structure is relatively soft in contrast to that of root
tissue. Deposition of starch granules occurs in cells filled with fruit water, and the
overall composition of potato starch in situ is uncomplicated. These facts make the
starch accessible by simply disintegrating tubers by small mechanical forces, followed
by washing out the interior content of cells, separating the starch, washing,
and drying. A stable, but not valuable, commodity product of high purity and
versatility can be recovered this way. Although the process itself seems simple, the
production of potato starch has to overcome several serious obstacles that burden
its economic success. The first and main problem is the limited stability of potatoes