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Starch in microwave cookery.

Starch in Microwave Cookery

While in 1988, slightly more than 40 percent of the UK households were using microwave ovens, the market forecast of more than 60 percent for 1992 indicates that replacement purchase is now the norm. For mainland Europe the present figures are much lower, with expectations for 1992 varying between 25 and 40 percent.

As a result, manufacturers expect a rapid increase in demand for microwave prepared foods. There are also possibilities for powdered foods such as sauces, soups, bakery powders, providing a good instant character can be assured.

Starches are currently used in these prepared food and powders. A manufacturer can use the same starches in microwave prepared foods as used for foods heated by conventional ovens. For shelf stable products, crosslinked and crosslinked acetylated waxy maize starches have the necessary heat, shear and acid stability to create foods with the right viscosity and texture. For chilled and frozen foods, crosslinked acetylated waxy maize starches are advised because of their freeze/thaw stability.

When developing microwave foods containing starch, some rules should be considered: Starch acts in a formulation to bind water and hence allows conduction to take place. A starch paste will tend to increase in temperature more quickly than a similar amount of 'free' water. The more concentrated the starch paste, the quicker it heats up, providing there is sufficient water to gelatinise the starch. An extreme example of the benefit of starch binding the water is that it does not allow migration and hence retards steam formation.

Similarly, melt away can be controlled in frozen foods. When starch is used in components of prepared meals, the influence of starch concentration on heating speed should be considered in order to ensure an homogeneous distribution of heat through the meal.

In food systems where microwave heating is used to swell starch, the influence of other ingredients on starch gelatinisation should be taken into consideration. Whereas in normal cooking, fats and salt tend to inhibit starch swelling, in microwave system they can actually facilitate it. Sugars behave similarly in both systems, competing with starch for the available water and thus impairing swelling. These characteristics must also be considered when formulating a dry mix for microwave use. For these applications the situation becomes more complex so that starch types, compositions and concentrations should usually be adapted to the food product type and preparation method.

Research shows that when microwave cooking is used to prepare, for example, sauces from dry mixes, dispersion and suspension of ingredients are essential. Pregelled modified starches with adapted granulometry will ensure better dispersion, avoiding lumping and building up the desired viscosity and texture within the short heating times typical of microwave cooking.

Microwave formulation development work takes place at the bakery department of Cerestar's food application centre at Euro Centre Food. Cake mixes have been developed allowing the preparation of pound and sponge type cakes baked for 3 to 4 minutes in a 600w microwave oven. Trials with a 25 percent substitution of wheat flour by different native starches indicate that wheat starch and waxy maize starch give the best results. The latter also gives an improved shelf life because of its high amylopectin content. According to other tests on modified starches, slightly crosslinked waxy maize starch gives the best overall results.

Pregelled starches are used to control dough viscosity and to prevent early carbon dioxide release in the dough. There is also a need to adapt the baking salt composition. Storage stability of cakes is further improved by using an adapted emulsifier, eg sucrose palmitate.

References

Southern S. - Marketpower Ltd Prospects of Microwave Foods in UK and Europe, lecture given at MW Foods 1989 conference held in in London in June Howling D. - Cerestar UK Starches in the Microwave age, lecture given at MW Foods 1989 conference held in London in June Timmerman H. - Cerestar ECF, The Netherlands The use of starches in microwave baked cakes, lecture given at FIE conference in Paris, in September 1989
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Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Author:Rapaille, Andre
Publication:Food Trade Review
Date:Jun 1, 1990
Words:664
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