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New corn starch hybrids broaden functionality choices.

Several years ago, scientists at a major Midwestern corn starch supplier's research laboratories asked themselves: "How can we achieve functional modification of corn right on the plant--instead of in a chemical plant?" They also asked themselves: "Why should we bother to commercialize a new variety of starch, with all the choices already available to food processors?" The answer to the second question was simple--to meet the changing needs of the customer. The first question has not been completely answered, but significant steps have been taken towards solving this problem.

The first announcement of successful commercial introduction of food starches naturally modified was described in the December, 1989 issue of FOODS OF TOMORROW Magazine. This was accomplished by using standard genetic plant breeding and selection techniques to provide the same functionalities formerly offered only by chemical modification. Development was the result of a 5-year research program that combined a variety of genes, including waxy (wx), amylose extender (ae), dull (du), sugary (su), floury (fl), and hard or horny (h), which control a spectrum of starch characteristics.

Since the original goal of sourcing useful corn polymers from all over the world was begun, 10 genetic starch varieties having functional characteristics have been patented. These were bred into hybrids offering adequate yield for commercial interest. The amylose and amylopectin were the two basic components of the corn starch considered most important in this program. All characteristics of these biopolymers were studied extensively to determine the controlling factors of different functional characteristics.

Several factors affecting performance of starch polymers were identified. The ratios of these polymers and their structures control both the physical characteristics and their cooked starch paste characteristics. (Single and multiple mutants of maize offer the most extensive and varying range of these polymer-containing starches.) Besides the genes already described--amylose extender, dull, floury, sugary, waxy, and horny-- others important to this concept include brittle, opaque, shrunken, and white.

These genetic characteristics may then be translated as functional characteristics of starch and starch solutions. The descriptive terms would then include viscosity, gel strength, shear stability, freeze/thaw stability, acid stability, gelatinization temperature, digestibility, clarity, and ingredient interactions.

Application testing

New starches showing unique characteristics have been selected and subjected to product application testing. For example, the double recessive dull waxy (duwx) variety yields an amy-Iopectin starch different from commercial waxy starch. It has a slightly higher pasting temperature, with the paste having a less cohesive or stringy texture and slightly higher gel strength. These characteristics are important in its recommended use for replacing modified starch in instant puddings and mousses.

The reduced viscosity exhibited during cooking will allow usage in microwave baking of cakes. Addition of duwx to the formulation improves crumb structure and uniform moisture distribution. And, these attributes maintain a mouthfeel similar to that of an ovenbaked cake.

Dull waxy hybrids of amy-Iopectin starches can retrograde and produce unusual interactions with other food ingredients. Although waxy starches have limited, if any, freeze/thaw stability, starch from the waxy shrunken double mutant has demonstrated the ability to withstand 10-15 freeze-thaw cycles when used in systems that contain some sucrose. Gels of this starch also possess exceptional clarity.

Lower cooking temperatures Some of the newest naturally modified varieties are high amylose-type starches that can be processed at lower cooking temperatures. Normally, these starches have high cooking temperatures and usage is limited to products produced with very high temperatures (e.g., food coatings, setting agents in confections). But, by combining starches from two of the double mutant high amylose starches (amylose extender, dull, and dull horny), a lower cooking temperature characteristic results and wider food application is possible.

Examples of where this could be applied include fried donuts, where low-temperature gelatinizing high amylose starches increase the cake volume with no effects on taste, texture, or oiliness of the finished products. The processing temperature for starch jelly candy production could also be significantly reduced with use of this amylose extender dull starch.

Understanding and being able to control different functional attributes of selected food starches in food systems offer promise for both the modification of starches and for their application in foods. These starches are considered to be particularly applicable in reduced fat systems, microwavable foods, and other newer processes.

Additional information on New Genetically Modified Food Starches is available from American Maize-Products, Inc., 1100 Indianapolis Blvd., Hammond, IN 46320-1094..
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Title Annotation:naturally modified corn starches
Author:Duxbury, Dean D.
Publication:Food Processing
Date:Dec 1, 1992
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