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In this paper some physico‐chemical characteristics of amylose‐free potato starch are described and compared to those from amylose containing potato starches. The availability of these high‐amylopection or amylose‐free starches has opened up new possibilities to assess the relationship between structural characteristics and physico‐chemical properties of potato starch. At the same time it should be possible to determine more precisely the role of the amylose in the starch on several properties and characteristics. In all different analyses it was clear that amylose‐free starch displayed unique properties. Not only was the response to heating much faster; it also occurred at much higher temperatures as demonstrated by viscographs, differential scanning calorimetry and swelling experiments. Rheological analyses demonstrated that gels formed from amylose‐free starch were less rigid, smoother and shorter. The breaking of amylose‐free gels furthermore required much less strength than that of amylose‐containing gels. This aspect was also evident when threads were made from both starches; amylose‐free threads were much shorter before breaking than threads made from amylose‐containing starch.

Amylomaltases or D-enzyme (4-a-glucanotransferases; E.C. 2.4.1.25) are carbohydrate-active enzymes that catalyze the transfer of glucan units from one a-glucan to another in a disproportionation reaction. These enzymes are involved in starch metabolism in plants or maltose/glycogen metabolism in many microorganisms. The amylomaltase of the hyperthermophilic bacterium Thermus thermophilus HB8 was overproduced in Escherichia coli, partially purified and used to modify potato starch. The action of amylomaltase caused the disappearance of amylose and the broadening of the side-chain length distribution in amylopectin, which resulted in a product with both shorter and longer side chains than in the parent starch. Amylomaltase-treated potato starch showed thermoreversible gelation at concentrations of 3% (w/v) or more, thus making it comparable to gelatin. Because of its animal origin, gelatin is not accepted by several consumer groups. Therefore, the amylomaltase-treated potato starch might be a good plant-derived substitute for gelatin.

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