Comparison between amylose-free and amylose containing potato starches

摘要

This paper describes the comparison of potato amylose-free starches obtained by two different approaches: mutation induction of the gene encoding the key-enzyme in amylose biosynthesis Granule Bound Starch Synthase, (GBSS) and antisense inhibition of the expression of GBSS, with that of normal amylose containing potato starch. One of the most prominent differences between the amylose-free and amylose-containing starches was their phenotype after staining with iodine. The amylose-free starch obtained via mutation induction stained completely red whereas the amylose-free starch obtained by the antisense approach always had a very small dark-blue staining core in a further entirely red staining granule. Amylose-containing starch stained blue with iodine. Differences were also observed with regard to the absence of GBSS protein and activity in the amylose-free potatoes. Furthermore the lambda max and the blue value of the amylose-free starches was markedly different as would be expected since they almost completely lacked (<0.1%) amylose in both types of amylose-free starches. Determination of a number of different chemical parameters including particle size distribution, ion content, as well as phosphate levels of the starch indicated that these were not different in the amylose-free containing starches as compared to the normal amylose containing starches. The absence of amylose resulted in improved gel stability and paste clarity of gels even after prolonged durations at 5 degrees C and at room temperature.