A Simplified Isolation of High‐Amylose Maize Starch Using Neutral Proteases

AbstractBreeding projects aimed at increasing starch amylose would benefit by having a rapid starch extraction method requiring only non‐hazardous reagents and leaving the native granule intact for functional analyses. A study was, therefore, designed to investigate the use of a neutral protease for the removal of protein during the starch extraction process from the grain of high‐amylose corn. Sets of F2 ears presumed to be homozygous for the recessive amylose‐extender (ae) allele and segregating high amylose modifier gene(s) were used in the study and ranged in amylose content from 55% to around 70%, although several non‐mutant genotypes (˜25%) occurred because of visual misclassification of the ae kernels. Starches from samples were all initially extracted by grinding and filtering, then further treated in three ways including either 1) no protein removal, 2) toluene and saline washes or 3) use of neutral proteases. In general, amylose values corresponded among samples extracted using the three methods. Samples purified using proteases had higher mean amylose values (62.5%) attributed to the lower presence of contaminating protein compared to samples prepared with toluene (61%) and grinding/filtration only (57.5%). Little change occurred among the starches as a result of the protease treatments according to thermal properties obtained using differential scanning calorimetry. In addition, gel permeation chromatography profiles (GPC) were unaffected by this treatment. A low level of amylase activity from the protease was found which degraded less than 1% of the starch sample. The results demonstrated that this protease method gave an increased yield of starch with a quality similar to that of starch prepared with toluene.