Pattern of enzyme hydrolysis in raw sago starch: effects of processing history

Abstract

Hydrolysis patterns of five batches of sago starch were studied by using Novo Nordisk and Sigma α-amylases and glucoamylases. Native sago starch was a poor substrate to the enzymes and the hydrolysis patterns were surface erosion, pitting and crevassing. After incubation with pH 3·5 acetate buffer at 60 °C for 2 h, the hydrolysis pattern was different: a single deep round hole developed regardless of the batch or enzyme(s) used. This step also significantly increased the degree of hydrolysis. Granule size distribution results indicated that at about 67% hydrolysis, treated granule residues were the same mean size as native granules while untreated granule residues had two major size populations. DSC results suggested that amorphous regions of the untreated granule were preferentially hydrolysed, however, upon pretreatment regions within the granule were more uniform towards enzymes' action.