Gelatinization or pasting? The impact of different temperature levels on the saccharification efficiency of barley malt starch

Abstract

Efficient enzymatic hydrolysis of cereal starches requires a proper hydrothermal pretreatment. For malted barley, however, the exact initial temperature is presently unknown. Therefore, samples were micro-mashed according to accurately determined gelatinization and pasting temperatures. The impact on starch morphology, mash viscometry and sugar yields was recorded in the presence and absence of an amylase inhibitor to differentiate between morphological and enzymatic effects. Mashing at gelatinization onset temperatures (54.5–57.1◦C) led to negligible morphological and viscometric changes, whereas mashing at pasting onset temperatures (57.5–59.8◦C) induced significant starch granule swelling and degradation resulting in increased sugar yields (61.7% of upper reference limit). Complete hydrolysis of A-type and partial hydrolysis of B-type granules was achieved within only 10 min of mashing at higher temperatures (61.4–64.5◦C), resulting in a sugar yield of 97.5% as compared to the reference laboratory method mashing procedure (65◦C for 60 min). The results indicate that the beginning of starch pasting was correctly identified and point out the potential of an adapted process temperature control.