Assessing the occurrence of barley starch annealing under heat, moisture and time conditions relevant for kilning: An experimental design approach

Abstract

In this work, the possible occurrence of barley starch annealing under kilning conditions was investigated. Using an I-optimal response surface methodology, the impact of temperature (45–55 °C), moisture content (30–50%) and time (1–5h) on the gelatinisation behaviour of starch in green malt was studied. An increase in onset (0.5–4.3 °C) and peak temperature (0.5–2.7 °C) and a change in peak width (+0.5 to - 3.2 °C) of the starch gelatinisation endotherm showed the extent of annealing that occurred within an industrially relevant design space. Temperature was the main driver behind the observed changes, but also interaction effects between temperature, moisture content and time contributed. Combined with increasingly high starch gelatinisation temperatures in barley, the observed increases in peak gelatinisation temperature due to annealing could hamper fermentable sugar production during brewing.