Image analysis and quality attributes of malting barley grain dried with infrared radiation and in a spouted bed

Abstract

SummaryThe impact of drying two spring barley cultivars (Mauritia and Prestige) in a spouted‐bed and in infrared radiation (IR) dryers on grain dimensions, colour, pigment content, vitality and malt quality was investigated. The results indicate that the investigated drying methods led to kernel dimension changes. Kernel shrinkage was typical of spouted bed drying, while kernel expansion was observed after IR drying at the intensity of 900 W m−2. An increase in the intensity of yellowness (b*) on the surface of dried grain and a decrease in the yellowness intensity of kernel cross‐section were also observed. The aforementioned changes were associated with the decomposition of carotenoids (endosperm colour) and reduction of soluble proanthocyanidin and total phenolic compounds (surface colour). The drying processes also lowered germination energy and capacity, in addition to susceptibility to moisture diffusion into the endosperm. These adverse results were cultivar dependent and affected the quality of malt and wort only to a limited extent. The main changes were an increase in the Kolbach index in malt from Mauritia cv., and a fluctuation of the diastatic power of malt that did not exceed ±3%. Generally, drying of barley grain in spouted bed should be conducted at an inlet air temperature of 40 °C and using an IR drier at a radiation intensity of 600 W m−2.