DEVELOPMENT OF A MASHING PROFILE FOR THE USE OF MICROBIAL ENZYMES IN BREWING WITH RAW SORGHUM (80%) AND MALTED BARLEY OR SORGHUM MALT (20%)

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Abstract
Different time and temperature programmes were used to evaluate the production of hot water extract (HWE) and free amino nitrogen (FAN) from mashes containing raw sorghum and either malted sorghum or malted barley in the presence of microbial enzymes. Two malted varieties of sorghum (SK 5912 and Zaria) were used. The former gave higher HWE but lower FAN than the latter. Sorghum malts were unable to provide enzyme activity for starch extraction and exogenous enzymes were always needed. Seventeen commercially available enzyme preparations were assessed. A double-mash process was developed. Inclusion of calcium ions (200 ppm) was beneficial but adjustment of mash pH had little effect. Raw sorghum was gelatinised at 100°C for 30–40 min in the presence of a heat-stable α-amylase followed by mixing with a malt mash (started at B0°C) to give a temperature of 65°C with a total mash time of 167 min (127 min from mixing the mashes). The inclusion of a single commercial enzyme preparation (containing both proteolytic and amylolytic activities) was sufficient to achieve satisfactory HWE and FAN. Addition of different activities or combinations of activities gave no significant advantages. To obtain levels of FAN of 100–140 mg/l however excessive amounts of enzymes were required.

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