ALPHA-GLUCOSIDASE ACTIVITY OF SORGHUM AND BARLEY MALTS

Sorghum malt alpha-glucosidase activity was highest at pH 3.75 while t hat of barley malt was highest at pH 4.6. At pH 5.4 employed in mashin g sorghum malt alpha-glucosidase was more active than the correspondin g enzyme of barley malt. alpha-Glucosidase was partly extracted in wat er but was readily extracted when L-cysteine was included in the extra ction buffer, pH 8. Sorghum malt made at 30 degrees C had higher alpha -glucosidase activities than the corresponding malts made at 20 degree s C and 25 degrees C. Nevertheless, the sorghum malts made at 20 degre es C and 25 degrees C produced worts which contained more glucose than worts of malt made at 30 degrees C. Although barley malts contained m ore alpha-glucosidase activity than sorghum malts, the worts of barley had the lowest levels of glucose. The limitation to maltose productio n in sorghum worts, produced at 65 degrees C, is due to inadequate gel atinization of starch and not to limitation to beta-amylase and alpha- amylase activities. Gelatinization of the starch granules of sorghum m alt in the decantation mashing procedure resulted in the production of sorghum worts which contained high levels of maltose, especially when sorghum malt was produced at 30 degrees C. Although the beta-amylase and alpha-amylase levels of barley malt was significantly higher than those of sorghum masted optimally at 30 degrees C, sorghum worts conta ined higher levels of glucose and equivalent levels of maltose to thos e of barley malt. It would appear that the individual activities of al pha-glucosidase, alpha-amylase and beta-amylase of sorghum malts or ba rley malts do not correlate with the sugar profile of the correspondin g worts. In consequence, specifications for enzymes such as alpha-amyl ase and beta-amylase in malt is best set at a range of values rather t han as single values.