Influence of Grain Processing on in vitro Enzymatic Starch Digestion of Barley and Sorghum Grain

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Abstract
Laboratory studies were conducted to determine in vitro enzymatic starch digestion of barley and sorghum grains, and to ascertain the influence of various grain processing methods on the starch availability of barley and sorghum grain to enzymatic degradation. In vitro starch digestion was determined by incubating ground samples of grain with porcine pancreatin or a homogenate of lyophilized bovine pancreas. At the conclusion of the 30-minute incubation period, starch digestion of eight samples of barley was higher than the average of 11 sorghum grain samples. Steaming or pressure cooking at 1.4 kg/cm2 for 1 minute without flaking decreased in vitro starch digestion of barley and sorghum grain as compared with the untreated grains. Starch digestion of pressure-cooked barley and sorghum grain was improved at steam pressures exceeding 2.8 kg/cm2. Flaking the grains after steaming or pressure cooking markedly increased in vitro digestion of both grains. Digestibility improved with increased degree of flaking (flake flatness). Similar results were obtained with both enzyme sources. These data suggest that the degree of flaking is the principal factor in the processing methods studied which influences availability of barley and sorghum grain starch to in vitro enzyme attack.