Variation in total and soluble beta-glucan content in hulless barley: Effects of thermal, physical, and enzymic treatments

Total and soluble beta-glucan content and effects of various treatments of barley grain on extractability and molecular characteristics of soluble bet a-glucan were studied. Four types of hulless barley (normal, high amylose, waxy, and zero amylose waxy) from 29 registered and experimental genotypes were analyzed. For each, moisture, protein, amylose, 100 kernel weight, sta rch, beta-glucan (total and soluble), beta-glucanase activity, and slurry v iscosity were determined. Significant differences in total beta-glucan were observed among the groups, with average values of 7.49%, 6.86%, 6.30%, and 4.38% for high amylose, waxy, zero amylose waxy, and normal barley, respec tively. The extractability of beta-glucan. in high amylose barley was relat ively low (20.6-29.7%) compared to that in normal (29.8-44.3%), zero amylos e waxy (34.0-52.5%), and waxy (36.7-52.7%) barley genotypes, Viscosity of b arley flour slurries was affected by the content of soluble beta-glucans, b eta-glucanase activity, and molecular weight of beta-glucans. Hydrothermal treatments (autoclaving and steaming) of barley had no effect on extractabi lity of beta-glucans, but prevented enzymic hydrolysis of beta-glucans, and thereby substantially improved their molecular weight. The addition of enz ymes (protease and esterase) during extraction and/or physical treatments ( sonication) increased extractability of beta-glucans from barley.