Glucose and insulin responses in healthy men to barley bread with different levels of (1→3;1→4)-β-glucans;: predictions using fluidity measurements of in vitro enzyme digests

Bread products with three different levels (35, 50 and 75%) of the (1 -> 3; 1 -> 4)-beta-glucan rich barley genotype Prowashonupana (PW), 50% common barley (CB) or 100% white wheat, were given as a breakfast meal to 10 men and their postprandial blood glucose and insulin responses were measured. In addition, the viscosity of (1 -> 3; 1 -> 4)-beta-glucans isolated from the pw flours was measured, and the fluidity characteristics of the (1 -> 3; 1 -> 4)-beta-glucans in the bread products estimated in in vitro enzymatic digests prepared under conditions simulating those prevailing in the gastrointestinal tract. Bread containing 50 and 75% PW flour lowered the glycaemic index (GI) (40 and 48%, respectively) and insulinaemic index (II) (37 and 34%) compared with a white wheat reference bread (GI = 100; 11 = 100). A high correlation (r = 0.9782; P = 0.0007) was found between the fluidity index (FI) of the enzymatic digests and GI of all bread products (GI = 50.8 + 0.441 FI). The overall conclusions were that incorporation of (1 -> 3;1 -> 4)-beta-glucan rich barley in bread may lower its glycaemic and insulinaemic properties and that the metabolic response could be predicted by measuring the in vitro fluidity of bread digests. (c) 2005 Elsevier Ltd. All rights reserved.