An examination of the possibility of lowering the glycemic index of oat and barley flakes by minimal processing

Differences in glycemic responses to various starchy foods are related to d ifferences in the rate of starch digestion and absorption. In this study, t he importance of the degree of gelatinization and the product thickness for postprandial glycemic and insulinemic responses to rolled oats and barley were studied in healthy subjects (5 men and 5 women). Thick (1.0 mm) rolled oats were made from raw or preheated (roasted or steamed) kernels. In addi tion, thin (0.5 mm) rolled oats were made from roasted or roasted and steam ed (processed under conditions simulating commercial production) oat kernel s. Finally, steamed rolled barley kernels (0.5 or 1.0 mm) were prepared. Al l thin flakes elicited high glucose and insulin responses [glycemic index ( GI), 88-118; insulinemic index (II), 84-102], not significantly different f rom white wheat bread (P > 0.05). In contrast, all varieties of thick oat f lakes gave significantly lower metabolic responses (GI, 70-78; II, 58-77) t han the reference bread (P < 0.05). Thick barley flakes, however, gave high glucose and insulin responses (GI, 94; II, 84), probably because the botan ical structure underwent move destruction than the corresponding oat flakes . We conclude that minimal processing of oat and barley flakes had a relati vely minor effect on GI features compared with the more extensive commercia l processing. One exception was thick oat flakes, which in contrast to the corresponding barley flakes, had a low GI.