Starch and its nutritional quality.
A. H. M. LIN (1), B. R. Hamaker (2). (1) Bi-State School of Food Science, University of Idaho and Washington State University, Moscow, ID, U.S.A.; (2) Whistler Center for Carbohydrate Research, Dept. Food Science, Purdue University, West Lafayette, IN, U.S.A.
Dietary carbohydrates are important in providing energy to humans, but carbohydrates are increasingly thought of as "bad" foods associated with obesity, diabetics and associated chronic symptoms. The objective of this report is in regard to how moderating glucose delivery profiles might be done to affect physiologic endpoints that may address these public health problems. To generate absorbable glucose, digestion of starch requires two types of digestive enzymes: α-amylase and mucosal α-glucosidase. α-Amylase hydrolysis affects the rate of oligomer generation, and mucosal α-glucosidase digestion directly influences the rate of glucose generation. Our research has shown that mucosal α-glucosidase carries an unexpectedly high digestive capacity, and it digests α-amylase hydrolyzates obtained from different botanical sourced starches in different manners. Thus, in a significant way controls dietary glucose generation. Susceptibility to mucosal α-glucosidase depends in part on the architecture of internal amylopectin molecules with long chains correlating to slower starch digestion. These findings lead us to propose that dietary glucose can be continuously and slowly (sustainably) released by mucosal α-glucosidase digestion. Several projects were conducted to examine how the slowly released dietary glucose may contribute to humans. Alginate-based microspheres embedded with starch were developed to deposit glucose at different rates in the small intestine and glucosidase activity, synthesis, feeding behavior, hypothalamic neuropeptides, and gastric emptying were examined in rat and mouse models. Our results showed that relatively small amount of dietary glucose delivered distally appears to create certain same and second meal physiological effects including modulation of gastric emptying rate of nutrients for digestion and absorption into the body, and reduced food intake accompanied by a lowering of the orexigenic neuropeptides of the hypothalamus. Our findings lead us to propose a new concept that dietary glucose is a bioactive molecule as it triggers physiological response, in addition to its major energy providing role, and mucosal α-glucosidase serves as a gatekeeper that controls the released of the glucose. Overall, a goal in future research is to develop food technologies, as well as to identify practical approaches, using whole grain or whole foods, or mixtures of food ingredients and whole foods, for such carbohydrate quality health-related effects.
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