Digestive analysis of processing effects on the glycaemic impact of oats in vitro

Forty six lines of oats from a program of breeding for low glycaemic impact were assessed by in vitro digestive analysis that allowed for theoretical effects of homeostasis on blood glucose concentrations. The oats were steamed and rolled (“rolled oats”; RO), and a portion made into porridge (PO) before in vitro digestive analysis. Carbohydrate digestibility was much greater and more rapid for PO than RO after 20 min digestion (RO, 16.9 g/100 g; PO, 42.5 g/100g on a dry oats basis) but similar after 120 min digestion (43 g versus49.8 g), reflecting a high proportion of slowly digested starch in RO. Taking into account theoretical blood glucose disposal, RO was equivalent in glycaemic effect to 10.8 g of glucose and the PO to 17.5 g of glucose per 40 g serving (10.8 versus 17.5 g glucose equivalents). Based on published GI values, in vitro glycaemic analysis allowing for homeostasis provided realistic relative estimates of effects of processing on glycaemic properties of cereal foods.