Effect of incorporating legume flour into semolina spaghetti on its cooking quality and glycaemic impact measured in vitro.

Spaghetti is a favoured carbohydrate source because of its low glycaemic impact. The protein quality of semolina spaghetti is not ideal, however, and could be improved by including legume flour. We investigated whether incorporating legume flour in spaghetti, to improve its nutritional value, would affect its cooking quality and glycaemic impact. Four types of spaghetti containing 10% of either mung bean, soya bean, red lentil or chickpea flour were made and compared with a spaghetti control made only of durum semolina. Cooking quality was determined as the optimal cooking time (OCT), cooking loss (CL), dry matter (DM), swelling index, colour, hardness and adhesiveness. The spaghetti samples with legume flour were similar to one another and to the control in values of OCT, DM, swelling index, colour, CL, hardness and adhesiveness. Glycaemic impact of the samples was measured in vitro as release of rapidly available carbohydrate and slowly available carbohydrate during pancreatic digestion. The glycaemic index (GI) of the spaghetti samples was estimated by calculation, using data obtained for a reference food of known GI (shredded wheat horizontal line an extrusion-cooked wheat-only product). The shredded wheat underwent rapid parabolic digestion, and the near linear phase during which most of the starch was digested was completed between 20 and 60 min digestion. In contrast, the digestion of spaghetti was much slower and progressed almost linearly to completion. All spaghetti samples, moreover, were similarly susceptible to digestion, and compared with the wheat reference were all significantly lower in terms of relative glycaemic impact. We conclude that the incorporation of 10% legume flour in spaghetti to improve its nutritional value does not affect its cooking quality or increase its glycaemic impact.