Pulses are gaining ground as a useful source of nutrients in the diet, due to their high protein, starch, fibre and vitamin and mineral content, and low fat content. They have been studied for their role in weight management, have a low glycaemic index, and may be helpful in the management and prevention of diseases like diabetes and coronary heart disease. However the new study conducted by researchers in Canada highlights the vast differences that can occur both in the digestion of pulse flours between species and between cultivars of the same species, and their functional (gelatinizing and pasting). Such differences need to be taken into account when a pulse is being considered for its food use, or applications in an industrial setting. The authors of the new study, which has been accepted for publication in the journal Food Chemistry, noted that most of the studies on the composition and physiochemical properties of pulse flour have used a single cultivar or different cultivars in the same species. In these cases, it can be hard to know whether the pulses have been grown under the same environmental conditions - an important point when it comes to comparing properties because the growing conditions can affect properties. Since thermal and pasting properties, and nutritional fractions are all important when it comes to using pulse flours in food, the Canadian research team, set out to investigate some pea, lentil and chickpea cultivars that have only recently been introduced. These were grown in Canada under identical conditions, in the same location in Saskatchewan, Canada. This was intended to provide a level playing field for comparison between lentil, pea and chickpea, and the different cultivars. The study The researchers obtained three pea cultivars (1674-13, 1215-33, and 1329-12), two lentil cultivars (CDC Meteor and CDC Robin), and three chickpea cultivars (Myles, FLIP 97-101C and 97-Indian2-11). The whole pea, lentil and chickpea seeds were then milled to flour without being de-hulled. The researchers conducted assays on their chemical composition (moisture, protein, apparent amylose, total starch, and lipid contents); swelling power; amylose leaching; gelatinization properties; pasting properties; in vitro starch digestibility and expected glycaemic index. They reported that the lentil flour had higher protein content and higher gelatinization transition temperatures than the pea and chickpea flours - factors that may explain why it had the lowest expected glycaemic index of the three, and was hydrolysed more slowly and to a lesser extent than the pea and chickpea flours. The chickpea flour, on the other hand, showed lower amylose content and lower protein content, which could explain the higher expected glycaemic index and starch digestibility. "The difference in starch digestibility of pulse flours of the same species could be associated with differences in chemical compositions and physicochemical properties, due to inherent genetic differences," concluded the researchers. And it was in the chickpea flours that the more significant differences were observed between cultivars with respect to swelling power, gelatinization, pasting. Source Food Chemistry (online ahead of print) DOI: 10.1016/j.foodchem.2008.03.062 "In vitro starch digestibility, expected glycemic index, and thermal and pasting properties of flours from pea, lentil and chick pea cultivars." Authors: Hyun-Jung Chung, Qiang Liu, Ratnojothi Hoover, TomWarkentin, Bert Vandenberg
