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Dietary fibre and low glycaemic index cereal foods Ongoing research at CCFRA may facilitate the development of starchy products with a low glycaemic index (GI). GI is a measure of how quickly foods that contain carbohydrate raise blood glucose levels. Medical studies have indicated that rapid and large elevations of blood glucose may have long-term negative effects on health. A low GI diet may be effective in the prevention and management of a number of chronic diseases (e.g diabetes and cardiovascular disease). Incorporation of certain dietary fibres can lower the GI of a food product. The interactions between different dietary fibres and the main food components during various processing stages are being investigated. Model systems as well as foods are being used to evaluate the effect of dietary fibres on rheological characteristics, water distribution between individual components, starch retrogradation, storage characteristics and in vitro starch digestibility. 
An in vitro method for evaluating starch digestibility has been developed. It involves simulated mastication and multi-enzymic digestion based on a proteolytic stage, followed by incubation with pancreatic a-amylase restricted by dialysis tubing. This method allows the calculation of a hydrolysis index (HI) and a predictive GI for each test sample, thus ranking carbohydrate rich foods based on their rate of starch digestibility. This is a much more convenient and rapid method than in vivo testing, which involves feeding the trial food to human volunteers and measuring blood glucose levels over time and comparing these with the effects of a standard product (usually white bread or glucose) on the same subjects. Although the in vitro method can only give an approximate GI value, this is likely to still be very valuable to product developers, when trying to formulate reduced GI foods. Contact: Anton Alldrick |