Development of a rapid assessment method for the glycaemic index

Abstract

The glycaemic index (GI) is a measurement used to classify foods according to their potential for raising blood glucose levels. The GI of a foodstuff is generally measured by determining the increment in blood glucose concentration after the consumption of a test meal over a set period of time and comparing it with an isoglucosidic control meal (normally white bread or glucose) and expressed as a percentage within a group of individuals (in vivo). Rapid analysis methods (in vitro) are being developed and evaluated worldwide, and in many cases the values obtained have correlated well with the GI values determined by in vivo methods. The criticism against rapid analysis methods is that the methods do not provide numerical GI values. Proposed labelling legislation in South Africa recommends that suppliers should only indicate if the product has a high, intermediate or low GI. The purpose of this study was to investigate existing rapid assessment methods for the prediction of GI, and develop such a method for South Africa to be used by food producers as a screening tool during product development in line with the newly proposed national labelling requirements. The preliminary studies on the developed rapid assessment method indicated good repeatability (CV 0.78%), reproducibility and precision (CV 3.5%). Further comparative trials indicated that the in vitro method accurately predicts the GI category of Almera potatoes (Solanum Tuberosum L. cultivar Almera) and Gero fat free litchi and raspberry flavoured yoghurt, in line with results found from in vivo analysis. Significant inter-laboratory variability of in vivo analysis of GI values obtained for the Almera potato cultivar was found, and the need for future alignment of methodology and sample preparation is recommended./p>