In recent years, the number of patients with diabetes or obesity has increased rapidly, and the glycemic index (GI) of grains has attracted attention. Using GI value to guide the choice of grains is of great significance to the prevention and control of chronic diseases such as diabetes. However, the GI value of grains is influenced significantly by processing methods and is often directly related to measurement methods. Therefore, this paper summarizes the current methods used to determine the GI value of foods as well as their advantages and disadvantages. Thereafter, this review also analyzes the effects of different processing methods on the GI values of grains and their products, and explains the possible mechanism for changes in the GI value of grains from the perspective of the interaction between various components in grains caused by processing methods. This paper is expected to provide an effective basis for the prediction of changes in the GI value of grains and the selection of processing methods, and also provide a reference for the research and development of grain products with low GI value.

The structure and physicochemical properties of fermented wheat starch-guar gum (FS-GG) mixtures of wheat starch naturally fermented for 72 h and different proportions of GG (0%, 0.1%, 0.3% and 0.5%, m/m) were studied. The results showed that the addition of GG significantly reduced the amount of leached amylose and the swelling power of FS, and distinctly lowered its peak viscosity and setback value. GG resulted in aggregation of FS granules to form a gel with a tight network structure, and led to an overall increase in the storage modulus (G’) and loss tangent (tanδ). Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results indicated that the addition of GG reduced the degree of order, gelatinization enthalpy and relative crystallinity of FS. The gel firmness of FS-GG mixtures increased slowly during storage. The results of this study indicated that GG delayed the retrogradation of FS by changing its crystal structure and gel structure, and the effect was most pronounced at an addition level of 0.5% GG.