Approaches to reduce the glycemic response of gluten-free products: in vivo and in vitro studies.

This article aims to discuss the current approaches used to reduce the postprandial glycemic response (GR) of starchy gluten-free products (GFP) and to provide some further prospects. The GR is evaluated through in vivo trials to determine the glycemic index (GI) and the glycemic load (GL) of foods or using the in vitro starch digestibility method to predict the GI. The reviewed studies demonstrated that a reduction in the GR of GFP can be achieved by replacing traditionally used refined flours and starches with nutrient-dense alternative raw materials due to an increase in dietary fiber, resistant starch and protein contents, which can alter the rate of starch digestion, reduce the GI and dilute the amount of available carbohydrate; both the factors contribute to reduce the GL. The addition of viscous dietary fibers could also be a successful way to reduce the GR of GFP. Some studies have demonstrated the potential of germination of GF grains and sourdough fermentation in decreasing the GR of GF bread. Further studies could evaluate alternative GF flours, soluble fibers, resistant starch, and other formulation factors that may affect the GR of different types of GFP. New studies should be performed to test and optimize processing methods by considering the reduction of GR of GFP. Another key aspect for further investigation is the confirmation of the promising results obtained through in vitro assays by in vivo GI evaluation.

Effects of processing methods on amaranth starch digestibility and predicted glycemic index.

Amaranth has attracted a great deal of interest in recent decades due to its valuable nutritional, functional, and agricultural characteristics. Amaranth seeds can be cooked, popped, roasted, flaked, or extruded for consumption. This study compared the in vitro starch digestibility of processed amaranth seeds to that of white bread. Raw seeds yielded rapidly digestible starch content (RDS) of 30.7% db and predicted glycemic index (pGI) of 87.2, the lowest among the studied products. Cooked, extruded, and popped amaranth seeds had starch digestibility similar to that of white bread (92.4, 91.2, and 101.3, respectively), while flaked and roasted seeds generated a slightly increased glycemic response (106.0 and 105.8, respectively). Cooking and extrusion did not alter the RDS contents of the seeds. No significant differences were observed among popped, flaked, and roasted RDS contents (38.0%, 46.3%, and 42.9%, respectively), which were all lower than RDS content of bread (51.1%). Amaranth seed is a high glycemic food most likely because of its small starch granule size, low resistant starch content (< 1%), and tendency to completely lose its crystalline and granular starch structure during those heat treatments.