Abstract: Nutritional powders with various carbohydrates (corn syrup solids, isomaltulose, crystalline fructose, maltitol, tapioca dextrin, resistant dextrin, and oligofructose) added were prepared using concentrated whey protein powder and plant fat powder as the main raw materials. The effects of the type and content of carbohydrates on the in vitro digestion characteristics and expected glycemic index (eGI) of nutritional powders were investigated. On this basis, the relationship between different carbohydrates and eGI was explored using the logarithm of slope (LOS) model and the combination of parallel and sequential (CPS) model, and a glycemic index (GI) prediction model was constructed. The results showed that crystalline fructose, maltitol, and oligofructose significantly reduced the eGI of nutritional powders by decreasing the rate and degree of hydrolysis during digestion (P < 0.05). In contrast, tapioca dextrin and corn syrup solids increased the hydrolysis rate during the fast digestion stage, leading to a higher eGI, whereas isomaltulose did not affect the eGI (P > 0.05). Meanwhile, LOS and CPS analysis showed that all carbohydrate combinations except those at low levels of corn syrup solids or tapioca dextrin exhibited a mixed digestion pattern with sequential/parallel kinetics. Finally, a prediction model for GI was established as follows: GI = 46.347 + 0.142 × isomaltulose − 0.925 × crystalline fructose − 3.004 × maltitol + 2.090 × corn syrup solids + 1.406 × tapioca dextrin – 0.054 × resistant dextrin – 1.555 × oligofructose. The results provide a theoretical basis for the formulation design and nutritional evaluation of nutritional powders.

Key words: in vitro digestion; glycemic index; nutritional powders; functional sweeteners; soluble dietary fiber