ABSTRACT
The aim of this work was to optimise a soybean/cornstarch extrudate by adjusting a central composite design and to maximise a product with a high protein and resistant starch (RS) content by evaluating the indigestible fractions through in vitro colonic fermentation and production of short-chain fatty acids (SCFAs) with potential health benefits. According to the response surface analysis and RS maximisation results, an optimisation of the independent variables was obtained as follows: 32.5% feed moisture, 144 °C extrusion temperature and a proportion of 44% germinated soybean flour and 56% cornstarch. A product with a 2.11% expansion index, 6.25 N hardness, a glycaemic index of 49 and 12% resistant starch was obtained. The optimised extrudate showed a 36% indigestible fraction and high fermentability with respect to that of the lactulose control. Furthermore, the decrease in pH was inversely proportional to the production of SCFAs and the volume of gas generated. Acetic, propionic, and butyric acids were produced at a molar ratio of 62:27:11, while the highest SCFA concentrations were found 48 h after incubation. The RS of the optimised extruder was a viable substrate for in vitro colonic fermentation, suggesting that it is a good food source to produce SCFAs, which could exert an effect on the regulation of lipid and glucose metabolism.
ABSTRACT
The aim of this study was to analyzing the impact of germination time on the morphology, crystallinity, gelatinization and viscosity properties on the starch of Esmeralda and Perla barley variety. The two barley were germinated for 1 to 8â¯days, at 26⯰C and 65% relative humidity. Micrographs showed the presence of pinholes and eroded surfaces. Starch in Esmeralda was hydrolyzed completely at 8â¯days of germination. Birefringence was reduced from day 4, losing molecular structuring of the crystalline area. Morphometric data: fractal dimension, area, perimeter, circularity, and roundness decreased significantly along germination time in both varieties. The entropy increased significantly, from 0.79 to 10.09 in Esmeralda and from 0.46 to 7.57 in Perla. Relative crystallinity decreased significantly in the Perla from 24.7% to 23.6%. Viscosity peaks were also significantly reduced, pasting temperature was constant in Esmeralda but in Perla was significantly reduced from 95.43 to 95.19⯰C with germination, the gelatinization temperature increased significantly in the Esmeralda while in Perla it remained constant. Enthalpy decreased significantly to 75.8% and 37% in Esmeralda and Perla respectively. The study of germination impact on structural and physicochemical properties is important to identify the use of hydrolyzed starches in the food industry or others.
