Binding of aromatic compounds with soy protein isolate in an aqueous model: Effect of pH

Interactions of the flavoring compounds hexyl acetate (HxAc), heptyl acetate (HpAc), linalyl formate (LiFo), linalyl acetate (LiAc), geraniol, linalool, limonene, and myrcene with soy protein isolate (SPI) were estimated in pH 3.0, 6.0, and 9.0 aqueous solutions using headspace solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). The binding capacity of HxAc, HpAc, LiFo, LiAc, geraniol, and linalool increased in the pH of the medium from 3 to 9. For limonene and myrcene, an unexpected increase in headspace concentration or a "salting-out" effect was observed. Between pH 3 and 9, better accessibility to the primary hydrophobic sites as a result of a modification to the protein's flexibility was observed. PRACTICAL APPLICATIONS: SPME method is a technology of dynamic adsorption for flavors. The lowest level of lead be practicably detected in food as low as the practiced concentration of flavors (0.01-0.1 mM) in our study. At low concentrations of flavors, it is close to the actual flavor's concentration of food. In the previous studies, the technology, such as equilibrium dialysis, headspace-gas phase which need higher concentration of flavors (>0.2 mM). The interaction between flavors and protein has a different binding law at high and low concentrations. As we produced the acid fruit soy protein milk beverage, the off-flavors present in the beverage were due to the change in the interaction between denature SPI and flavors. The present work is aimed at paving the way for further research to elucidate flavor imbalances in acid fruit soy protein milk beverage.

Can stevioside in combination with a soy-based dietary supplement be a new useful treatment of type 2 diabetes? An in vivo study in the diabetic goto-kakizaki rat

The diterpene glycoside stevioside (SVS) and soy bean protein isolate have both been shown to have beneficial effects in diabetes treatment. As they each show different benefits we investigated whether the combination of both substances shows an improvement in the treatment of diabetes in Goto-Kakizaki (GK) rats. Over the course of 4 wk, the rats were fed with the following four test diets (n = 12 per group): 1. Standard carbohydrate-rich laboratory diet (chow), 2. chow + SVS (0.03 g/kg BW/day), 3. 80% SPI + 20% chow and 4. 80% SPI + 20 % chow + SVS (0.03 g/kg BW/day). At the end of the course conscious rats underwent an intra-arterial glucose tolerance test (IAGTT) (2.0 g glucose/kg BW). Compared to normal chow diet, stevioside in combination with SPI shows the following beneficial effects in GK rats with mild type 2 diabetes: 1. a 56% reduction in plasma glucose (p < 0.001), 2. a 118% increase in first-phase insulin (p < 0.005), 3. a 20% reduction in glucagons (p < 0.05), 4. a 28% reduction in total cholesterol (p < 0.001), 5. a 13% reduction in FFA (p < 0.01), 6. a 49% reduction in TG (p < 0.001) and 7. a 11% reduction in the systolic blood pressure (p < 0.001). In conclusion, the combination of stevioside and SPI has synergistic positive effects on the characteristic features of the metabolic syndrome, i.e. hyperglycemia, hypertension and dyslipidemia.