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SYNOPSISThe effects of heating temperature on gel properties and conformational changes were investigated in glycinin and (3-conglycinin gels using rheological and Fourier transform ir (FTIR) methods. Solutions of 15 w t % glycinin or /I-conglycinin in 35 mM phosphate buffer at pH 7.6 were heated at various temperatures for 30 min and rheological properties were measured at 20°C. The storage modulus G' as a function of frequency changed from a monotonical decrease with decreasing frequency to a plateau in the range from 0.0018 to 40 H z by heating at temperatures higher than 80°C for glycinin and 65°C for (3-conglycinin.A band at 1618 cm-' (associated with the (3-sheet Structure) on ir spectra increased with the formation of heat-induced gels. The value of the storage modulus G' correlated well with the increase in absorbance at 1618 cm-'. These results suggest that the formation of a @-sheet structure may be closely related to the value of the storage modulus G' for heatinduced gels in soybean proteins and that heat-induced gels of glycinin and P-conglycinin are formed by cross-links with intermolecular (3-sheet structures. 0 1994

SYNOPSISThe heat-induced gelation of P-conglycinin was investigated by dynamic viscoelastic measurements as a function of pH. At pH values below 5.5-6.0, the storage modulus G' rapidly increased with decreasing pH. The conformational states of both sols and gels of @-conglycinin were investigated by Fourier transform ir (FTIR) and by differential scanning calorimetry (DSC). The degree of protonation of the carboxyl groups of P-conglycinin, when examined by FTIR indicated that, as would be expected, the degree of protonation increased with decreasing pH below pH 6.0. DSC measurements suggest that 8-conglycinin tends toward thermal denaturation with decreasing pH (below pH 6.0). Second-derivative FTIR spectra for P-conglycinin gels show that a band at 1620 cm-' (associated with exposed &strands) develops with decreasing pH. The results suggest that P-conglycinin undergoes denaturation with increasing protonation of its carboxyl groups, resulting in an increase in the amount of exposed P-strands. The exposed P-strands then intermolecularly bond to form gel networks. This process is promoted with decreasing pH, and as a result, rigid gels form at acidic pH values.

Preheated soybean protein isolates (SPIs) were prepared from new soybean lines that have extremely different compositions of -conglycinin and glycinin by a typical method for manufacturing commercial SPI. The gelation properties of these SPIs were investigated by dynamic viscoelastic measurements. The storage modulus G′ of 12% SPI was measured at pH 7.0 when the temperature was increased from 30 to 80°C and then lowered to 20°C at 2°C/min. Gelation properties of the preheated SPI were different from those of the non-pre-heated SPI. In the absence of NaCl, an increase in the storage modulus G′ was observed for preheated -conglycinin-rich SPI and preheated control SPI, but not for preheated glycinin-rich SPI. On the other hand, in the presence of 2.5% NaCl, an increase in the storage modulus G′ was observed for all preheated SPIs in the order -conglycinin-rich SPI > control SPI > glycinin-rich SPI. These results suggest that -conglycinin plays an important role in the heat-induced gel formation of commercial SPI.

Cellulose nanofiber (CN) consumption with exercise could be a potential strategy to control obesity. Here, we studied the effects of CN supplementation and voluntary exercise on obesity and gut microbiota in high-fat diet (HFD)-fed mice. Consumption of CN increased voluntary wheel running activity. CN intake and exercise together suppressed the increase in body weight and fat mass, and improved glucose tolerance. The fecal gut microbiota was analyzed by sequencing 16S ribosomal RNA genes. Principal component analysis revealed a shift in the microbiota composition resulting from exercise, but not from CN supplementation. Erysipelotrichaceae and Rikenellaceae decreased with exercise. Exercise also increased Ruminococcaceae, whereas exercise and CN intake together increased Eubacteriaceae. These two families are butyrate producers. Exercise increased the amount of acetate in the cecum. These results suggest that CN consumption improves exercise performance and exerts anti-obesity effects by modulating the balance of the gut microbiota.