Production of Cowpea Miso: Effect of Fermentation Time on Its Rheological Properties

Miso is a fermented food produced using soybeans, often consumed in the Japanese diet. In this study, an innovative miso was produced by fermenting cowpea instead of soybean. The effect of fermentation time on the rheological proprieties of miso throughout its production was evaluated. Cowpea miso fermented for 1 month and for 6 months were compared in terms of texture and linear viscoelastic behaviour. The results showed that over 5 months, the firmness and adhesiveness of the miso decreased significantly. The mechanical spectra revealed that the miso behaviour remained predominantly elastic: elastic modulus (Gʹ) higher than viscous modulus (Gʺ) with less than a decade apart, showing slight dependence of frequency. Despite the decrease in Gʹ and Gʺ, there was no reduction of the complexity of the internal structure of the miso: the Plateau modulus (G0N) did not decrease significantly. Over the next few months of fermentation, G0N is expected to decrease in line with miso firmness.