Rheological properties of hot pepper-soybean paste

Rheological properties of fermented hot pepper-soybean paste (HPSP) were evaluated at different total solid contents (TS, 43.6-54.7%) and temperatures (10-40C). HPSP samples at 20C are highly shear thinning fluids (n=0.25-0.33) with large magnitudes of Casson yield stresses (106-573 Pa). Consistency index (K) and apparent viscosity (eta (a,20)) increased with increase in TS. Apparent viscosity of HPSP obeyed the Arrhenius temperature relationship. The magnitudes of activation energy (7.6-20.4 kJ/mole) for HPSP increased with increase in TS. A single equation, combining the effects of temperature and concentration on eta (a,20), was used to describe flow behavior of HPSP. The time-dependent model of Weltman was found to be most applicable (R-2 = 0.97-0.99) for HPSP. Storage (G') and loss (G ") moduli increased with increase in TS, while complex viscosity (eta*) decreased. Magnitudes of G' were higher than those of G " over the entire range of frequencies (omega).