Abstract:

In this research, effects of proteases (bromelain, papain and alcalase) on microrheological characteristics of
soymilk gel were explored. The results showed that all three proteases had the capacity to coagulate soybean milk, while
the curding capacity of alacase was weak. At the early stage of curding, the MVI (macro viscosity index) of bromelainsoybean
milk system was higher, while the MVI values of different systems became similar with prolonging reaction time.
Temperature in the range of 30–70 ℃ played an important role in EI (elasticity index) of soymilk gel systems containing
different proteases. The EI of gel systems induced by bormelain or papain addition showed an enhancing trend with
increasing temperature to reach the maximum level of 0.002 34 and 0.002 75 nm-2, respectively, but temperature did not
obviously affect the EI of soymilk system added with alaclase. The curding capacity of bromelain increased to the maximum
level of EI at 800 U/mL followed by a decrease with increasing protease dosage in the range of 200–1 200 U/mL. Papain
showed an increased curding capacity as its dosage increased, while alcalase showed a downward trend.

Key words: protease, soybean milk, gel, microrheological characteristics, elasticity index