Abstract: A rheometer was used to measure the rheological properties of three fermented dairy products, which were made of milk, soybean milk and both of them, respectively. The results showed that all three kinds of fermented dairy products were thixotropic fluid with a hysteresis loop area ratio of 1: 0.56: 0.69 and a viscosity index ratio of 1: 0.63: 0.91. Under the conditions of constant temperature and rotate speed, the initial apparent viscosity ratio was 1: 0.99: 1.28. The slowest decrease rate of apparent viscosity was observed in fermented soybean milk. In strain sweep experiments, fermented soybean milk was found to be the most stable, followed by fermented milk and complex fermented milk. In temperature sweep experiments, fermented soybean milk had the strongest tolerance to temperature and fermented complex milk had maximum apparent viscosity. By comparing their rheological properties, fermented soybean milk revealed the strongest stability and the highest apparent viscosity. Complex fermented milk had a higher apparent viscosity and a higher stability than single fermented milk.

Key words: fermented milk, rheology, thixotropy, apparent viscosity