| Imitation cheeses are manufactured by blending various edible ingredients and water to form cheese-like products with the aid of heat and mechanical shear. The increase in demand of natural cheese as a primary ingredient of fast food has not only caused difficulties in supply, but also increased the cost of the product. Thus, imitation cheeses are widely used because of their cost-effectiveness, the simplicity of their manufacture and the replacement of selected milk by non-dairy fats or proteins. The feasibility of the small-scale imitation cheese making method was studied using a rapid visco analyzer (RVA), and the key factors involving processing parameters and raw materials which influence the quality of imitation cheese were investigated, which would lay a foundation of developing imitation cheeses in our country. The results are as follows:1. The method of a small-scale (30 g) analysis was investigated using a rapid visco analyzer (RVA). The data for time of emulsification, hot apparent viscosity and end apparent viscosity during RVA manufacture were collected, which were correlated with each other. There were no significant differences in the characteristic values between the imitation cheeses made by RVA, which also showed a good correlation with the characteristic values of imitation cheese using a batch system. Additionally, adjustments in the RVA method indicated a uniform protein matrix; the functional properties of the imitation cheese made by the RVA treatments had no significant differences with the control through comparing the texture and microstructure.2. The melt properties of imitation cheeses were analyzed by the RVA, tube melt test and texture profile analysis (TPA) hardness. There was a good correlation between the data collected during RVA melt analysis. The result of this study indicated that RVA melt analysis of imitation cheese was correlated with the results of tube melt test. The RVA hot apparent viscosity had a high correlation (R2 = 0.9529) with tube melt length. The RVA melt analysis could be used to evaluate the melting characteristics of imitation cheese.3. In this study, the effects of heating temperature, stirring speed and heating time on the quality properties of imitation cheese were investigated. Increasing the heating temperature, the hardness and hot apparent viscosity were increased before 85℃and then decreased subsequently. The hardness, hot apparent viscosity and free-oil release were increasing with the increase of stirring speed. When the heating time was extended, the values of hardness, hot apparent viscosity and free-oil release also increased firstly and then decreased stably. The mathematical model on the sensory evaluation was studied by three factors quadratic rotation design. The parameters of optimum processing conditions in the continuous production for imitation mozzarella cheese were heating time 85.57℃, stirring speed 451.46 r/min and heating time 7.50 min.4. The work was also to study the influence of raw materials on the properties of imitation cheese. (1) According to one factor design of emulsifying salts, the pH values decreased and hot apparent viscosities increased respectively when phosphates were added, and the pH values increased while hot apparent viscosities increased at first and decreased subsequently when sodium citrate were added. When the proportion of the two different emulsifying salts was 5:1, the mixture of sodium citrate and disodium hydrogen phosphate was the optimum. (2) With the increase of water, the hardness, hot apparent viscosity and springiness decreased significantly (P < 0.05); with the increase of soybean oil, the hardness, hot apparent and springiness all increased at first and decreased subsequently; with the increase of sodium chloride, the hardness and hot apparent viscosity increased significantly, while pH value decreased significantly; with the increase of citric acid, the hardness and hot apparent viscosity increased significantly, which had a direct relationship with the decrease of pH. (3) On the base of one factor design which has four factors (water, soybean oil, sodium chloride and citric acid), a mathematical model was set up whose response values were hardness, adhesiveness, springiness and cohesiveness. Consequently, the hardness and adhesiveness were directly influenced by the contents of water, soybean oil, sodium chloride and citric acid, while the springiness was affected by oil and citric acid, and the cohesiveness was strongly influenced by soybean oil, sodium chloride and citric acid. The optimum conditions for imitation mozzarella cheese were water 48.88 %, soybean oil 24.36 %, and sodium chloride 2.11 %, citric acid 0.73 %.5. The new imitation cheeses containing soy protein isolate or potato starch were developed. Mathematical model was studied by response surface methodology with the addition of protein substitution, heating speed and stirring speed. The experiments showed that optimum conditions for sensory acceptance of imitation cheese were the addition of soy protein isolate 4.3 %, heating temperature 91℃and stirring speed 460 r/min, and the addition of potato starch 5.2 %, heating temperature 86.7℃and stirring speed 502 r/min.
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