| The soft ice cream premix powder is a convenient raw material for ice cream making that attracting broad consumers which meets the requirements of “produced on site”, “made while selling” and “home-made”. However, it is necessary to replace the non-dairy creamer with natural healthy plant oil which can improve the nutrition of soft ice cream premix powder as a higher demand for people to choose high quality and nutrient soft ice cream product. Moreover, Palm mid fraction(PMF) as a by-product of palm oil was paid more attention to the application in food production gradually, and showed excellent features. Thus, in this paper, the PMF was applied in the producing of soft ice cream premix powder. PMF can be used for the producing of soft ice cream premix powder by analyzing and comparing the physical and chemical properties, fatty acid composition(FAC) and solid fat content(SFC) of PMF and the oils extracted from representative commercial soft ice cream premix powders. And the effects of different amounts of emulsifiers and PMF on physicochemical properties, rheological, thermodynamic property and particle size distribution of PMF based soft ice cream were also studied. On the basis of above research, an optimum preparation formula of PMF based soft ice cream premix powder was established on an expectation to lay a preliminary technical reference for industrial production. The main research and results are as follows:(1) The melting point, iodine value fatty acid composition(FAC)and solid fat content(SFC) were comparative analyzed between the oil extracted from four commercial soft ice cream premix powders and six PMFs. The results showed that the SFC of PMF with melting point of 37.2 oC(PMF) had an extremely curves similar to the oil extracted from commercial soft ice cream premix powders. And the SFC of PMF changed slowly with the temperature increased from 0oC to 10oC and from 26.7oC to 33.3oC, while decreased rapidly with the temperature increased from 10oC to 26.7oC than other PMFs. Meanwhile, the ratio of saturated fatty acid and unsaturated fatty acids in PMF-3 was close to 1∶1, and the main fatty acid in PMF is palmitic acid.(2) The effects of sucrose fatty acid ester(SE-13) and glyceryl monostearate(GMS) on the physicochemical properties, rheological property, thermodynamic property and particle size distribution of PMF based soft ice cream were investigated by several methods. Results showed the fat globule aggregation degree of PMF based soft ice cream was reduced with the increasing of a moderate amount of emulsifier, while the viscosity, overrun value and melting resistance significantly improved, including the melting point of fat crystals. However, SE-13 had a larger influence on the apparent viscosity of PMF based soft ice cream than GMS, but the GMS performed a larger influence on slurry pseudo plastic than SE-13. Besides, the melting point of ice crystals of mixed system was decreased by adding a derisory or excessive amounts of SE-13, but the utilization of GMS significantly increased the melting point of ice crystal.(3) The most appropriate ratio of PMF was 10% by analyzing the effects of different amounts of PMF on the physicochemical properties of soft ice cream. Orthogonal test indicated the optimum proportion of stabilizers was: 0.10% guar gum, 0.05% xanthan gum, 0.20% CMC and 0.04% carrageenan. Sensory evaluation showed the optimum formulation was: 8.00% PMF, 8.00% skim milk powder, 1.00% maltodextrin and 12.00% granulated sugar.(4) The physicochemical properties of two PMF based soft ice cream premix powder prepared by spray freeze drying and spray drying were comparative analyzed. The product premix powder prepared by spray freeze drying performed a significant improvement in solubility and emulsification stability than that prepared by spray drying, while the latter exhibited a better oil length and density properties. Compared with the commercial soft ice cream, the cost of PMF based soft ice cream premix powder decreased by 31.46%. Sensory evaluation showed the product made by PMF based soft ice cream premix powder performed a similar quality and acceptability, and had more advantages on overrun values and melting resistance. |
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