可溶性大豆多糖与果胶对酸化乳饮料的稳定机制对比

Comparison of Stabilization Mechanism of Acidified Milk Beverage Stabilized by Soluble Soybean Polysaccharides and Pectin

摘要:

酸性乳饮料存在乳蛋白沉淀和乳清析出的问题，需要添加果胶等多糖作为稳定剂。可溶性大豆多糖（SPSS）具有黏度低、溶解性好和口感清爽等优点，但其稳定酸性乳饮料的机制尚不明确。作者以脱脂乳为主要原料的调酸型和发酵型酸性乳饮料为研究对象，通过测定LUMiSizer不稳定指数、SEC-HPLC（分子体积排阻高效液相色谱法）表征的复合物形成量、粒径、ζ-电位及冷藏14 d贮藏稳定性等指标，对比研究SPSS与果胶稳定酸化脱脂乳、酪蛋白和乳清蛋白等3种乳蛋白体系的机制差异。结果显示，对于3种直接酸化的乳蛋白体系，2 g/L的SSPS无法与酪蛋白形成有效复合物并稳定体系，2 g/L果胶对3种乳蛋白均无法有效形成复合物且不能良好稳定体系，其余质量浓度的多糖均能与3种10 g/L乳蛋白形成复合物，并且冷藏14 d贮藏稳定性良好。对于发酵脱脂乳，只有添加6 g/L果胶时才能被有效稳定。乳清蛋白和酪蛋白的稳定性结果并不能预测发酵脱脂乳的稳定效果。平均粒径结果显示，3种直接酸化的乳蛋白体系的粒径均远小于发酵酸化体系；增加SSPS添加量无法有效降低发酵脱脂乳的平均粒径，但对于直接酸化的3种乳蛋白体系、发酵酸化乳清蛋白和酪蛋白，随着SSPS添加量的增加，平均粒径都显著下降；果胶降低酸化乳蛋白粒径的能力远不如SSPS。上述结果说明，酸化乳蛋白的粒径是影响多糖复合物形成的要素之一，在复合物有效生成的前提下，体系黏度可能也是影响体系稳定性的重要因素。离心稳定性不能表征长期存放稳定性。对于直接酸化的乳蛋白体系，复合物形成量和平均粒径可能对于预测长期存放稳定性更有意义；对于发酵酸化的乳蛋白体系，平均粒径和黏度可能对于预测长期存放稳定性更有价值。

Abstract:

There are problems in acidified milk beverage including protein precipitation and whey isolation, and polysaccharides such as pectin are often used as stabilizers. Soluble soybean polysaccharide(SSPS) has low viscosity, good solubility and refreshing taste, however, its stabilization mechanism of acidified milk beverage is still unclear. Acidified milk beverage processed by formulation and fermentation with skim milk was studied, and the differences of mechanism between SSPS and pectin stabilizing three kinds of acidified milk proteins (skim milk, casein and whey protein) were investigated by the LUMiSizer instability index, the complex content quantified by SEC-HPLC, the particle size, ζ potential and the 14-day cold storage stability. The results showed that for three acidified milk proteins processed by formulation, 2 g/L SSPS could not form effective complex with casein and stabilize acidified casein, and 2 g/L pectin could not form complex with 3 kinds of acidified milk proteins and failed to stabilize these milk proteins. SSPS and pectin under other mass concentrations could form complexes with three acidified milk proteins of 10 g/L, and showed good stability during 14-day cold storage. The fermented acidified skimmed milk could only be effectively stabilized by 6 g/L pectin. The stability tests of whey protein and casein could not predict the stability of fermented acidified skim milk beverage. The results of average particle size showed that the particle size of formulated acidified milk beverage was far smaller than that of the fermented acidified milk. The increasing of SSPS could not effectively reduce the average particle size of fermented skim milk. However, for three kinds of formulated acidified milk proteins and fermented acid whey protein or casein, the average particle size decreased significantly with the increasing of SSPS. The ability of pectin to reduce the particle size of acidified milk proteins was not as good as that of SSPS. These results indicated that the particle size of acidified milk protein was one of the factors affecting the formation of polysaccharide complex. Besides, the viscosity of milk beverage might also be an important factor affecting the stability of milk beverage if the complexes effectively formed. The long-term storage stability could not be characterized by centrifugation stability. For formulated acidified milk proteins, the complex amount and average particle size might be more important for predicting the long-term storage stability, while for fermented acidified milk proteins, the average particle size and viscosity might be more useful.