Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing 100048, China.
Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing 100048, China; Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology and Business University, Beijing 100048, China.
J Dairy Sci. 2019 Sep;102(9):7849-7862. doi: 10.3168/jds.2019-16305. Epub 2019 Jul 3.
We investigated the effect of low concentrations (0.1 to 1%, wt/wt) of gelatin (types A and B) on the properties of acid milk gels in terms of rheology, tribology, texture, and water-holding capacity to better understand the role of gelatin in yogurt. The 2 types of gelatin showed similar effects on the properties of milk gels, with some minor differences, such as lubrication behavior at low concentrations. During acidification, gelatin at ≤0.4% caused an increase in the gel strength, and at higher concentrations it showed a negative effect. However, during cooling and annealing, we observed a positive effect on gel strength with 0.8 and 1% gelatin. Gelling and melting occurred at 0.8 and 1% concentrations of both types of gelatin. The addition of gelatin tended to decrease the storage modulus of milk gels and increase the apparent viscosity, pseudoplasticity, consistency, and yield stress. The firmness of the gels was decreased by gelatin at medium concentrations, but increased at high concentrations. Gelatin significantly enhanced the water-holding capacity of the gels; we observed no serum at concentrations ≥0.4%. With the addition of gelatin at concentrations ≥0.4%, the particle size of gels was greatly reduced, and their lubrication properties were significantly improved. This study showed that 0.4% was an effective concentration in acid milk gel; above this concentration, the properties of the milk gels were greatly changed. Tribology provided important information for understanding the role of gelatin in milk gels.
我们研究了低浓度（0.1%至 1%，重量/重量）的明胶（A 型和 B 型）对酸乳凝胶性质的影响，包括流变学、摩擦学、质地和持水性，以便更好地理解明胶在酸奶中的作用。这两种类型的明胶对牛奶凝胶的性质有相似的影响，但也存在一些细微的差异，例如在低浓度下的润滑行为。在酸化过程中，明胶浓度≤0.4%会增加凝胶强度，而在较高浓度下则会产生负面影响。然而，在冷却和退火过程中，我们观察到 0.8%和 1%的明胶对凝胶强度有积极影响。凝胶和融化发生在这两种类型的明胶浓度为 0.8%和 1%时。明胶的添加往往会降低牛奶凝胶的储能模量，并增加表观粘度、假塑性、稠度和屈服应力。凝胶的硬度在中等浓度的明胶下降低，但在高浓度下增加。明胶显著提高了凝胶的持水能力；我们在浓度≥0.4%时观察不到血清。当明胶浓度≥0.4%时，凝胶的粒径大大减小，其润滑性能显著提高。本研究表明，0.4%是酸乳凝胶的有效浓度；在此浓度以上，牛奶凝胶的性质会发生很大变化。摩擦学为理解明胶在牛奶凝胶中的作用提供了重要信息。
