Teagasc Food Research Centre Moorepark, Fermoy, Co. Cork, P61 C966, Ireland; School of Food and Nutritional Sciences, University College Cork, T12 YN60, Ireland; Western Dairy Center, Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan 84321.
School of Food and Nutritional Sciences, University College Cork, T12 YN60, Ireland.
J Dairy Sci. 2019 Jun;102(6):4989-5004. doi: 10.3168/jds.2018-15051. Epub 2019 Mar 28.
The effects of the independent variables protein concentration (4-6%), coagulum cut size (6-18 mm), and coagulation temperature (28-36°C) on curd moisture loss during in-vat stirring were investigated using response surface methodology. Milk (14 kg) in a cheese vat was rennet coagulated, cut, and stirred as per semihard cheesemaking conditions. During stirring, the moisture content of curd samples was determined every 10 min between 5 and 115 min after cutting. The moisture loss kinetics of curds cut to 6 mm followed a logarithmic trend, but the moisture loss of curds from larger cut sizes, 12 or 18 mm, showed a linear trend. Response surface modeling showed that curd moisture level was positively correlated with cut size and negatively correlated with milk protein level. However, coagulation temperature had a significant negative effect on curd moisture up to 45 min of stirring but not after 55 min (i.e., after cooking). It was shown that curds set at the lower temperature had a slower syneresis rate during the initial stirring compared with curds set at a higher temperature, which could be accelerated by reducing the cut size. This study shows that keeping a fixed cut size at increasing protein concentration decreased the level of curd moisture at a given time during stirring. Therefore, to obtain a uniform curd moisture content at a given stirring time at increasing protein levels, an increased coagulum cut size is required. It was also clear that breakage of the larger curd particles during initial stirring can also significantly influence the curd moisture loss kinetics. Both transmission and scanning electron micrographs of cooked curds (i.e., after 45 min of stirring) showed that the casein micelles were fused at a higher degree in curds coagulated at 36°C compared with 28°C, which confirmed that coagulation temperature causes a marked change in curd microstructure during the earlier stages of stirring. The present study showed the dynamics of curd moisture content during stirring when using protein-concentrated milk at various set temperatures and cut sizes. This provides the basis for achieving a desired curd moisture loss during cheese manufacture using protein-concentrated milk as a means of reducing the effect of seasonal variation in milk for cheesemaking.
使用响应面法研究了独立变量蛋白浓度（4-6%）、凝块切割尺寸（6-18mm）和凝固温度（28-36°C）对罐内搅拌过程中凝乳水分损失的影响。在奶酪罐中，将 14kg 牛奶按半硬质奶酪制作条件进行凝乳凝固、切割和搅拌。在搅拌过程中，在切割后 5-115min 每隔 10min 测定一次凝乳样品的水分含量。切割尺寸为 6mm 的凝乳水分损失遵循对数趋势，但切割尺寸为 12 或 18mm 的凝乳水分损失呈线性趋势。响应面模型表明，凝乳水分水平与切割尺寸呈正相关，与牛奶蛋白水平呈负相关。然而，凝固温度对搅拌 45min 内的凝乳水分有显著的负影响，但在 55min 后（即烹饪后）则没有。结果表明，与在较高温度下凝固的凝乳相比，在较低温度下凝固的凝乳在初始搅拌过程中具有较慢的排乳速度，通过减小切割尺寸可以加速这一过程。本研究表明，在给定搅拌时间内，随着蛋白浓度的增加，保持固定的切割尺寸会降低凝乳的水分含量。因此，为了在增加蛋白水平的情况下获得均匀的凝乳水分含量，需要增加凝块的切割尺寸。很明显，在初始搅拌过程中较大凝乳颗粒的破裂也会显著影响凝乳水分损失动力学。经烹饪的凝乳（即搅拌 45min 后）的透射和扫描电子显微镜照片显示，与 28°C 相比，在 36°C 下凝固的凝乳中，酪蛋白胶束的融合程度更高，这证实了凝固温度在搅拌的早期阶段会导致凝乳微观结构发生明显变化。本研究展示了在不同设定温度和切割尺寸下，使用高蛋白浓度牛奶搅拌时凝乳水分含量的变化动态。这为在奶酪生产中使用高蛋白浓度牛奶来实现所需的凝乳水分损失提供了基础，这是减少奶酪生产中牛奶季节性变化影响的一种手段。
