Coagulation temperature affects the microstructure and composition of full fat Cheddar cheese

An understanding of coagulation and factors that affect cheese microstructure is important, as this microstructure influences cheese texture and flavour. Of particular importance to many producers is the loss of milk fat during the cheese-making process, which reduces the inherent value of the product. The aim of this study was to investigate the effect of coagulation temperature on the microstructure of gel, curd and cheese samples during the manufacture of full fat Cheddar cheese. The microstructure of the gel formed at 27 °C consisted of a fine interconnected protein network as compared to a coarse, irregular and more discontinuous protein network in gel formed at 36 °C. At a higher coagulation temperature (36 °C), the size of the casein micelle aggregates in the protein strands increased when observed using confocal laser scanning microscopy possibly due to increased hydrophobic and ionic interactions and the rearrangement of casein micelles. This characteristic microstructure observed in the gel was retained in the curd collected prior to whey draining and may be responsible for the increased loss of fat in the whey. The concentration of fat in dry matter in cheese prepared from cheese-milk coagulated at 27 °C and 30 °C was significantly (P < 0.05) higher than in cheese made from milk coagulated at 33 °C and 36 °C possibly due to the observed differences in microstructure and the direct effect of coagulation temperature on physical properties of the fat and the casein micelles. Our results suggest the need to control milk coagulation temperature, as this parameter may affect product microstructure and fat retention.凝乳温度对全脂切达干酪微观结构和组成的影响摘要 干酪的微观结构能够影响干酪的质地和风味, 因此了解影响干酪微观结构的因素是非常重要的。在干酪加工中脂肪的损失是许多种类干酪加工中存在的重要问题, 脂肪的损失会引起干酪内在性质的改变。本文目的是调查在全脂切达干酪生产中凝乳温度对凝胶、凝块和干酪微观结构的影响。研究表明, 在 27 °C 形成的凝胶是由微小的蛋白质相互连接成的网络结构, 而在 36 °C 形成的凝胶结构则是由粗糙的、不规则的蛋白质形成的不连续的蛋白网络结构。共聚焦激光扫描显微镜的观察发现在较高的凝乳温度 (36 °C) 下, 在蛋白链中酪蛋白胶束聚合体的尺寸增大, 原因是酪蛋白胶束表面疏水性和离子相互作用的增加以及酪蛋白胶束的重新组合。所形成的这种凝胶结构一直保持到排乳清之前, 这有可能是脂肪向乳清中流失量增加的原因。在 27 °C 和 30 °C 下凝乳后制备的干酪总固形物中脂肪的含量显著 (P < 0.05) 地高于在 33 °C 和 36 °C 下凝乳制备的干酪, 原因是前后两者形成的微观结构的不同, 以及凝乳温度对脂肪和酪蛋白胶束物理性质产生了影响。本研究结果说明, 在工业生产中很有必要控制凝乳温度, 因为其直接影响最终干酪产品的微观结构。