氯化钙添加量对地衣芽孢杆菌凝乳酶凝乳性能的影响

凝乳酶是生产干酪中极为关键的酶制剂。在凝乳酶作用过程中,添加适量的氯化钙可缩短凝乳时间,增加凝块硬度,减少生产成本,对干酪品质的影响至关重要。本研究利用从甘肃省天祝藏族自治县牦牛牧区土壤中筛选得到的一株高效产凝乳酶的地衣芽孢杆菌菌株D3.11,优化培养后得到凝乳酶,通过分析凝乳过程中相关指标的变化规律、观察比较凝块的微观结构,研究氯化钙添加量对该酶凝乳性能的影响。结果表明,当氯化钙添加量为0.014%~0.022%时,地衣芽孢杆菌D3.11凝乳酶体系的黏度值随凝乳时间的延长先增大后保持稳定;地衣芽孢杆菌D3.11凝乳酶体系和商品酶体系的浊度值均随Ca²⁺浓度的增大而显著增大(P<0.05);地衣芽孢杆菌D3.11凝乳酶体系的粒径主峰分布在136.9~246.7 μm范围内,且粒径值在氯化钙添加量为0.020%时最大;流变学特性分析结果表明,地衣芽孢杆菌D3.11凝乳酶体系达到储能模量G'峰值的时间随氯化钙添加量的增加而缩短;两种酶体系的持水力在氯化钙添加量为0.014%~0.022%范围内显著增大(P<0.05),乳清OD值在氯化钙添加量为0.016%~0.022%范围内变化均不显著(P>0.05);通过激光扫描共聚焦显微镜观察凝块微观结构发现,随着氯化钙添加量的增加,两种酶体系中蛋白微粒均凝结得更紧密。本研究结果为细菌凝乳酶在干酪生产中的应用提供了理论依据。

Effect of CaCl2 Addition on the Coagulant Performance of Rennet From Bacillus licheniformis

Rennet plays an important role in cheese production. The addition of CaCl₂ could is shorten the coagulating time, increase the hardness of clot and reduce the production cost, which is vital during cheese ripening. In this paper, a type of rennet with higher thermal stability was obtained from Bacillus licheniformis D3.11, which was screened from the soil of yak pastoral area in Tianzhu Tibetan Autonomous County, Gansu Province. The production conditions of this rennet were also optimized. Effect of CaCl₂ addition on the performance of the enzyme was analyzed with the change rules of related indexes in the process of milk coagulation. Skimmed milk was used as substrate and commercial rennet as control. The results showed that the viscosity of the two rennet systems increased firstly and remained stable with the prolonging of coagulation time when the CaCl₂ condition was within the range of 0.014%~0.022%. The turbidity values of the two rennet systems were significantly increased with the increase of CaCl₂ condition (P<0.05). The rheological properties showed that the time of the two rennet systems reaching the peak value of storage modulus G' was shortened with the increase of Ca²⁺ concentration. The water retention capacity of the two rennet systems was significantly increased in the range of 0.014%~0.022% CaCl₂ condition (P<0.05), while the whey OD value had no significant change within the range of 0.016%~0.022% CaCl₂ (P>0.05). By laser confocal microscope observation, the protein aggregation presented by the two rennet systems condensed more closely with the increase of CaCl₂ condition. This study provides a technique basis for the application of rennet from Bacillus licheniformis D3.11 for cheese processing.