Abstract: In this study, the effect of using centrifugal or screw pumps to deliver cream at different temperatures for ultra-high temperature (UHT) sterilization on the physicochemical quality of cream was investigated. It turned out that delivering cream at 10 ℃ by a centrifugal pump caused fat aggregation and precipitation and significantly reduced viscosity compared to delivering it at 60 ℃ or by a screw pump. The particle size of cream delivered at 10 ℃ by the centrifugal pump was the largest and most uneven, and the particle size of cream delivered at 60 ℃ by the centrifugal pump, at 10 ℃ and 60 ℃ by the screw pump were close. The particle size of cream delivered at 60 ℃ by the centrifugal pump was the most homogeneous. The whipping rate and hardness of cream delivered at 60 ℃ by the two pumps were close to each other, while cream delivered at 10 ℃ by the screw pump had the lowest whipping rate. Cream delivered at 10 ℃ by the centrifugal pump could not be whipped even after being churned for a long time. There was a significant difference in the microstructure but not the fatty acid composition of the four cream samples. Fat globules in cream delivered at 60 ℃ were small and dense while those in cream delivered at 10 ℃ were large and sparse, indicating that cream at low temperature is prone to aggregation caused by shear, resulting in fat aggregation and affecting cream quality. This finding is consistent with the particle size results.

Key words: Key words: cream; centrifugal pump; screw pump; particle size; whipping rate; microstructure

摘要： 使用离心泵和螺杆泵在不同温度输送稀奶油进行超高温杀菌，研究其对稀奶油理化品质的影响。结果表明：10 ℃时使用离心泵（10L组）输送稀奶油，会导致其脂肪聚结、析出，黏度显著低于在60 ℃时输送或使用螺杆泵输送；10L组稀奶油粒径最大、最不均匀，60 ℃使用离心泵（60L组）、10 ℃使用螺杆泵（10R组）和60 ℃使用螺杆泵（60R组）稀奶油粒径接近，其中60L组稀奶油粒径最均匀；60R和60L组打发率和硬度接近，10R组打发率最低，10L组经过长时间搅打后依然无法被打发；不同组稀奶油脂肪酸成分没有显著差异，但微观结构差异显著，60 ℃经过泵输送的稀奶油脂肪球小而密，10 ℃经过泵输送的稀奶油脂肪球大而疏，说明低温状态下的稀奶油易受剪切而聚结，从而使脂肪析出、影响稀奶油质量，这与粒径结果相吻合。

关键词: 稀奶油；离心泵；螺杆泵；粒径；打发率；微观结构