In the processing of dairy products, heat treatment is usually used to ensure food safety and extend product shelf life. Being advantageous over thermal processing, ultra-high pressure, a non-thermal processing technology that kills or inhibits contaminating microorganisms in milk, can not only ensure the safety of dairy products and extend the shelf life, but also can have an impact on the sensory quality, nutrient retention and processing properties of milk proteins. In this paper, the recent progress in the effects of ultra-high pressure treatment on the sensory, physicochemical and protein processing properties of milk is reviewed, which will provide a rationale for the application of ultra-high pressure in dairy processing.

High hydrostatic pressure (HHP) is considered one of the most sustainable and green technologies. HHP can prolong the shelf life of food, change the physical and chemical properties of milk proteins and enzymes, and improve the functions, nutritional characteristics and sensory quality of food. In this paper, the structural and functional changes of proteins and enzymes in milk caused by HHP treatment are reviewed, which provides a rationale for the application of high hydrostatic pressure in dairy products.

The objective of this paper was to optimize the fermentation conditions of lactose-free yogurt. The level of residual sugar was used as response variable. Moreover, lactose-free yogurt and ordinary were prepared under the same conditions and their sensory characteristics were compared. Also, differences in their instrumental quality characteristics were assessed using an electronic eye, an electronic nose and an electronic tongue. The results showed that the optimal fermentation conditions were as follows: lactase dose 3.9 U/L, inoculum size 2 U/1 000 kg, fermentation temperature 43 ℃ and time 5.5 h. The lactose content of the yogurt prepared under the optimized conditions was (0.29 ± 0.07) g/100 mL. The lactose-free yogurt showed a 1.5-fold increase in lactic acid bacterial count than the ordinary yogurt (P < 0.05), but there was no significant difference in acidity or viscosity between them (P > 0.05). Principal component analysis (PCA) demonstrated no significant difference (P > 0.05) in color, aroma or taste. Therefore, compared with the ordinary yogurt, the lactose-free yogurt had no significant difference in sensory quality.