The effects of heat sterilization and microwave sterilization on the stability and casein structure of fresh camel milk were compared. The microwave sterilization conditions were optimized using single factor experiments and response surface methodology based on Box-Behnken design. Changes in the structure and properties of camel milk casein after sterilization were investigated using a differential scanning calorimeter, a Fourier transform infrared spectrometer, and a scanning electron microscope. The centrifugal sedimentation rate of protein and the total number of colonies were taken as response variables, the optimum conditions were determined as follows: pH 7.0, microwave power 560 W and microwave irradiation time 120 s. After microwave treatment under these conditions, the centrifugal sedimentation rate of protein was 6.96%, and no bacterial colonies were detected. Differential scanning calorimetry (DSC) plot showed that microwave treatment resulted in higher enthalpy of camel milk casein compared with heat sterilization, indicating a lower degree of denaturation and higher stability. The results of scanning electron microscopy showed that both sterilization methods destroyed the micellar structure of casein to varying degrees, resulting in cross-linking and aggregation. However, after microwave sterilization, the casein showed ordered aggregation, forming small aggregates that assembled into an ordered network structure. Appropriately increasing the pH of camel milk before sterilization was conducive to its stability. Different sterilization methods had a significant effect on the secondary structure of camel milk casein. Both microwave and heat sterilization reduced the relative contents of α-helix and β-turn in the casein. The relative content of β-sheet in heat-sterilized camel milk casein was the highest, indicating the most significant change in the secondary structure of the protein. In summary, this study revealed the stability of camel milk and the structural change of camel milk casein under different sterilization conditions, which can help address the poor stability of thermally sterilized camel milk at this stage.

The regulatory effect of yak ghee sphingomyelin on lipid metabolism disorder and liver inflammation in high-fatdiet (HFD)-fed mice was investigated. Thirty C57 BL/6J male mice were randomly divided into five groups: low-fat control, high-fat, high-dose sphingomyelin (1.20 g/100 g ), medium-dose sphingomyelin (0.60 g/100 g) and low-dose sphingomyelin (0.30 g/100 g). Serum lipid levels were measured using commercially available kits, and the expression levels of lipid metabolism factors such as 3-hydroxy-3-methylglutarate coenzyme A reductase (HMGCR) and stearoyl-coenzyme A desaturase 1 (SCD1), and inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in liver tissues of each group were determined by enzyme-linked immunoassay (ELISA) and fluorescence quantitative polymerase chain reaction (PCR). The results showed that yak ghee sphingomyelin reduced serum total cholesterol, triglycerides and low-density lipoprotein cholesterol levels in HFD-fed mice (P < 0.05). The greatest decrease in the total cholesterol, triglycerides, low-density lipoprotein cholesterol and blood sugar levels was observed in the high-dose sphingomyelin group, by 26.26%, 24.70%, 38.96% and 42.16%, respectively. In addition, the expression levels of the HMGCR and SCD1 genes (P < 0.05) were significantly up-regulated and the pro-inflammatory cytokines TNF-α and IL-6 (P < 0.05) in liver tissue were down-regulated by sphingomyelin compared to the high-fat group. Consequently, yak ghee sphingomyelin can improve lipid metabolism disorders caused by HFD and prevent the occurrence of liver inflammation.

Brown adipose tissue (BAT) improves the metabolic level of the body by promoting energy expenditure, which can contribute to the prevention and treatment of metabolic diseases such as obesity and diabetes, and BAT has become a new target for the treatment of metabolic diseases. BAT activity enhancement in the body is a hot topic but also a challenge for researchers, and research and analysis of functionally active factors in foods that regulate BAT can help to develop new nutritional activators. In this paper, we summarize the development and thermogenesis of BAT and thermogenesis-related factors, and review active ingredients in foods that regulate brown fat and their mechanisms of action, and briefly introduce the effects of white adipose tissue (WAT) and BAT on the body’s health. We also discuss recent developments in understanding the role of BAT in regulating energy metabolic balance and various diseases in the body. We hope that the present review will provide a theoretical basis for future development of brown adipose nutritional activators and improvement of individualized healthy dietary management programs in order to prevent and treat various diseases.

To solve the difficulty of storing and transporting yak butter, yak butter microcapsule powders were prepared using a mixture of maltodextrin and sodium caseinate as the wall material, a mixture of molecular distilled monoglycerides and sucrose ester as the emulsifier and guar gum as the stabilizer by vacuum freeze-drying or spray drying. The basic physicochemical properties (moisture content, solubility, rheology, surface oil content, encapsulation efficiency, and yield), microscopic structure, and thermal stability of the two as-prepared samples were compared. The results showed that the microencapsulated powders prepared by the two methods were milky white in color and free of impurities, and had a fresh aroma. Both of them exhibited high encapsulation efficiency, (90.17 ± 1.07)% and (92.12 ± 0.32)%, respectively. The yield of freeze-dried microcapsule powders, (98.42 ± 0.38)%, was significantly higher than that of spray-dried microcapsule powders, (25.77 ± 1.34)%, and the average particle size (D_[4,3] = 16.695 μm) was smaller than that of spray-dried powder (D_[4,3] = 24.945 μm). The solubility and fluidity of the spray-dried powder were superior to those of the freeze-dried powder. Under a scanning electron microscope (SEM), the surface of spray-dried powder was smooth and spherical in shape, while the freeze-dried powder was irregular. The thermal stability of the spray-dried powder was better. In summary, when considering economic benefits, the spray-dried powder holds greater significance for industrial production.