ABSTRACT. In order to evaluate the milk yield, milk quality, and health of dairy cows fed a high-concentrate (HC) diet, eight lactating Holstein dairy cattle were randomly assigned to HC or low-concentrate (LC) diet groups and fed for 50 days, and the autocontrol studying before and after treatment with the two diets was used. During the experiment, plasma and milk samples were collected and measured. With regard to milk component, HC feeding led to higher milk production (P < 0.05), but significantly lower milk protein percentage (P < 0.05), milk protein yield (P < 0.05), and milk fat percentage (P < 0.05) throughout the five periods than LC feeding. Milk somatic cell count and N-acetyl-D-glucosaminidase activity (P < 0.01) were higher than those observed under LC feeding. mRNA expression levels of interleukin-8 (IL-8), C-C motif chemokine ligand (CCL5), and lactalbumin alpha (a-LA) were investigated by qPCR and found to be significantly lower (P < 0.01) in cattle fed the HC diet. The amino acid content was analyzed by high performance liquid chromatography (HPLC), and the content of Asp (P < 0.01), Gln (P < 0.01), Ala (P < 0.05), Leu (P < 0.05), Lys (P < 0.05), and Ile (P < 0.01) was significantly lower in the HC group, whereas the content of Arg (P < 0.05) and Phe (P < 0.01) was significantly higher. These results suggest that the HC diet might have an important influence on mammary health. The amino acid content was lower, suggesting that depletion of amino acids, resulting in depleted milk protein, affects milk quality.

Staphylococcus aureus is a common foodborne pathogen that is ubiquitous in nature. Consumption of contaminated foods, such as dairy products, can lead to food poisoning caused by heat-stable staphylococcal toxins that are not easily destroyed during pasteurization. The objective of this study was to investigate the growth kinetics of S. aureus and background microorganisms in camel milk stored at different temperatures between 8 and 43°C using one-step kinetic analysis to estimate the kinetic parameters from the observed growth curves. The growth of S. aureus showed apparent lag, exponential, and stationary phases, whereas no or negligible lag phase was observed for background microorganisms. Data analysis showed that the estimated minimum, optimum, and maximum growth temperatures were 5.9, 42.0, and 49.2°C for S. aureus, and 3.0, 38.6, and 49.2°C for the background microorganisms, respectively. The estimated optimum specific growth rate was higher for S. aureus (1.24 h −1 ) than for background microorganisms (0.995 h −1 ). This study found that camel milk may inhibit the growth of S. aureus, as it exhibits a lower specific growth rate than that in cow milk or cooked potato. It also has a longer lag phase than that in cow milk at comparable temperature ranges. This unique property is probably related to the presence of some antimicrobial compounds naturally occurring in camel milk. Validation of kinetic parameters and models showed that the root mean square error of prediction was only 0.5 log cfu/mL for S. aureus and background microorganisms, suggesting that the models are reasonably accurate. These models can be used for conducting risk assessments of S. aureus and predicting the general microbiological shelf life of camel milk to prevent foodborne staphylococcal poisoning.

Glutinous rice tea wine is an alcoholic beverage with antioxidant function which has good market value. However, it is prone to turbidity and precipitation during storage. To improve the unstable quality of glutinous rice tea wine, pectinase is used to clarify it. Based on single factor test and response surface test, the optimal clarification process parameters of pectinase, including pectinase addition, enzymolysis temperature, and enzymolysis time were optimised. Then, the antioxidant activity of glutinous rice tea wine was determined. Results showed that the effect of three clarification treatments on the clarification of glutinous rice tea wine was in the order of pectinase addition > enzymolysis temperature > enzymolysis time, and the optimal clarification conditions were: pectinase addition was 0.4 mL/L, enzymolysis temperature was 40.3°C, and enzymolysis time was 120.2 min. Under the optimal condition, the transmittance of glutinous rice tea wine was 92.3%, while the half maximal inhibitory concentration (IC50) of glutinous rice tea wine on the scavenging rates of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·), hydroxyl radical (·OH), and superoxide anion radical (O2-·) were 53.64, 41.18, and 66.56 mg/mL (ethanol content), respectively. Therefore, glutinous rice tea wine had certain antioxidant capacity and health promotion effect which provided a theoretical basis for improving the added value of medium- and low-grade teas.