A new method for predicting the shelf life of milk powder based on the global stability index (GSI) theory was established. Under the accelerated storage conditions at different constant temperatures (20, 30, 40 and 50 ℃), changes in sensory quality, vitamin C content, hydroxymethyl furfural (HMF) content and water activity were monitored for the purpose of establishing the shelf life prediction model. Results demonstrated that the calculated values of GSI were satisfactorily fitted to a zero-order kinetic model. The activation energy and the pre-exponential constant were 49.47 kJ/mol and 4 474 924, respectively. The absolute value of relative error between the predicted and observed GSI values was within 20%. The product shelf life at 20, 30, 40 and 50 ℃ was calculated to be 147.5, 75.5, 40.3 and 22.4 d, respectively. The established model could effectively predict the shelf life of milk powder at storage temperatures in the range of 20 to 50 ℃.

A rapid method using helicase-dependent isothermal DNA amplification (HDA) for the detection of Gluconobacter in fermented milk was established. The ITS gene sequence (gene number KF896260.1) of Gluconobacter was selected as the target gene for design of specific primers, and the concentrations of UvrD helicase and T4 gp32 in the reaction system were optimized to establish an optimal reaction system. The HDA method was used to directly detect Gluconobacter in fermented milk. The established HDA system was used to amplify and electrophoretically detect various strains in fermented milk to verify the specificity of the method and determine its detection limit. The results showed that the detection of Gluconobacter in fermented milk by the HDA method was consistent with the designed sequence length (309 bp) and the detection limit was 4.3 × 101 CFU/g. The appropriate amounts of UvrD helicase and T4 gp32 added in the reaction system were 0.1 and 5.0 μg, respectively. The method is highly sensitive and time saving.

An analytical method for the determination of 4 steroid hormones in milk and milk power was developed by filtration solid phase extraction combined with ultra performance liquid chromatography-tandem mass spectrometry. Samples were extracted with acetonitrile, and purified on a PRiME HLB cartridge. Then the chromatographic separation was achieved using an Acquity BEH C18 column (2.1 mm × 100 mm, 2.5 μm) with a mobile phase consisting of water and acetonitrile. The compounds were ionized using an electrospray ionization source in the negative ion mode and quantitated by the internal standard method. The results showed that the calibration curves of all analytes had a good linear relationship in the concentration range of 0.2–100.0 ng/mL. The limits of detection and limits of quantitation were 0.4–2.0 and 0.8–4.0 μg/kg, respectively. The recoveries of the method were in range of 87.7%–110.8% with relative standard deviations (RSDs) of 0.85%–4.56% in milk and in range of 89.2%–107.4% with RSDs of 0.85%–4.56% in milk power. This method was proved to be rapid, sensitive, and useful for the quantification of 4 steroid hormones in milk and milk power samples.

In recent years, with the growth of dairy consumption, dairy quality and safety have become a matter concerning people’s health and safety. However, poisoning incidents often occurred because of dairy products contaminated by enterotoxin-producing strains of Staphylococcus aureus. Thus risk assessment of Staphylococcus aureus is important for raw milk as the source of dairy products. Based on the principles and guidelines of the Codex Alimentarius Commission for microbial risk assessment, this paper reviews the studies in the field of risk assessment of Staphylococcus aureus in raw milk, including hazard identification, hazard characterization, exposure assessment and risk characterization. Through the mature cases of quantitative risk assessment, we introduce the basic framework for quantitative risk assessment of Staphylococcus aureus in raw milk and propose that more intensive studies are needed to construct a prediction model of enterotoxin and that systematic monitoring and microbial risk assessment of raw milk from pasture to table is necessary for providing basic information for safety monitoring and early warning security system of raw milk and dairy products.

Objective: A loop-mediated isothermal amplification (LAMP) assay was designed for rapid and accurate detection of Bacillus cereus in yogurt. Methods: Two pairs of oligonucleotide primers exclusively amplifying the hblA gene of Bacillus cereus were designed and Bacillus cereus could be directly detected by LAMP in yogurt, and the amplification products were detected by electrophoresis. Results: Detection of Bacillus cereus in yogurt by the LAMP assay was highly specific, the sensitivity was 6.4 CFU/mL, and the detection limit was 21 CFU/mL. Conclusion: The LAMP was fast, sensitive and useful for the detection of Bacillus cereus in yogurt.

Yak milk is a rare source of milk with high nutritional value and is richer in protein than cow milk. This paper reviews the protein composition and nutritional and functional properties of yak milk as well as minor bioactive proteins and their functionalities aiming to provide useful guidelines for further research and development of yak milk.