Selenium is an important trace mineral element, which plays an important role in animal physiological activities. Selenium-enriched probiotics can convert inorganic selenium into organic forms, promoting the absorption and utilization of selenium and in turn enhancing the antioxidant capacity and immunity of dairy animals, and can also increase the content of selenium in dairy products, thereby improving the nutritional value and quality of dairy products. In order to provide a reference for the development of dairy production in the future, this paper reviews the application of selenium-enriched probiotics in dairy production, discusses the effects of selenium-enriched probiotics on the production performance, milk yield and quality of dairy animals, and analyzes future development of selenium-enriched probiotics.

An ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) method was established for the determination of six quaternary ammonium disinfectant residues in milk-containing food for special medical purposes. The sample was extracted with 80% acetonitrile in water and the extract was separated on a RRHD Eclipse Plus C18 column, detected in the positive ion mode using an electrospray ionization source with multiple reaction monitoring (MRM), and quantified by matrix-matched standard calibration. The calibration curves for the six quaternary ammonium disinfectants was linear in the concentration range of 0.1–5.0 ng/mL with correlation coefficient higher than 0.996 0. The limit of detection (LOD) was 0.5 μg/kg and the limit of quantification (LOQ) was 1 μg/kg. The recoveries were 72.8%-102.3% for spiked solid matrix samples, and 71.8%–100.8% for spiked liquid matrix samples with relative standard deviations (RSDs) in the range of 0.25%–3.88% and 0.19%–2.51%, respectively. The proposed method is simple, efficient, rapid, sensitive, and suitable for the qualitative and quantitative analysis of quaternary ammonium disinfectant residues in food for special medical purposes.

In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine the contents of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and infant formula. The sample was dissolved with ultrapure water, and reacted with dithiothreitol and iodoacetamide to open disulfide bonds and simultaneously protect sulfhydryl groups before being hydrolyzed with trypsin. After completion of the reaction, aqueous acetonitrile was used for making up to a constant volume, and then centrifugation was carried out to take the supernatant for quantification by external standard method. The results showed that the calibration curves for all analytes were linear in the range of 0–100 μg/mL, with correlation coefficient (r) greater than 0.995. The average recoveries of the analytes from spiked raw milk were 93.5%–117.1%, with relative standard deviation (RSD) ranging from 1.4% to 6.7%. In conclusion, the method was simple, rapid and sensitive, and could be used for the determination of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and milk powder samples.

This study established a method for the simultaneous detection of 19 β-agonist veterinary drug residues in milk samples. The samples were extracted with acidified acetonitrile solution, and the phospholipids were removed by using an Oasis PRiME HLB solid-phase extraction cartridge. The analytes were detected by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Under optimized pretreatment and instrumental conditions, all analytes showed a good linear relationship in the concentration range of 0 to 10 ng/mL (R2 ≥ 0.995). The average recovery rates for milk samples spiked at levels of 0.2 to 1.0 μg/kg were between 70% and 110%, and the precision relative standard deviation (RSD) was less than 15%. The method had the advantages of simple and fast pretreatment, and high sensitivity and stability, and therefore could be used for the rapid detection of β-agonist veterinary drug residues in milk.

This paper describes a method for determination of vitamin K2 (menaquinone-7, MK-7) in milk powder using high performance liquid chromatography (HPLC). The sample was hydrolyzed with lipase (250 mg/g) for 2 h, saponified with potassium carbonate (500 mg/g), extracted with n-hexane, concentrated by rotary evaporation, reconstituted with methanol/isopropanol (4:1), and post-derivatized with C18 column and reduced column before being analyzed by HPLC with a fluorescence detector. The analyte was quantified by external standard method. The results showed that the peak of MK-7 appeared at about 19.47 min, and the calibration curve for it showed a good linear relationship in the range of 0.0–1.5 μg/mL (R2 = 0.999 95). The recoveries for blank samples spiked at 5, 10 and 25 μg/100 g were between 87.9% and 94.3%, with relative standard deviations of 0.9%–6.4%. When 2 g of sample was taken and the volume was made up to 1 mL, the detection limit was 0.15 μg/100 g and the quantification limit was 0.5 μg/100 g. The method was simple with high accuracy, sensitivity and stability, and could be used for the detection of vitamin K2 (MK-7) content in milk powder.

Ultra high performance liquid chromatography (UPLC) is a stable, easy-to-use, and selective analytical technology with variable sensitivity which is superior to high performance liquid chromatography in many aspects such as better chromatographic separation, more sensitive analysis, shorter analysis time and reduced solvent consumption. The application of UPLC in the rapid detection of dairy additives, food additives, contaminants, mycotoxins and illegal chemical additives is reviewed in this article.

The purpose of this investigation was to study the influence of adjuvant starter cultures on the quality of fermented milk. Seven strains of common lactic acid bacteria, including Lactococcus lactis subsp. cremoris (Lcr), Lactococcus lactis subsp. lactis (Ll), Lactobacillus casei (Lca), Lactobacillus fermentum (Lf), Lactobacillus rhamnosus (Lr), and two Lactobacillus plantarum strains (Lp1 and Lp2), were used separately as adjuvants to a commercial starter culture for fermented milk. The results showed that addition of adjuvant starter cultures could shorten the fermentation time and affect the pH value of fermented milk during storage. Moreover, Lcr and Ll could cause significant changes in the oxidationreduction potential during fermentation. Rheological measurements indicated that these strains could increase the viscosity, and reduce the elasticity and fluidity of fermented milk. The texture analysis showed that all the strains could increase the water-holding capacity, and Lr, Lf and Lp1 could enhance the cohesiveness and adhesiveness of fermented milk. Gas chromatography-mass spectrometry (GC-MS) analysis and principal component analysis showed that Lr, Lp1, Lp2 had little effect on the flavor of fermented milk, while Lca could promote the formation of heptanol, benzaldehyde and 2-tridecanone, and Lf, Ll and Lcr could increase the content of flavor substances such as short-chain and medium-chain fatty acids in fermented milk.

This experiment was conducted to investigate the effects of composite enzyme preparation FE907 on milk production and disease resistance of lactating dairy cows. A total of 28 lactating Holstein dairy cows were randomly allocated into two groups with 14 ones per group, which were fed a total mixed ration (TMR) alone and supplemented with 20 g/d·cow of FE907, respectively. The feeding experiment lasted four weeks. The results showed that the daily milk production was increased by 1.6 kg/d (P > 0.05) in response to dietary supplementation of FE907. In addition, an increase of 0.08% in the fat content of milk and of 0.09 kg/d in the production of milk was observed over the control group with significant differences (P < 0.05). The protein content of milk and the production of milk protein were also increased by 0.06% and 0.07 kg/d, respectively. The benefit per day from one cow was 6.28 RMB more than the control group. It is concluded that supplementing 20 g/d·cow of the enzyme preparation to the diet has a positive effect on improving the milk yield, milk composition and economic benefit while reducing the risk of developing mastitis.

Enzymatically modified cheese (EMC) is a kind of food ingredient with strong cheese flavor, produced by enzymatic hydrolysis of natural cheese at different ripening stages. As a kind of concentrated cheese flavor substance, EMC is being increasingly widely used to satisfy consumer demands in the food industry. This paper provides a systematic review on the recent progress in the research and development of EMC with respect to the production process, quality evaluation and flavor improvement. Furthermore, prospects and directions for its future development in China are presented.