An ultra-high performance liquid chromatography (HPLC) method was established for the determination of the content of citric acid in dairy products. The samples were precipitated by K3Fe(CN)6 and (CH3COO)2Zn, extracted ultrasonically, and cryogenically centrifuged to precipitate protein and fat. The chromatographic separation was accomplished on a Poroshell 120 Aq-C18 column (4.6 mm × 100 mm, 2.7 μm) using gradient elution with a mobile phase consisting of a mixture of methanol and ammonium dihydrogen phosphate solution. The analyte was detected by an ultraviolet (UV) detector and quantified by the external standard method. The results showed that the calibration curve was linear with a correlation coefficient above 0.999 9. The average recovery from spiked samples was 95.3%–104.8%, the detection limit was 100 mg/kg, and the relative standard deviation (RSD) for precision was 0.16%–2.41%. The method is simple and rapid and has good separation effect. It is suitable for the quantitative analysis of citric acid in milk and dairy products.

An analytical method was established for the determination of the residues of 11 sulfonamides and five quinolones in infant formula milk powder using ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS). Acidified acetonitrile was used for sample extraction and the extract was purified and concentrated by solid phase extraction (SPE) using a PRiME hydrophilic lipophilic balance (HLB) column, then separated on an XBridge BEH C18 column, detected in the positive ion mode using an electrospray ionization source, and quantified by the calibration curve method with matrix matching. The calibration curves of all analytes showed a good linear relationship in the concentration range of 2–100 ng/mL with correlation coefficients greater than 0.995 0. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1-0.2 and 0.3-0.5 μg/kg, respectively. Recoveries for spiked samples were between 84.8% and 108.0%, with relative standard deviations (RSDs) between 0.36% and 5.41%. The proposed method is simple, efficient, reliable and sensitive.

In order to provide users of goat milk powder with its nutritional information and, more broadly, to promote the goat milk industry’s development, this study designed and constructed a nutrition information management system for goat milk powder based on browser/server (B/S) architecture and the MySQL database using Java as the primary system development language and the front-end and back-end separation technology as well as deploying microservice architecture using the Docker platform. This system consisted of four functional modules: system management, data upload and addition, quick query and special topic analysis, which allowed rapid and accurate search of various nutritional ingredients of goat milk powder, obtaining of the quality differences of different types and regions of goat milk powder, and preliminary identification of the geographical origin of goat milk powder. This information management system is simple, widely applicable, and helpful for quality control and improvement of goat milk powder, and provides data guarantee for safe consumption of goat milk powder.

To identify and test the quality of commercial goat milk powder sold in different areas, reversed-phase high performance liquid chromatography (RP-HPLC) was used to determine the protein composition of 35 samples of pure and formulated goat milk powder purchased in different regions (Shaanxi and non-Shaanxi) of China and in other countries, and the difference in protein composition among goat milk powder from different production areas and that between pure and formulated goat milk powder were analyzed. The results showed that the contents of αs2-casein and β-casein in formulated milk powder were 20% and 24% lower than those in pure milk powder, respectively, and the contents of κ-casein and whey proteins were 30% and 50% higher than those in pure milk powder, respectively. However, the protein composition and content of pure goat milk powder from different regions were similar. Therefore, RP-HPLC is useful for protein quality evaluation of commercial goat milk powder.

A liquid chromatographic (LC) method was established for the determination of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in ultra high temperature (UHT) milk. The proteins in milk were denatured by adding a buffer solution containing bis[tris(hydroxymethyl)aminomethane (BisTris), guanidine hydrochloride, sodium citrate, dithiothreitol, etc. The analytes were detected by an ultraviolet (UV) detector and quantified by the external standard method. The results showed that the calibration curve of each protein had good linearity with a correlation coefficient above 0.995. The recoveries of spiked samples were between 95.2% and 105.0%, the detection limit was 0.01–0.02 g/100 mL, and the relative standard deviation was 0.78%–2.70%. The method is characterized by good separation effect, good repeatability and simple operation, and is suitable for quantitative analysis of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in UHT milk.

A beverage stabilizer consisting of a mixture of xanthan gum,carboxy methyl cellulose (CMC) and propylene glycol alginate (PGA) at a ratio of 1 ∶ 1.5 ∶ 6.25 was developed by one-factor-at-a-time method and used in a dairy beverage supplemented taking mung bean protein as one of the ingredients.The formulation of the beverage was optimized by orthogonal array design for improved sensory evaluation and emulsion stability.Meanwhile,the thermal stability of the product was evaluated.The optimal formulation was found to consist of 8.0％ whole milk powder,1.0％ mung bean protein,10.0％ white sugar,0.4％ stabilizer and 0.3％ citric acid.The resulting product had a rich milky aroma and delicate taste with moderate sweetness,and its emulsion stability was 98.60％.The milk protein content was 1.95％,which was in line with the national standard requirements of GB/T 21732-2008 for milk beverages.

The formulation of donkey hide glue containing aqueous from edible flowers and skim goat milk was optimized using combination of one-factor-at-a-time method and response surface methodology with Box-Behnken design.The response variables were sensory evaluation scores and gel strength.The results showed that the optimum formulation was composed of 62.4％ skim goat milk,6.2％ donkey hide glue,aqueous flower extract 14.9％,and 0.075％ composite gelling agent.The resultant product showed a sensory score of 9.6 and a gel strength of 35.8 g.Physicochemical analysis indicated that the product contained ≥ 6.80 g of protein and ≤4.00 g of fat per 100 g of sample and thus could nourish blood and maintain beauty as a high-protein,low-fat product.

As an enzyme that catalyzes the transfer of acyl groups, transglutaminase is widely used in the dairy industry. This paper briefly describes the source and catalytic mechanism of the enzyme, and further explains the mechanism of action of the enzyme on milk proteins, including casein, whey protein and milk protein products. Moreover, the application of the enzyme in the dairy industry is summarized in this paper.