In this study, to understand the differences in quality between high-fat and regular yogurts, we compared the changes in viable bacterial counts, acidity, and textural characteristics between homemade high-fat and regular yogurts as well as commercial yogurt (two samples for each type of yogurt) during the shelf life. The results showed that the fat content (16.7% and 17.0%) and energy (731 and 721 kJ/100 g) of high-fat yogurt were significantly higher than those of regular yogurt, and the carbohydrate content (3.6% and 2.3%) was significantly lower than that of regular yogurt. High-fat yogurt possessed a strong fatty flavor and a thick texture. The acidity (90.62 and 91.15 °T) and viable bacterial count (9.15 and 8.95 (lg (CFU/mL))) of high-fat yogurt were lower than those of regular yogurt, whereas the hardness (22.45 and 26.15 g), adhesiveness (0.59 and 0.72 mJ) and chewiness (0.86 and 1.03 mJ) were higher than those of regular yogurt. Compared to commercial yogurt, the acidity of homemade yogurts is more stable, but basically the same viable bacterial count and textural characteristics. In conclusion, high-fat yogurt has lower carbohydrate content, acidity and viable bacterial count, and the high fat content not only imparts a fatty flavor to this yogurt but also improves its textural properties and stability.

An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantitative determination of fumonisin B1 (FB1), fumonisin B2 (FB2) and fumonisin B3 (FB3) residues in milk powder and milk has been established. The samples were extracted with methanol-acetic acid (98:2, V/V), diluted, cleaned up by immunoaffinity chromatography (IAC), and blown to dryness under nitrogen. The residue was re-dissolved and detected using an electrospray ionization source (EIS) in the positive ion mode with multiple reaction monitoring (MRM) and quantitative analysis was performed by the isotope-labeled internal standard method. The limit of quantification was 10 μg/kg for FB1, FB2 and FB3 in milk powder and milk. The recoveries at spiked concentration levels of 10–400 μg/kg were 92.8%–107.5%, with relative standard deviations (RSD) of 2.0%–4.3%. The matrix effects were 96.25%–122.84%. This method was characterized by short analysis time and was suitable for the determination of fumonisin residues in different dairy products.

The objective of this study was to establish a method for detecting the residue of dicamba in cow milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 0.5% formic acid in acetonitrile, and the extract was purified by sodium chloride salting out, and separated on an Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.01% formic acid aqueous solution. Identification and quantification were achieved using an electrospray ionization source in the negative ion mode with multiple reaction monitoring (MRM). Under optimized pretreatment and instrumental conditions, good linearity was observed in the concentration range of 5.0–250.0 μg/L with correlation coefficient (r) more than 0.999. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were 5 and 10 μg/kg, respectively. The recoveries of dicamba at spiked concentration levels of 10, 20 and 200 μg/kg were 104.3%, 101.5% and 96.2% with relative standard deviations (n = 6) of 3.0%, 2.0% and 1.5%, respectively. This method is simple, accurate, repeatable, and suitable for the rapid detection of dicamba in milk.

The yak is a rare animal that predominantly lives on the Qinghai-Tibet Plateau. The production volume of yak milk is low, but it is rich in nutrients, containing higher contents of protein, fat and lactose compared with Holstein milk, as well as abundant amounts of other nutrients. Furthermore, it is found that yak milk has anti-hypoxia, anti-fatigue and antioxidant activities, among other, which may be attributed to the unique habitat of yaks. In this article, the lactation performance of yaks, as well as the nutritional components and functional characteristics of yak milk is reviewed, with a view to providing a theoretical reference for the development and utilization of yak milk.

A method for the determination of nonylphenol in liquid milk by using ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed. Samples were extracted using acetonitrile as extraction solvent and the organic phase was separated from the aqueous phase by adding saturated sodium chloride solution. The analyte was cleaned up using a ProElut PAEs Glass solid-phase extraction catridge and then separated on a Waters ACQUITY UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) using gradient elution with 0.1% ammonia water-methanol as mobile phase. The detection was performed by negative electrospray ionization under the multiple reaction monitoring mode and the quantitation was carried out by an internal standard method. The results showed a good linear relationship (R2 > 0.990) in then range from 1 to 200 ng/mL. The limit of detection（LOD, RS/N = 3）was 2.0 μg/kg and the limit of quantitation (LOQ, RS/N = 10）was 5 μg/kg. The recovery rate of the method for spiked samples was between 74.8% and 111.5% with relative standard deviation of 3.3%-9.0%. In general, the method was accurate, simple and reproducible and exhibited low background inference and it was thus suitable for the analysis of nonylphenol in liquid milk.

Fresh Pleurotus nebrodensis was homogenized for use as an ingredient in the formulation of milk beverage. The effect of homogenization time on the particle size distribution of mushroom homogenate was investigated by a laser particle size analyzer. The formulation was optimized using response surface methodology. The independent variables were concentration and particle size of Pleurotus nebrodensis homogenate, composite stabilizer and skim milk powder. The stability of beverage was used as response variable. The composite stabilizer consisted of pectin, carboxy methyl cellulose (CMC) and monoglyceride with a ratio of 1.0:1.3:1.7 (m/m). Incorporation of 8% mushroom homogenate passing through a 100-mesh sieve, 0.3% composite stabilizer and 9% skim milk powder gave a homogenous product with a moderate sour and sweet taste and the best stability of (89.20 ± 0.41)%. Particle size analysis showed that the mean particle size of the beverage was (46.30 ± 0.51) μm and the particle size distribution was as follows: D (10)=11.78 μm, D (50) = 28.70 μm, and D (90) = 108.80 μm, which was significantly different from that of three commercial milk beverages. This beverage contained more protein ((2.46 ± 0.12)%) than commercial beverages and met the requirement of the national standard for milk beverage (GB/T 21732?2008). The beverage displayed both irregular particles and regular spherical particles with uniform size distribution and without particle aggregation as observed under microscopy and its particle size distribution was similar to that of commercial beverages.

Fermented okara with good processing suitability containing 13.4% soluble dietary fiber (SDF) was homogenized with a blender. After addition of other ingredients, the homogenate was formulated to produce a healthy high SDF milk beverage that was uniform and tasted good. Using one-factor-at-a-time method and response surface methodology, the optimum homogenization conditions were determined as follows: blender treatment time 15 min, blender rotation rate 10 000 r/min, stabilizer mixture 0.2%, temperature 45 ℃, pressure 30 MPa, and homogenization time 120 s, and the optimum combination of ingredients was fermented okara 7% (particles sieved through 60 mesh), white sugar 6%, and milk powder 9%. The milk beverage prepared under the optimized conditions had a good particle size distribution. Its soluble solids content was 11%, stability coefficient 0.8 and centrifugal sedimentation rate 2.3%. The product was milky white, and it was a uniform system with good taste and good stability.

A method was developed for the determination of 20 phthatic acid esters in milk and dairy products by gas chromatography-mass spectrometry (GC-MS). Samples were extracted with n-hexane and separated on a DB-5MS capillary column (30 m × 0.25 mm, 0.25 μm). The injector temperature was 280 ℃,the interface temperature was 280 ℃, and the ion source temperature was 230 ℃. Under optimized conditions, the linear range was 0-10 μg/mL with a correlation coefficient greater than 0.9990. The average spike recovery rates were in the range of 80%-109%. The detection limits were respectively 1.0 and 0.5 mg/kg for DINP and DIDP and 0.05 mg/kg for 18 others. This method proved to be simple, rapid, sensitive, specific and accurate.

This study used a quadratic rotation-orthogonal composite experimental design with four independent variables at five levels each to establish optimal process conditions for industrial production of Mozzarella cheese. The process conditions investigated in this study included fermentation time, clotting time, whey pH and the amount of added NaCl. A regression model to optimize these process conditions was proposed and validated for its statistical significance. The optimal process conditions that provided the maximum yield of Mozzarella cheese (24.78%) were determined as follows: fermentation time 27.5 min, clotting time 37.5 min, whey pH 6.3, and addition of 2.07% NaCl. The resulting cheese had a nice flavor, a close, smooth and flexible texture and a homogeneous color and its fiber-drawing capacity, meltability and foaming properties were good. All these parameters were comparable to those of laboratory-made cheese and met the quality requirements for use in pizza. The optimized process parameters are suitable for large-batch production of Mozzarella cheese in industrial practice.