To investigate the correlation between the beany odor of raw cow’s milk and feed types, this study selected two samples of raw cow’s milk with beany odor and five common feeds: soybean meal, alfalfa, flaked corn, oat grass, and corn silage, and measured their volatile flavor compounds by headspace solid phase microextraction-gas chromatography-mass spectrometry (GC-MS). Key flavor compounds were identified using relative odor activity value (ROAV). The results indicated that acids and aldehydes contributed primarily to the beany odor of raw milk. A total of 49 volatile substances were identified in the two milk samples, among which hexanoic acid, octanoic acid, decanoic acid, decanal, nonanal, (E)-2-octenal, and (E)-2-decenal were the main beany odor substances. A total of 257 volatile substances were detected in all feed samples, including decanal, nonanal, and (E)-2-octenal. According to ROAV analysis, the beany odor compounds were more abundant in the feed samples than in the milk samples. The relative contents of beany odor compounds in the feed samples followed the following decreasing order of alfalfa > oat grass > soybean meal > flaked corn > corn silage, and flaked corn exclusively contained vanillin, with a strong milky aroma.

According to the opinions of the state administration for market supervision on standardizing the use of rapid food detection, the performance of commercial colloidal gold immunochromatographic test strips for rapid in situ identification of bovine-, ovine- and caprine-derived ingredients in dairy products were evaluated in terms of application scope, detection limit, cross-reaction rate, sensitivity, false negative rate, false positive rate and coincidence rate with the results of the reference method. The results showed that the application scope of the test strip for bovine-derived ingredients was raw milk, and the detection limit was 5% (V/V); the application scope of the test strip for ovine- and caprine-derived ingredients was raw ovine and caprine milk, and the detection limit was 0.3% (V/V). Both test strips had no cross-reaction with enrofloxacin, sulfamethazine, dexamethasone, tetracycline or aflatoxin M1. The sensitivity, false positive rate and false negative rate of the test strips were 100%, 0% and 0%, respectively. The coincidence rate with the results of the reference method was high. In conclusion, the colloidal gold immunochromatographic test strips have high accuracy, and can be used for rapid in situ screening of adulterated milk.

Pasteurization and ultra-high temperature treatment can kill most microorganisms in milk. However, since some bacteria such as Bacillus subtilis can resist pasteurization and ultra-high temperature treatments, even the most stringent heat treatments used to eliminate pathogenic microorganisms in the dairy industry cannot completely inactivate all microorganisms. In addition, highly heat-resistant spores can survive ultra-high temperature processing, so sterilized milk may be contaminated, causing bacterial spoilage in milk and dairy products during storage. In this review, the harms of Bacillus subtilis and its spores, spoilage-causing enzymes and biofilm to sterilized milk and the control measures for them are summarized so as to provide strategies for the prevention and control of Bacillus subtilis in sterilized milk and the quality assurance of milk and dairy products.

In this study, ion exchange chromatography was employed to prepare high-purity α-lactalbumin from whey protein powder obtained from raw cow’s milk by sequential membrane separation and spray drying. The results showed that α-lactalbumin constituted 21.04% of the true protein in the permeate obtained using a 50-nm pore-sized ceramic membrane with three-fold concentration, one cycle of microfiltration and two cycles of washing, which was higher than that obtained using a 100-nm pore-sized ceramic membrane (15.84%). The permeate was spray dried and separated by ion exchange chromatography. Good chromatographic separation of α-lactalbumin and β-lactoglobulin was achieved with increasing NaCl concentration from 0 to 0.5 mol/L at up to 10 column volumes, and 98.18% pure α-lactalbumin and 97.82% pure β-lactoglobulin were obtained. The results of this study provide support for the industrial preparation of high-purity α-lactalbumin.

The separation of ingredients from raw milk is an essential step during the production of dairy products. Membrane separation technology has been applied in the dairy processing industry for decades and has increasingly become indispensable in solving some problems such as separation, concentration, sterilization and in developing new dairy products. In this paper, the main applications of membrane separation technology in the dairy industry, including milk standardization, protein separation, whey desalination and waste water utilization are reviewed, in order to provide reference for process selection and optimization.

A method for determining urea in milk and milk powder was developed using high performance liquid chromatography with fluorescence detection (HPLC-FLD). Samples were extracted with a mixture of water and ethanol, the supernatant was derivatized with a solution of xanthydrol in acidic condition. The chromatographic separation was performed on a reversed-phase C18 column using a mobile phase consisting of acetonitrile and sodium acetate solution. The derivatized products were separated and tested using a fluorescence detector at λex 213 nm and λem 308 nm. The method showed a good linear relationship in the range of 0.1–10.0 μg/mL, with R2 > 0.999. The spiked recoveries of urea in formula milk powder and liquid milk samples were in the range of 104%–106% and 83.4%–101% with RSD 2.1% –5.7% and 3.2%–4.9%, respectively. The limits of detection (LODs) in formula milk powder and liquid milk were 30 and 12 mg/kg, respectively. This method proved rapid, sensitive, reliable and reproducible.