Table of Content

01 September 2024, Volume 47 Issue 5

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Basic Research

Quality Evaluation of Skimmed Milk Treated with Ultra-high Pressure Jet Using Fast Gas Chromatography-Based Electronic Nose

ZHAO Pei, ZHANG Shan, WU Zijian, NIU Tianjiao, ZHAO Junyan, XUE Lu, XIAO Ran

2024, 47(5):  1-6.  DOI: 10.7506/rykxyjs1671-5187-20240708-056

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This study explored the impact of ultra-high pressure jet (UHPJ) treatment on the quality of fresh skimmed milk. After UHPJ treatment at pressures ranging from 100 to 300 MPa, the changes in the color, odor and overall flavor of skimmed milk were detected by using electronic eye, electronic nose and sensory evaluation. The results showed that the main color number of skimmed milk was white 4095, constituting 46.80%–53.83%. A total of 42 volatile flavor components such as esters, ketones, and aldehydes were detected by electronic nose. The majority of the flavor components exhibited milky, fruity, roasted, and grassy aromas. Principal component analysis (PCA) revealed that the flavor of samples treated at 300 MPa differed greatly from that of other treated samples. Sensory evaluation indicated that among the flavor attributes evaluated, milky aroma and sweetness were prominent, and there were considerable differences between different samples in terms of sweetness, peptone-like, rusty, burnt and bland flavors. Samples treated at 250 and 300 MPa generated sulfide compounds such as dimethyl sulfide that significantly enhanced the burnt and peptone-like flavors of skimmed milk. In conclusion, UHPJ treatment with 200 MPa can better retain the flavor components in skimmed milk and consequently maintain the flavor of raw milk.

Identification of Peptoniphilus asaccharolyticus Isolated from Spoiled Fermented Milk Intended for Students

GAO Jiali, WANG Xiaoru, XIAO Xiao, CHEN Jia, MENG Deshang, SUN Wei

2024, 47(5):  7-11.  DOI: 10.7506/rykxyjs1671-5187-20240708-055

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This study focuses on the identification of Peptoniphilus asaccharolyticus from spoiled fermented milk intended for students based on isolation, counting, morphological observation, biochemical identification, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and whole-genome sequencing. The results showed that the isolate grew well on PCA medium under anaerobic conditions and was identified as P. asaccharolyticus on a fully automated microbial identification system with a confidence level of 98%. By MALDI-TOF MS, it was confirmed as P. sasaccharolyticus with a comparison value of 2.241. The result of whole genome sequencing showed an average nucleotide identity (ANI) of 98.58%. The proposed method allows rapid and accurate identification of P. sasaccharolyticus and can meet the requirements of food safety detection.

Analysis & Detection

Determination of 54 Pesticide Residues in Milk by Solid-Phase Extraction Combined with Gas Chromatography-Mass Spectrometry

BAI Xiaoyun, MA Xiaochong, QI Xiaoru, SU Yuncong, ZHANG Yaoguang, LI Fei

2024, 47(5):  12-19.  DOI: 10.7506/rykxyjs1671-5187-20240627-047

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A high-throughput gas chromatography-mass spectrometry method was established for the analysis of 54 pesticide residues in milk. Samples were extracted with acetonitrile while shaking, and the extract was concentrated and purified using solid-phase extraction (SPE) on a C18 column using acetonitrile as the eluent. The external standard method was used for quantification. The results showed that good linearity was observed over the concentration range from 0 to 1.00 μg/mL, with correlation coefficient (R2) greater than 0.990. Recoveries were between 43.33% and 113.87% with a relative standard deviation (RSD) of 1.8%–19.8% (n = 6). This method is accurate, simple and suitable for large numbers of milk samples.

Detection of Common Molds and Yeasts in Low-Temperature Yogurt by TaqMan probe Real-Time Fluorescence Quantitative Polymerase Chain Reaction

ZHANG Jie, CHEN Boxu, DU Haikuan, ZHANG Zilun, YAN Taotao, CHEN Jia, ZHOU Wei

2024, 47(5):  20-24.  DOI: 10.7506/rykxyjs1671-5187-20240703-049

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In order to improve the detection efficiency of molds and yeasts in low-temperature yogurt, primers and probes were designed according to the sequences of the conserved gene elongation factor-1α (EF-1α) for molds and yeasts, respectively. A real-time fluorescence quantitative polymerase chain reaction (real-time PCR) method with TaqMan probe was established for the detection of molds and yeasts, respectively. The genomic DNA of fungi and lactic acid bacteria commonly found in low-temperature yogurt, were used as amplification templates for specificity testing. The sensitivity and repeatability were also tested, and the standard curves were constructed. The results showed that the designed primers and probes had good specificity; the sensitivity of the method was 101 and 102 CFU/mL for yeasts and molds, respectively; the coefficients of variation within and between groups in the repeatability test were less than 2%, indicating good reliability and stability; the correlation coefficients of the standard curves were higher than 0.99. Therefore, the real-time PCR method enables the rapid detection of molds and yeasts in low-temperature yogurt.

Top-down Evaluation of Uncertainties in Quantitative Assays for Microorganisms

LI Tiantian, WANG Yi, LI Zhijun, SUN Yingli, LI Caiqing, DONG Xiufang, HU Min

2024, 47(5):  25-31.  DOI: 10.7506/rykxyjs1671-5187-20240814-078

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On the basis of Microbiology of the food chain-Estimation of measurement uncertainty for quantitative determinations (ISO 19036) and Guidelines for the estimation of measurement uncertainty of food microbiological quantitative detection (RB/T 228-2023), the top-down method was used to design an experimental scheme for uncertainty evaluation in three different quantitative assays by using raw and fermented milk as samples. The uncertainty evaluation for total colony number included technical uncertainty (utech), matrix uncertainty (umatrix) and Poisson distribution uncertainty (upoisson); when the result was 9.4 × 104 CFU/mL, the extended uncertainty was 0.31 (lg (CFU/mL)). The uncertainty evaluation for maximum probable number (MPN) included utech, umatrix, and uncertainty based on the most probable number (uMPN); when the result was 24 MPN/g, the extended uncertainty was 0.94 (lg (MPN/g)). The uncertainty evaluation for total colony number that needs to confirm target microorganisms included utech, umatrix, upoisson, and confirmatory uncertainty (uconf); when the result was 22 CFU/g, the extended uncertainty was 0.29 (lg (CFU/g)).

Reviews

Research Progress on the Role of Casein Phosphopeptides in Improving the Bioavailability of Mineral Elements

QIAO Wei, XU Qian, WANG Yu, HAN Xue, LÜ Xiaohong, HOU Aiju

2024, 47(5):  32-38.  DOI: 10.7506/rykxyjs1671-5187-20240729-069

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Casein phosphopeptide, as a “mineral carrier”, can effectively improve the bioavailability of mineral elements through its special phosphoserine structure. Studies have shown that casein phosphopeptides can chelate metal cations, forming soluble complexes, which can protect mineral elements, improve the bioavailability of mineral elements in physiological environments from neutral to alkaline environments, and avoid adverse effects caused by reactions between mineral elements and simultaneously ingested food components or other mineral elements. Casein phosphopeptides can not only promote the absorption of mineral elements, but also supplement peptides with important biological activities, and therefore have broad prospects for application and development in the fields of pharmaceutical, functional food, health food and green additives.

Research Progress on the Interaction between Milk Protein and Active Molecules

XIANG Runru, MA Bohan, HU Jian, CHEN Jianghua, LIU Yongfeng

2024, 47(5):  39-44.  DOI: 10.7506/rykxyjs1671-5187-20240910-084

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As the core component of dairy products, milk proteins possess rich nutritional value and a variety of bioactive functions. There are complex interactions (covalent bonding, non-covalent bonding, etc.) between active molecules (such as polyphenols, polysaccharides and vitamins) and milk proteins. These interactions not only affect the structure and functional properties of milk proteins (such as emulsifying properties, solubility, foaming properties, and gelling properties), but also may have significant impacts on food processing and preservation, as well as the nutritional value and functionality of final products. This review summarizes the interaction mechanisms between milk proteins and several types of active molecules and their effects on functional properties. It is of great significance for a systematic understanding of the binding between milk proteins and active molecules and provides a theoretical basis for in-depth research and industrial production of dairy products.

Research Progress on the Role of Milk-Derived Exosomes in Regulating Intestinal Physiological Functions

TANG Qi, LIU Huanchen, WANG Xu, ZHANG Yan

2024, 47(5):  45-51.  DOI: 10.7506/rykxyjs1671-5187-20240729-070

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Exosomes are extracellular vesicles (EVs) with a diameter of 30–150 nm. They are widely involved in intercellular communication and disease diagnosis, and can serve as drug delivery carriers for targeted disease treatment. Due to the lack of sufficient sources and methods to obtain exosomes, their therapeutic application as drug carriers is limited. Milk contains abundant exosomes. Multiple studies have shown that milk-derived exosomes play a crucial role in preventing and treating intestinal diseases. This article reviews the extraction and identification methods of milk-derived exosomes reported in the literature. It also discusses the role of milk-derived exosomes in regulating intestinal physiological functions by protecting the intestinal barrier, alleviating intestinal inflammation, regulating the intestinal microbiota, and promoting intestinal cell proliferation. Milk-derived exosomes have various advantages such as no adverse immune reactions or inflammatory reactions. Understanding the regulatory mechanism of milk-derived exosomes on intestinal physiological functions can help further study their role in preventing and treating intestinal diseases.

Advances in Application of Organoid Models in Milk and Dairy Products

FAN Sufang, WANG Xu, ZHANG Yan

2024, 47(5):  52-57.  DOI: 10.7506/rykxyjs1671-5187-20240721-063

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Organoids are derived from adult or pluripotent stem cells through in vitro differentiation, which can recapitulate the cellular diversity, spatial organization, and physiological functions of in vivo organs or tissues. Organoid models have been widely used in drug development, precision medicine and other fields, and have begun to be applied in the field of food safety. This paper briefly introduces the development history, classification and construction of organoids and their application in the metabolomics, nutritional and functional evaluation of milk and dairy products and research on their roles in intestinal protection. It also summarizes problems existing in the construction of organoid models and discusses future prospects for their application in milk and dairy products in order to provide a reference for further application of organoid models in various fields including food safety and nutrition.

Research Progress on the Application of Selenium-Enriched Probiotics in the Dairy Industry

DONG Yingxiu, GAO Xuejun, ZHANG Minghui

2024, 47(5):  58-63.  DOI: 10.7506/rykxyjs1671-5187-20240627-045

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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.