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Recent Progress in Research on the Physicochemical Properties and Microbial Metabolism of Yogurt Fermented by Lactic Acid Bacteria LIU Huiyao, PENG Fei Journal of Dairy Science and Technology    2024, 47 (3): 49-60.   DOI: 10.7506/rykxyjs1671-5187-20240505-029 Abstract （192）   HTML （8）    PDF （1686KB）（1012）       Knowledge map    Save Lactic acid bacteria, a group of microorganisms that can ferment sugars into lactic acid, are widely used in the production of yogurt products. Different lactic acid bacteria exhibit different fermentation characteristics, which not only alter the physicochemical properties of yogurt but also have a significant impact on its nutritional value. This paper reviews the relationship between yoghurt products and microbial metabolism with a special focus on the role and influence of microorganisms in yoghurt making. The production of yogurt relies on the fermentation of specific microorganisms, such as lactic acid bacteria, which not only convert lactose to lactic acid, change the pH and texture of yogurt, but also synthesize a range of bioactive substances, such as vitamins, thereby having a positive impact on the health of consumers. This paper summarizes recent advances in understanding the fermentation mechanism of yoghurt, revealing the contribution of microbial diversity to product characteristics. In addition, this paper also discusses the health benefits of microbial metabolites in yogurt, including improving intestinal health and enhancing immunity. It is hoped that this review will provide a scientific basis and technical guidance for the research and development of yogurt products. Related Articles | Metrics

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Research Progress on Isolation, Preparation and Functional Characteristics of Postbiotics and Their Applications in Dairy Products LI Yue, REN Dayong Journal of Dairy Science and Technology    2024, 47 (3): 61-70.   DOI: 10.7506/rykxyjs1671-5187-20240415-023 Abstract （115）   HTML （3）    PDF （1742KB）（636）       Knowledge map    Save Probiotics have been extensively researched for their health advantages, but their poor stability and viability prevent them from being used in foods and medicine on a larger scale. Compared with probiotics, postbiotics have the advantages of higher safety and stability in its existing form, which avoids the limitation of probiotics. In 2021, the International Scientific Association for Probiotics and Prebiotics defined postbiotics as preparation of inanimate microorganisms and/or their components that confers a health benefit on the host including bacterial components and metabolites, such as cell-free supernatant, cell lysate, extracellular polysaccharide, peptidoglycan, short-chain fatty acids, and organic acids. Postbiotic components exhibit varying beneficial effects on the host, such as regulating immunity and lipid metabolism, anti-inflammatory, antioxidant, anti-tumor, and antibacterial activities, and on product processing as an antibacterial, stabilizing and emulsifying agent. This paper provides an overview of the methods for separating, preparing and identifying postbiotics. It also summarizes the potential functional characteristics of probiotics, their processing characteristics in dairy products and their potential application value. This review provides a theoretical basis for the application of postbiotics as good raw materials in the medical and food fields. Related Articles | Metrics

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Differences in Steroid Hormone Contents between Goat and Cow Milk at Different Lactation Stages SHARI Akang, REN Xinyang, QU Yingxin, WANG Guang, YU Mengqi, CHEN Lu, YUAN Yuxin, LI Guang Journal of Dairy Science and Technology    2024, 47 (1): 1-7.   DOI: 10.7506/rykxyjs1671-5187-20240207-007 Abstract （82）   HTML （12）    PDF （2158KB）（374）       Knowledge map    Save Purpose: To understand the differences in steroid hormone contents between goat and cow milk at different lactation stages. Methods: The contents of steroid hormones in goat and cow milk at different lactation stages were investigated using ultra-high liquid chromatography-mass spectrometry (UPLC-MS). Gradient elution was performed using 0.5 mmol/L ammonium fluoride aqueous solution as mobile phase A and methanol as mobile phase B at a flow rate of 0.3 mL/min, and the target analytes were qualitatively and quantitatively detected using an electrospray ionization (ESI) source in the multiple reactions monitoring (MRM) mode. Results: A total of 11 steroid hormones, 17α-hydroxyprogesterone, 17α-pregnenolone, epi-testosterone, pregnenolone, progesterone, androstenedione, testosterone, estradiol, estrogen, cortisol, and cortisone, were detected from goat and cow milk samples. At the early lactation stage, the contents of 17α-hydroxyprogesterone, estrogen and cortisol showed significant differences between goat and cow milk (P < 0.05), and the contents of progesterone and progesterone showed extremely significant differences (P < 0.01); at the full lactation stage, significant differences in the contents 17α-hydroxyprogesterone, 17α-pregnenolone, androstenedione, and cortisone (P < 0.05), and extremely significant differences in the contents of progesterone and pregnenolone were found (P < 0.01); at the late lactation stage, significant differences in the contents of 17α-hydroxyprogesterone, androstenedione, estrogen, and cortisol (P < 0.05) were observed as well as extremely significant differences in the content of 17α-hydroxypregnenolone, pregnenolone, and progesterone (P < 0.01). Conclusion: The differences in steroid hormone contents between goat and cow milk may be due to different pregnancy status. Related Articles | Metrics

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Research Progress on the Interaction between Milk Protein and Active Molecules XIANG Runru, MA Bohan, HU Jian, CHEN Jianghua, LIU Yongfeng Journal of Dairy Science and Technology    2024, 47 (5): 39-44.   DOI: 10.7506/rykxyjs1671-5187-20240910-084 Abstract （133）   HTML （7）    PDF （1466KB）（322）       Knowledge map    Save 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. Related Articles | Metrics

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Present Situation and Challenges of Children’s Cheese Food in China: Cheese Nutrition and Children’s Health HAO Xinyue, ZOU Junzhe, LIU Liang, REN Jing, LIN Kai, YI Huaxi, ZHANG Lanwei, GONG Pimin Journal of Dairy Science and Technology    2024, 47 (3): 41-48.   DOI: 10.7506/rykxyjs1671-5187-20240606-040 Abstract （122）   HTML （9）    PDF （2061KB）（242）       Knowledge map    Save With the development of China, children’s cheese has garnered increasing attention in the dairy industry, which has become a new growth point of China’s dairy industry. However, children’s cheeses currently available on the market are uneven, which cannot be fortified completely according to children’s nutritional needs. Their tastes are similar and their selling points are the same, which causes the public’s sensory fatigue and also go against consumers’ pursuit of clean label. Thus, the development of the children’s cheese industry is facing new challenges. In this paper, from the perspectives of children’s health and cheese nutrition, we link the needs of children of different ages for nutrition, flavor and texture with the nutrition, flavor and texture of cheese. The present situation, challenges and possible development directions of children’s cheese food in China are summarized. Related Articles | Metrics

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Progress in the Study of Microplastics Contamination in Dairy Products TANG Qi, MENG Deshang, ZHANG Yan Journal of Dairy Science and Technology    2024, 47 (1): 42-46.   DOI: 10.7506/rykxyjs1671-5187-20240326-012 Abstract （132）   HTML （9）    PDF （839KB）（214）       Knowledge map    Save Microplastics (MPs) in food have aroused widespread concern, and it has been clarified that MPs have toxic effects on cells, animals and human organoids, and that the cytotoxicity is inversely proportional to the particle size of MPs, and positively proportional to the concentration of MPs and the time of exposure; in experimental animal models, the toxic effects of MPs mainly occur in the digestive, nervous, respiratory, reproductive, and cardiovascular systems; the hazardous effects of MPs have also been identified in the human organoids of liver, intestine, heart and brain. The contamination of MPs in dairy products may occur at different stages of the production process. This paper reviews the sources, toxicological effects and detection methods of MPs contamination in dairy products, with the aim of providing a reference for the risk prevention and control of MPs in dairy products and for future research. Related Articles | Metrics

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Determination of 6S-5-Methyltetrahydrofolate Calcium in Milk Powder by Reversed-Phase High Performance Liquid Chromatography LIU Lijun, CHEN Jing, DUAN Guoxia, LI Cuizhi*, LÜ Zhiyong Journal of Dairy Science and Technology    2023, 46 (4): 35-39.   DOI: 10.7506/rykxyjs1671-5187-20230417-019 Abstract （84）   HTML （3）    PDF （2238KB）（179）       Knowledge map    Save A reversed-phase high performance liquid chromatography (RP-HPLC) method was established for the determination of 6S-5-methyltetrahydrofolate calcium in milk powder. After protein precipitation with trichloroacetic acid solution, samples were extracted with ascorbic acid solution in a hot water bath, and the extract was separated on a C18 reversed-phase column by gradient elution using a mobile phase composed of 0.1% trifluoroacetic acid solution and methanol, and the detection wavelength was set at 280 nm. Quantitative analysis was carried out by the single standard method. The results showed that the limit of quantification and detection of 6S-5-methyltetrahydrofolate calcium in milk powder samples were 150 and 50 μg/100 g, respectively. The recoveries for samples spiked at levels ranging from 150 to 600 μg/100 g were 95.0%–109.1% with relative standard deviations (RSDs) between 1.26% and 4.04%. This method is simple, accurate, with high recovery and reproducibility, and suitable for the determination of 6S-5-methyltetrahydrofolate calcium in milk powder. Related Articles | Metrics

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Research Progress on Functional Properties Changes and Application of Processed Milk β-Lactoglobulin NIU Jiaojiao, QIU Yu, LI Xin, CHEN Hongbing Journal of Dairy Science and Technology    2024, 47 (3): 71-79.   DOI: 10.7506/rykxyjs1671-5187-20240415-024 Abstract （121）   HTML （5）    PDF （2413KB）（176）       Knowledge map    Save Milk β-lactoglobulin, the major protein in whey protein, possesses a unique molecular structure that provides binding sites for many ligands, endowing it with versatile functional properties including gelation, emulsification, and foaming. Hence, it has a broad application prospect. This paper first introduces the molecular structure, ligand binding sites, gelation, emulsification, and foaming properties of β-lactoglobulin. Then, it discusses the effect of several main processing methods including heat treatment, high-pressure processing, pulsed electric field treatment, and ultraviolet radiation induction on the properties of β-lactoglobulin. Finally, it elucidates the application of β-lactoglobulin in food processing, nanomaterials and basic research, aiming to provide a theoretical and scientific reference for promoting the industrial application of β-lactoglobulin in the food industry and other related industries. Related Articles | Metrics

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Research Progress on the Role of Milk-Derived Exosomes in Regulating Intestinal Physiological Functions TANG Qi, LIU Huanchen, WANG Xu, ZHANG Yan Journal of Dairy Science and Technology    2024, 47 (5): 45-51.   DOI: 10.7506/rykxyjs1671-5187-20240729-070 Abstract （218）   HTML （6）    PDF （1561KB）（155）       Knowledge map    Save 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. Related Articles | Metrics

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Metabolomics Analysis of Fermentation Characteristics of Lactococcus lactis subsp. lactis in Soymilk HE Hai, YANG Yu, ZHOU Sisi, LIU Xiaoming Journal of Dairy Science and Technology    2024, 47 (3): 1-8.   DOI: 10.7506/rykxyjs1671-5187-20240422-026 Abstract （98）   HTML （5）    PDF （2824KB）（141）       Knowledge map    Save Most current studies on Lactococcus lactis subsp. lactis are focused on its application in bovine milk, but few studies have been conducted on its application in soymilk. The fermentation characteristics of Lactococcus lactis subsp. lactis in soymilk were analyzed by metabolomics and sensory evaluation in the present study. The results showed that Lactococcus lactis subsp. lactis strains DYNDL21-2, DYNDL1-2 and FJNDD18M8 showed good sucrose metabolism capacity, growth and acid production ability. The abundance of hexanal and various heterocyclic compounds such as furan in fermented soymilk was significantly down-regulated by DYNDL21-2 and FJNDD18M8, which effectively reduced the intensity of beany odor. Fermentation with FJNDD18M8 significantly up-regulated the abundance of acetaldehyde, acetoin and 2,3-butanedione in soymilk, enhancing the milky aroma and creamy flavor and improving the overall flavor. In conclusion, Lactococcus lactis subsp. lactis has excellent fermentation characteristics and strong metabolic capacity during soymilk fermentation, but there are some differences among strains. Related Articles | Metrics

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Analysis of Flavor Substances of Mongolian Cheese and Establishment of a Model for Evaluating Its Flavor Intensity JIA Zhibin, QIAO Xiangyu, WANG Caiyun, ZHANG Xiuxiu, LIU Lu, LI Xiaodong, HAN Renjiao Journal of Dairy Science and Technology    2024, 47 (2): 9-14.   DOI: 10.7506/rykxyjs1671-5187-20240415-020 Abstract （80）   HTML （7）    PDF （2127KB）（140）       Knowledge map    Save The volatile flavor substances of 5 representative Mongolian cheese samples collected from different regions of Inner Mongolia were determined by headspace purge and trap (PT) coupled with triple quadrupole gas chromatography (QqQ-GC), and a flavor intensity evaluation model was constructed based on principal component analysis (PCA). The results showed that a total of 86 volatile substances were identified in Mongolian cheese, among which 24 were the main volatile substances. The flavor intensity evaluation model (F = 0.353 51F1 + 0.280 46F2 + 0.198 46F3 + 0.167 56F4) showed that the cumulative contribution rate of the first four principal components was 100.000%, which included ethyl caprylate, n-hexanol, ethyl decanoate, n-decanoic acid, acetic acid, and acetaldehyde, ect. They could reflect the original data accurately. In addition, the sensory evaluation results of the 5 cheese samples were consistent with the scores from the flavor intensity evaluation model, which indicated that the constructed model could effectively evaluate the flavor of Mongolian cheese, providing a new method for the evaluation of the flavor of Mongolian cheese. Related Articles | Metrics

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Comparative Analysis of Nutrient Decay Rates of Infant Formula Milk Powder in Accelerated and Long-Term Storage Tests LI Linyao, CHU Xiaojun, HUA Jiacai, YAN Yali, GUAN Xueqing Journal of Dairy Science and Technology    2024, 47 (1): 38-41.   DOI: 10.7506/rykxyjs1671-5187-20240305-008 Abstract （68）   HTML （5）    PDF （2007KB）（138）       Knowledge map    Save According to the relevant requirements and methods specified in the Guidelines for Stability Study of Powdered Milk Formulae for Infants and Young Children (on Trial), nutrient decay in infant formula milk powder was investigated in accelerated and long-term tests. The results showed that the macronutrients and fatty acids in infant formula milk powder were relatively stable in both tests, with a decay rate of less than 5%. Vitamins did not significantly decay with a decay rate of less than 10%. The mineral iodine decayed evidently in the accelerated test, with a maximum decay rate of 11.37%. Other minerals did not significantly lose. The optional components were relatively stable in the accelerated and long-term tests, with a decay rate of less than 5%. Related Articles | Metrics

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Advances in Application of Organoid Models in Milk and Dairy Products FAN Sufang, WANG Xu, ZHANG Yan Journal of Dairy Science and Technology    2024, 47 (5): 52-57.   DOI: 10.7506/rykxyjs1671-5187-20240721-063 Abstract （131）   HTML （3）    PDF （1655KB）（135）       Knowledge map    Save 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. Related Articles | Metrics

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Determination of 21 Veterinary Drugs in Cow and Goat milk and Milk Powder by QuEChERS Combined with Ultra Performance Liquid Chromatography-Quadrupole/Orbitrap Mass Spectrometry ZHANG Shenping, QIN Yu, GU Yingjuan Journal of Dairy Science and Technology    2024, 47 (2): 24-29.   DOI: 10.7506/rykxyjs1671-5187-20240409-018 Abstract （61）   HTML （7）    PDF （2755KB）（128）       Knowledge map    Save A method for the determination of 21 veterinary drugs in cow and goat milk and milk powder was established by the QuEChERS (quick, easy, cheap, effective, rugged, safe) sample pretreatment method combined with ultra performance liquid chromatography-quadrupole/orbitrap mass spectrometry (UPLC-Q/Orbitrap MS). Chromatographic conditions, mass spectrometric parameters and pretreatment conditions were optimized. Samples were extracted with acetonitrile in the presence of anhydrous sodium sulfate, purified using a mixture of primary secondary amine (PSA) and C18, separated on an Accucore RP-MS column (100 mm × 2.1 mm, 2.7 μm), and detected by UPLC-Q/Orbitrap MS. Good linearity was observed for all the analytes in the investigated concentration ranges with correlation coefficients (r2) of greater than 0.99. The limit of quantification (LOQ) of the proposed method was 0.5 μg/kg. The average recoveries at spiked concentration levels of 0.5, 2.0 and 10.0 μg/kg were 67.2%–110.2% with relative standard deviations (RSDs) of 3.6%–17.4% (n = 6). The method is simple and sensitive, and suitable for simultaneous detection of the 21 veterinary drugs in cow and goat milk and milk powder. Related Articles | Metrics

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Impact of Interaction with Docosahexaenoic Acid on the Allergenicity of β-Lactoglobulin ZHOU Weini, WANG Jing, WU Ting, WO Yuxin, DU Yaxuan, JI Yaya, SHA Yicheng, CHEN Daichang, ZHAO Qian, LIANG Xiaona Journal of Dairy Science and Technology    2024, 47 (1): 8-13.   DOI: 10.7506/rykxyjs1671-5187-20240207-006 Abstract （146）   HTML （17）    PDF （3336KB）（125）       Knowledge map    Save β-lactoglobulin (β-LG) is a major allergen in cow’s milk. In this study, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, circular dichroism (CD) spectroscopy, molecular docking, and indirect competitive enzyme-linked immunosorbent assay were used to explore the interaction of docosahexaenoic acid (DHA) with β-LG and its influence on the allergenicity of β-LG. The results showed that the binding of DHA to β-LG significantly changed the microenvironment of the aromatic residues of β-LG and increased its polarity. DHA bound to β-LG to form a stable complex through hydrophobic interactions, changing the secondary structure of β-LG and resulting in folding of its backbone. The relative content of β-sheet increased and then decreased with increasing concentration of DHA, while the relative content of α-helix showed an opposite trend. However, the relative contents of β-turn and random coil showed irregular changes. In addition, the antigenicity of β-LG decreased after combination with DHA, and the immunoglobulin E (IgE) binding ability inhibition rate was about 29% by 3 mmol/L DHA. Related Articles | Metrics

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Effects of Heat Treatment Conditions on Physicochemical Properties and Functionality of Camel Whey Protein CHEN Qi, ZHANG Xiurong, HE Jing, JI Rimutu Journal of Dairy Science and Technology    2023, 46 (4): 1-9.   DOI: 10.7506/rykxyjs1671-5187-20230213-010 Abstract （2）   HTML （12）    PDF （3090KB）（124）       Knowledge map    Save Whey protein is an important component of milk, but heat treatment during sterilization has a certain impact on the structure and properties of whey protein. Therefore, this study investigated the effect of different heat treatments on the denaturation degree, physicochemical properties and functionality of camel whey protein, which was separated from camel milk heat-treated under different conditions, 65 ℃/30 min, 85 ℃/15 s, 125 ℃/4 s and 135 ℃/4 s, after milk fat and casein precipitation. The results showed that whey protein treated at 65 ℃ for 30 min had the highest turbidity (0.14), particle size (0.24 μm), zeta potential (?9.54 mV), solubility (24.57 mg/mL), and relative content of α-helix (31%) as well as the lowest relative contents of β-turn (13%) and random coil (19%); the water-holding capacity (WHC), foaming capacity and emulsifying capacity were significantly increased by the heat treatment, which indicated that 65 ℃/30 min treatment resulted in the smallest denaturation degree of whey protein and improvements in its functional properties such as emulsifying capacity, foaming capacity, WHC and oil-holding capacity (OHC) without significantly changing its physicochemical properties. With an increase in the heating temperature, the particle size of whey protein under 85 ℃/15 s treatment was increased to 0.32 μm, and the solubility was reduced to 22.34 mg/mL, but its functionality was improved compared with that of raw milk whey protein. Treatment at 125 ℃ for 4 s or 135 ℃for 4 s led to a large number of whey protein denaturation, destroyed the secondary structure, increased the particle size and turbidity, decreased the solubility, and worsened the functional properties. Related Articles | Metrics

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Analysis of Volatile Compounds in Three Milks with Different Fat Contents by GC × GC-TOFMS WANG Haitao, SHEN Xiao, YAO Lingyun, SUN Min, WANG Huatian, FENG Tao Journal of Dairy Science and Technology    2024, 47 (1): 26-32.   DOI: 10.7506/rykxyjs1671-5187-20240415-021 Abstract （73）   HTML （5）    PDF （2909KB）（123）       Knowledge map    Save In this study, headspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (HS-SPME-GC × GC-TOFMS) was used to analyze the volatile compounds in whole (WM), low-fat milk (LFM) and non-fat milk (NFM). Altogether 49 volatile compounds were detected, among which methyl ketones with odd-numbered carbon chain lengths such as 2-nonanone and 2-undecanone constituted the main flavor compounds of WM. Using partial least squares discriminant analysis (PLS-DA), a model which could well differentiate among the 3 milks was developed and it was found to have good variance and cross-validation predictive ability. Nine differential key aroma compounds were identified using variable importance in the projection (VIP) > 1, P ≤ 0.05 and their contents ≥ 1% as criteria, which may be the main factors contributing to the differences in flavor profiles among the 3 milks. The heatmap from clustering analysis indicated that NFM had poor sensory performance due to the presence of off-flavor compounds (e.g., hexadecanal), whereas WM and LFM contained more aroma compounds, having a full and rich sensory aroma profile. The HS-SPME-GC × GC-TOFMS method can provide theoretical guidance for dairy flavor improvement and dairy flavoring formulation. Related Articles | Metrics

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Advances in Techniques for Protease Detection in Milk and Milk Products LIANG Jianying, TANG Shuo, LIU Lijun, HUANG Xiaoyan, YUE Hong, HU Wenhui, LI Cuizhi Journal of Dairy Science and Technology    2024, 47 (3): 80-85.   DOI: 10.7506/rykxyjs1671-5187-20240326-010 Abstract （190）   HTML （7）    PDF （1769KB）（119）       Knowledge map    Save The proteases in cow’s milk have a great influence on the flavor and quality, especially on the shelf life of dairy products, but there is no uniform reference standard for the detection of protease activity in dairy products. This paper elaborates the sources, types and characteristics of protease in cow’s milk, and summarizes recent progress in the detection of the activity of different types of protease in cow’s milk, pointing out that the precise detection of protease activity in milk has great significance for dairy production and quality assurance. Related Articles | Metrics

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Effect of Secondary Homogenization on the Quality of Ultra-High Temperature Sterilized Whipped Cream WANG Jidong, ZHENG Yuanrong, LIU Zhenmin Journal of Dairy Science and Technology    2023, 46 (5): 16-21.   DOI: 10.7506/rykxyjs1671-5187-20231110-054 Abstract （78）   HTML （2）    PDF （2886KB）（112）       Knowledge map    Save In this research, the effect of different secondary homogenization pressures on the quality of ultra-high temperature instantaneous sterilized (UHT) whipped cream was analyzed. The results showed that secondary homogenization of whipped cream at pressures ranging from 4 to 8 MPa shifted the size distribution of the emulsion droplets toward smaller values, and increased the apparent viscosity, which improved the stability of the emulsion. However, too high homogenization pressure led to fat aggregation within the emulsion droplets, affecting the apparent viscosity and foam stability of whipped cream. With an increase in secondary homogenization pressure, whipping time of whipped cream was prolonged, whipping rate, foam stability and hardness was decreased, and even at 12 MPa, it could not be whipped into shape. Therefore, it is recommended that the secondary homogenizing pressure be controlled in the range of 4 to 6 MPa. Related Articles | Metrics

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Research Progress on the Application of Selenium-Enriched Probiotics in the Dairy Industry DONG Yingxiu, GAO Xuejun, ZHANG Minghui Journal of Dairy Science and Technology    2024, 47 (5): 58-63.   DOI: 10.7506/rykxyjs1671-5187-20240627-045 Abstract （116）   HTML （4）    PDF （1669KB）（111）       Knowledge map    Save 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. Related Articles | Metrics

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Determination of Nitrite and Nitrate in Milk Products by Ion Chromatography YIN Jie, ZHENG Guojian, YE Yinying Journal of Dairy Science and Technology    2024, 47 (1): 14-18.   DOI: 10.7506/rykxyjs1671-5187-20240401-014 Abstract （90）   HTML （6）    PDF （2023KB）（110）       Knowledge map    Save An ion chromatography with conductivity detector (IC-CD) method was developed for the determination of nitrite and nitrate in milk products. Samples were dissolved in water and added with potassium ferrocyanide and zinc sulphate solutions for protein precipitation. The supernatant was cleaned up on C18, Ag, and Na solid-phase extraction (SPE) columns, and analyzed by IC-CD. An external standard method was used for quantification. The IC-CD method was validated. Good linearity between the concentrations of nitrite (NaNO2) and nitrate (NaNO3) in the range of 0.01–0.20 mg/L and 0.1–2.0 mg/L, respectively and peak area was observed with correlation coefficient equal to or higher than 0.99. The limits of quantitation for nitrite and nitrate were 0.2 and 0.4 mg/kg, respectively. The spiked recoveries ranged from 92.5% to 102.0%, and the relative standard deviation (RSD) for precision from 1.5% to 6.6%. This method is accurate, repeatable, simple and applicable to the determination of nitrite and nitrate in milk products. Related Articles | Metrics

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Contamination Status and Sources of Chlorate and Perchlorate in Infant Formula Milk Powder LI Linyao, GAO Chao, CHU Xiaojun, LIU Xiaoping, HUA Jiacai, ZHENG Huayan Journal of Dairy Science and Technology    2023, 46 (4): 28-34.   DOI: 10.7506/rykxyjs1671-5187-20230602-030 Abstract （76）   HTML （3）    PDF （1954KB）（109）       Knowledge map    Save Our aim was to understand the pollution levels and sources of chlorate and perchlorate in infant formula milk powder and to evaluate the risk of dietary exposure to chlorate and perchlorate in infants and young children. A total of 165 batches of samples were collected from the water, cow milk, and ingredients used, as well as 131 batches of infant formula milk powder. Chlorate and perchlorate in each sample were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the data obtained were statistically analyzed. The results showed that chlorate and perchlorate were undetectable in the water samples. Cow milk was more severely polluted by perchlorate than by chlorate. Some ingredients were also found to contain chlorate and perchlorate. Infant formula milk powder was contaminated with chlorate and perchlorate, with average contents of 34.3 and 14.5 μg/kg, respectively. The average dietary exposure levels to chlorate and perchlorate for infants aged 0–6 months were 0.71 and 0.28 μg/(kg·d), respectively, which were at an acceptable level. Infant formula milk powder and the raw materials used were found to be contaminated by chlorate and perchlorate. Related Articles | Metrics

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Determination of 25 β-Receptor Agonist Residues in Milk and Dairy Products by PRiME MCX Solid Phase Extraction Column Combined with Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry FAN Lixin, YANG Liqiong, REN Xiaowei, YANG Cengceng, MENG Zhijuan, FAN Sufang Journal of Dairy Science and Technology    2024, 47 (3): 16-25.   DOI: 10.7506/rykxyjs1671-5187-20240606-041 Abstract （88）   HTML （3）    PDF （3673KB）（102）       Knowledge map    Save A method for the determination of 25 β-receptor agonist residues in milk and dairy products was established based on ultra-high performance liquid chromatography-tandem mass spectrometry. Samples were enzymatically hydrolyzed in 0.2 mol/L ammonium acetate solution at pH 5.2 for 16 h. After the removal of fat and protein through glass fiber filter paper, the filtrate was purified by solid phase extraction (SPE) using a PRiME MCX solid phase extraction column, and separated on a Waters BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.1% formic acid in water. Mass spectrometry was performed using an electrospray ionization source (ESI) in the positive ion mode with multiple reaction monitoring (MRM), and quantitative determination was performed using the internal standard method. The proposed method showed good linearity for all analytes in the concentration range of 0.2–50.0 ng/mL with coefficients of determination (R2) greater than 0.996; the recoveries ranged from 80.3% to 106.2% with relative standard deviations (RSDs) of 0.6%–8.5% (n = 6). The limits of detection (LOD) were 0.05–0.10 μg/kg, and the limits of quantification (LOQ) were 0.10–0.20 μg/kg. This method is simple, efficient and suitable for the determination of the 25 β-receptor agonist residues in milk and dairy products. Related Articles | Metrics

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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 Journal of Dairy Science and Technology    2024, 47 (5): 12-19.   DOI: 10.7506/rykxyjs1671-5187-20240627-047 Abstract （84）   HTML （3）    PDF （1802KB）（93）       Knowledge map    Save 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. Related Articles | Metrics

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Optimization of a Method for the Detection of 1,2-Propanediol in Infant Formula LIU Yuxuan, MENG Genhua, LIN Tingjuan, GUO Ruifang Journal of Dairy Science and Technology    2024, 47 (2): 49-55.   DOI: 10.7506/rykxyjs1671-5187-20240116-002 Abstract （61）   HTML （4）    PDF （3005KB）（90）       Knowledge map    Save According to the first method for the determination of 1,2-propanediol in foods specified by the national food safety standard GB 5009.251-2016, 1,2-propanediol was extracted from milk powder using acetonitrile and was detected using a gas chromatograph (GC). Extraction solvent and standing time were investigated by one-factor-at-a-time method. Furthermore, response surface methodology (RSM) was employed to optimize oscillation time and standing time based on 1,2-propanediol recovery. The optimum extraction conditions were determined as acetonitrile, 4 ℃, 94–102 s and 1.2–1.4 h for extraction solvent, standing temperature, oscillation time and standing time, respectively. Under these conditions, the spiked recovery range of 1,2-propanediol was 95.2%–99.8%. The coefficient of variation for repeatability of the method was 1.62%, and it had good selectivity. The optimized method is suitable for the determination of 1,2-propanediol in milk powder. Related Articles | Metrics

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Analysis of Reasons for Protein Coagulation in Ultra-High Temperature Milk at the End of Shelf-life WANG Chuanbao, HE Xiong, LI Jiaxin, LIN Lin Journal of Dairy Science and Technology    2023, 46 (4): 16-21.   DOI: 10.7506/rykxyjs1671-5187-20230630-033 Abstract （1）   HTML （4）    PDF （2448KB）（90）       Knowledge map    Save The protein content, pH, color, colonies number, average particle size, zeta potential, degree of proteolysis and proteinase activity of ultra-high temperature (UHT) milk with and without protein coagulation and commercial pure milk samples were determined to analyze the reasons for protein coagulation in UHT milk at the end of self-life. The results showed that the total protein content of coagulated milk samples was 2.9 g/100 g, which was not significantly different from that of milk samples without protein coagulation, but the pH decreased slightly. The total color difference (ΔE) and brightness value (L*) decreased to 68.05 and 67.56, respectively, indicating that the color became dark, and the total bacterial count increased to 1.92 (lg(CFU/mL)). The proteinase activity was 2 565.33 U/L, the degree of proteolysis was 17.07%, the average particle size was 685.8 nm, and the zeta potential increased to ?19.97 mV; these data were all significantly higher than those of milk samples without protein coagulation and commercial pure milk. The trend of changes in proteinase activity was basically consistent with that of the degree of proteolysis, particle size and zeta potential for all samples tested. Protein coagulation in UHT milk at the end of shelf life may be attributed to protein hydrolysis due to increased protease activity and physical deposition caused by the enlargement of casein micelles during long-term storage at ambient temperature. Related Articles | Metrics

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Analysis of Amino Acid Composition in Infant Formula LI Linyao, CHU Xiaojun, HUA Jiacai, SU Xiaofang, KANG Qiaojuan, GAO Chao Journal of Dairy Science and Technology    0, (): 1-6.   Abstract （50）            Knowledge map    Save The composition and content of amino acids in infant formula sold in China were investigated in comparison with human milk at different lactation stages. An amino acid analyzer was used to detect the contents of free and hydrolyzed amino acids in commercial infant formula, and total amino acid content and the proportion of individual amino acids were calculated. The results showed that free amino acids were detected in some of the 12 samples, while hydrolyzed amino acids were detected in all these samples. The average concentration of most amino acids was close to that of human milk at 1 to 60 d of lactation, and higher than that of human milk at 61 to 180 d. The average ratio of essential to total amino acids was 46.43%, which was close to that of human milk. The proportions of methionine and tryptophan to total amino acids were higher than those of human milk, the proportions of arginine and cystine to total amino acids were lower than those of human milk, and the proportion of other amino acids to total amino acids was close to that of human milk. This study reveals the difference in amino acid content between commercial infant formula and human milk. Related Articles | Metrics

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Electronic Nose Based on Gas Chromatography for Analysis of Flavor Changes of Milk with Different Fat Contents during Storage ZHANG Shan, LI Wen, ZHANG Yuting, WEI Xuetong, SUN Ying, XUE Lu, ZHAO Pei, NIU Tianjiao Journal of Dairy Science and Technology    2024, 47 (3): 26-34.   DOI: 10.7506/rykxyjs1671-5187-20240422-028 Abstract （65）   HTML （2）    PDF （2621KB）（84）       Knowledge map    Save During storage, milk is prone to different degrees of oxidative degradation of fat with varying storage conditions, which changes the aroma components of milk. In this study, electronic nose based on gas chromatography (GC) and sensory evaluation were used to compare the changes in the composition of volatile flavor compounds and sensory properties of pasteurized whole milk, low-fat milk and skim milk (fat contents of 4, 1.4 and 0 g/100 mL) during storage at different temperatures. The results showed that all three milks maintained good flavor characteristics during storage at 4 ℃. The composition of flavor substances in whole milk was more complex, where 43 volatile compounds were identified, and no obvious stale flavor was perceived. The decreasing order of difficulty of fat oxidation was whole milk > low-fat milk > skim milk. Nonanal, a marker of lipid oxidation, was detected in both skim milk and low-fat milk. Methyl ketones derived from lipid oxidization such as 2-butanone, 2,3-butanedione, 2-hexanone, 2-heptanone and 2-undecanone were detected in skim milk during storage. The results of sensory evaluation were basically consistent with those of electronic nose. The sweetness and milky flavor of whole milk were more prominent, the flavor of low-fat milk was relatively bland, and skim milk tasted slightly bitter after 21 days of storage at 25 ℃. The findings of this study will provide a scientific basis for monitoring the flavor changes of milk products during storage and improving the quality of milk products. Related Articles | Metrics

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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 Journal of Dairy Science and Technology    2024, 47 (5): 20-24.   DOI: 10.7506/rykxyjs1671-5187-20240703-049 Abstract （70）   HTML （3）    PDF （2127KB）（80）       Knowledge map    Save 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. Related Articles | Metrics

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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 Journal of Dairy Science and Technology    2024, 47 (5): 32-38.   DOI: 10.7506/rykxyjs1671-5187-20240729-069 Abstract （86）   HTML （3）    PDF （2238KB）（78）       Knowledge map    Save 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. Related Articles | Metrics

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Top-down Evaluation of Uncertainties in Quantitative Assays for Microorganisms LI Tiantian, WANG Yi, LI Zhijun, SUN Yingli, LI Caiqing, DONG Xiufang, HU Min Journal of Dairy Science and Technology    2024, 47 (5): 25-31.   DOI: 10.7506/rykxyjs1671-5187-20240814-078 Abstract （114）   HTML （2）    PDF （2351KB）（77）       Knowledge map    Save 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)). Related Articles | Metrics

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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 Journal of Dairy Science and Technology    2024, 47 (5): 1-6.   DOI: 10.7506/rykxyjs1671-5187-20240708-056 Abstract （108）   HTML （18）    PDF （1819KB）（73）       Knowledge map    Save 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. Related Articles | Metrics

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Evaluation of the Measurement Systems for Chromium Determination in Milk Powder by ICP-MS and GF-AAS FENG Hao, SU Ying, GENG Yawen, GUO Qingqing, LIN Jin, ZHOU Taohong Journal of Dairy Science and Technology    2024, 47 (1): 19-25.   DOI: 10.7506/rykxyjs1671-5187-20240409-017 Abstract （78）   HTML （4）    PDF （3240KB）（73）       Knowledge map    Save Chromium is an important analytical item in food quality and safety monitoring. Two common methods to detect chromium in food: graphite furnace atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS) are specified in the National Food Safety Standard Determination of Chromium in Foods (GB 5009.123-2023). This study systematically evaluated the stability, bias, linearity, repeatability, and reproducibility of the two methods using Minitab statistical tools by control chart, independent sample, t test and analysis of variance (ANOVA) methods. The results showed that no outliers were found in the range or mean plots for each method, with within-group errors under statistical control and good stability; the results of gauge linearity and bias analysis showed no significant bias or significant linear error; the gauge repeatability and reproducibility (R&R) analysis showed good repeatability and reproducibility. Two-way ANOVA showed that the sample was the only factor that significantly affected the measurement error. Research variation analysis showed that the measurement system error was acceptable. ICP-MS and GF-AAS can effectively ensure the reliability and repeatability of the detected data of chromium content in milk powder. The findings of this study can not only provide a scientific basis for laboratory analysis and control of measurement system errors, but also provide a reference for the evaluation of measurement systems for the determination of other heavy metals in dairy products and other foods. Related Articles | Metrics

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Identification of Peptoniphilus asaccharolyticus Isolated from Spoiled Fermented Milk Intended for Students GAO Jiali, WANG Xiaoru, XIAO Xiao, CHEN Jia, MENG Deshang, SUN Wei Journal of Dairy Science and Technology    2024, 47 (5): 7-11.   DOI: 10.7506/rykxyjs1671-5187-20240708-055 Abstract （77）   HTML （8）    PDF （2355KB）（71）       Knowledge map    Save 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. Related Articles | Metrics

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Correlation between Physicochemical Indexes and Acidity of Sheep Milk in Different Lactation Periods SHEN Yufei, ZHANG Yan, TONG Fenfen, WANG Shuangshuang, HU Qisheng, XU Liqing, SONG Yuxuan, GE Wupeng Journal of Dairy Science and Technology    2024, 47 (6): 8-14.   DOI: 10.7506/rykxyjs1671-5187-20240708-057 Abstract （93）   HTML （16）    PDF （2183KB）（71）       Knowledge map    Save This study explored changes in the acidity of sheep milk across different lactation periods and the key factors affecting the acidity of sheep milk. The pH, titratable acidity, fat content, protein content and composition, total sugar content, mineral content, density, lactose content, fatty acid composition and content were analyzed, and the correlation between physicochemical indexes and acidity was investigated. The results indicated that the acidity of raw sheep milk was closely related to lactation stages. The highest acidity was observed in the early lactation period, which then gradually decreased as lactation progressed. Acidity changes were primarily associated with the protein content, fat content, fatty acid composition, total sugar content, lactose content, mineral content, and density of the milk. Among these, the protein content showed the strongest correlation with acidity changes, whereas fatty acid content had a relatively low correlation with acidity variations. Related Articles | Metrics

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Uncertainty Evaluation for the Determination of Nicotinamide in Milk Powder by Ultra-High Performance Liquid Chromatography CUI Suxia Journal of Dairy Science and Technology    2024, 47 (1): 33-37.   DOI: 10.7506/rykxyjs1671-5187-20240401-013 Abstract （73）   HTML （1）    PDF （4369KB）（69）       Knowledge map    Save The uncertainty in the determination of nicotinamide in milk powder by ultra-high performance liquid chromatography was evaluated. According to the technical normal “Evaluation and Expression of Uncertainty in Measurement” (JJF 1059.1-2012), a mathematical model was established, and the source of each uncertainty component in the mathematical model was analyzed and calculated. The results showed that the uncertainty in nicotinamide determination mainly came from the dilution of the standard solution. In addition, the average content of nicotinamide in milk powder was 5 007 μg/100 g with an expanded uncertainty of about 197 μg/100 g (k = 2). Related Articles | Metrics

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Development of Quantitative Loop-Mediated Isothermal Amplification for Rapid Detection of Streptococcus thermophilus and Lactobacillus bulgaricus in Fermented Milk ZHOU Shuaikang, HU Lianxia, WANG Mengyang, LI Miao, LU Han, WANG Shijie Journal of Dairy Science and Technology    2024, 47 (3): 9-15.   DOI: 10.7506/rykxyjs1671-5187-20240505-033 Abstract （124）   HTML （8）    PDF （2254KB）（69）       Knowledge map    Save In this study, a rapid and quantitative method for the detection of viable bacterial counts of Streptococcus thermophilus and Lactobacillus bulgaricus in fermented milk was established using propidium monoazide (PMA) combined with quantitative loop-mediated isothermal amplification (PMA-qLAMP). The PMA treatment conditions for S. thermophilus and L. bulgaricus were optimized. A linear relationship was fitted between the logarithm of bacterial concentration and cycle threshold (Ct) value. The limit of quantification for S. thermophilus and L. bulgaricus was 7.2 × 103 and 5.6 × 104 CFU/g, respectively. The PMA-qLAMP method was applied to measure viable bacterial counts in commercial fermented milk, demonstrating good sensitivity and practicality. Related Articles | Metrics

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Research Progress on the Functionality of Probiotic Fermented Dairy Products ZHANG Yuxin, LI Zhengyu, RAO Fulin, TIAN Qiquan, LI Aoqiang, LI Jiaxin Journal of Dairy Science and Technology    2024, 47 (2): 56-60.   DOI: 10.7506/rykxyjs1671-5187-20240422-027 Abstract （148）   HTML （7）    PDF （1749KB）（67）       Knowledge map    Save Probiotic fermented dairy products are rich in beneficial microorganisms such as lactic acid bacteria as well as a variety of bioactive substances, conferring multiple health benefits to consumers. This paper reviews the latest research developments in probiotic fermented dairy products, including the types and functions of probiotics and their roles in treating inflammatory bowel disease, improving obesity, enhancing cognitive function, alleviating allergic symptoms, maintaining bone health, combating constipation, lowering cholesterol, and managing diabetes. The paper concludes with a summary and outlook on the future development directions of probiotic fermented dairy products, highlighting the importance of the development, clinical testing and market exploitation of personalized products. It is hoped that this review will lay a theoretical foundation for further research into probiotic fermented dairy products. Related Articles | Metrics

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Determination of Vitamin C in Formulas for Special Medical Purpose Intended for Infants by Liquid Chromatography WU Xiuping, CHENG Baiyu, XU Xiaoqian, JIANG Ruiyu Journal of Dairy Science and Technology    2024, 47 (3): 35-40.   DOI: 10.7506/rykxyjs1671-5187-20240521-036 Abstract （66）   HTML （3）    PDF （2232KB）（62）       Knowledge map    Save A liquid chromatography (LC) method for the determination of vitamin C in formulas for special medical purpose intended for infants was established and validated. The sample was reduced, purified using an HLB solid phase extraction (SPE) cartridge, filtered through a 0.45 μm filter, and analyzed by hydrophilic interaction liquid chromatography (HILIC). The calibration curve was found to be linear in the concentration range of 0–50 μg/mL with correlation coefficient over 0.999. The limit of quantitation (LOQ) was 3.0 mg/100 g. Recoveries of spiked samples ranged from 95.2% to 102.8% with relative standard deviation (RSD) between 1.22% and 3.62%. The method is characterized by simple operation, accurate results and good reproducibility and suitable to determine vitamin C in formulas for special medical purpose intended for infants. Related Articles | Metrics

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Screening, Identification and Culture Condition Optimization of Lactiplantibacillus plantarum RT-6 Producing a High Amount of Exopolysaccharide HUANG Xiaoyu, HAN Jin, YU Wenhui, WU Zhengjun Journal of Dairy Science and Technology    2024, 47 (2): 15-23.   DOI: 10.7506/rykxyjs1671-5187-20240409-019 Abstract （95）   HTML （1）    PDF （3445KB）（57）       Knowledge map    Save Exopolysaccharides (EPS) from Lactiplantibacillus plantarum have been found to possess a variety of biological activities such as antitumor and antioxidant, but few studies on the synthesis of EPS by L. plantarum in skim milk have been reported. The aim of the present study was to screen L. plantarum with high EPS production capability in skim milk, which will be great significance to the application of L. plantarum in dairy products. L. plantarum RT-6 (CGMCC No. 26778), with a high capability of producing EPS, was isolated from homemade yogurt collected in Guilin, Guangxi, China by the colony thread-drawing method. Its EPS producing capability was compared with that of other L. plantarum strains. The culture conditions for EPS production by L. plantarum RT-6 were optimized using one-factor-at-a-time (OFAT) method and response surface methodology (RSM). It was found that among all tested L. plantarum strains, RT-6 exhibited the highest EPS yield when cultured in reconstituted skim milk, whereas most other strains grew slowly or even could not grow. The optimal culture conditions were determined as 39 h, 32 ℃, 101 mg/mL and 1.488 mmol/L for fermentation time, fermentation temperature, skim milk concentration and concentration of mixed essential amino acids, respectively. Under the optimized conditions, the yield of EPS was 241.1 mg/L, 2.6 times higher than that before optimization. Related Articles | Metrics