Table of Content

01 July 2024, Volume 47 Issue 4

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Basic Research

Effects of Different Protein Stabilization Times on Fermentation Characteristics of Ultra-high Temperature Treated Milk

WANG Lei

2024, 47(4):  1-4.  DOI: 10.7506/rykxyjs1671-5187-20240627-046

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Yogurt was fermented from milk subjected to protein stabilization at 90 ℃ for 0 (T00), 30 (T30), and 60 s (T60) followed by sterilization at 137 ℃ for 4 s and its viscosity, texture, stability and microstructure were analyzed by a rheometer, a texture analyzer, a stability analyzer and a confocal laser scanning microscope (CLSM). The results showed no significant difference in the viscosity, stability and texture between yogurts T00 and T30. The viscosity of yogurt T60 was only 55.23%–58.98% of that of T30 and T00, and the instability index was 0.19, which was significantly higher than that of T30 and T00. In summary, as the protein stabilization time became longer, the density of yogurt proteins decreased, and protein aggregation occurred.

Effect of Heat Shock-Repair Combined with Trehalose Treatment on Freeze-Drying Survival Rate of Lactiplantibacillus plantarum LIP-1

LIU Jia, WANG Ziyun, GU Tianyu, MA Zhihe, PAN Bo, SUN Chenyun, WANG Junguo

2024, 47(4):  5-11.  DOI: 10.7506/rykxyjs1671-5187-20240521-037

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In this study, the effects of heat shock-repair combined with addition of trehalose in lyoprotectant on the freeze-drying resistance and room temperature storage stability of Lactiplantibacillus plantarum LIP-1 were investigated. The results showed that the freeze-drying survival rate of the combined treatment group with heat shock-repair and 4 g/100 mL trehalose addition was 81.65%, which was significantly higher than those of the control group without heat shock-repair treatment (59.92%) and the heat shock-repair treatment group (70.23%) (P < 0.05). The damage degree of cell wall and cell membrane in the combined treatment group was significantly reduced compared with that in the control group. The addition of trehalose maintained a high proportion of unsaturated fatty acids in the cell membrane, reduced cell membrane damage, and significantly enhanced the freeze-drying resistance of the strain while improving its room temperature storage stability. After eight weeks of storage, the survival rate of the combined treatment group was 51.66%, which was significantly higher than those of the control (12.09%) and heat shock-repair (43.79%) groups (P < 0.05), and the intracellular fluorescence intensity was 1 969.23 ± 37.22, which was significantly lower than those in the control (3 475.21 ± 106.56) and heat shock-repair (2 843.95 ± 52.12) groups (P < 0.05). To sum up, the combined treatment could improve the freeze-drying resistance and room temperature storage stability of the strain.

Processing Technology

Membrane Separation Followed by Ion Exchange Chromatography for Preparation of High-Purity α-Lactalbumin

YU Miao, XU Xiaoxi, LÜ Jiaping, PANG Xiaoyang, ZHANG Shuwen, WANG Yunna

2024, 47(4):  12-18.  DOI: 10.7506/rykxyjs1671-5187-20240618-044

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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.

Analysis & Detection

Determination of 26 Inorganic Elements in Dairy Products by Inductively Coupled Plasma-Tandem Mass Spectrometry

LIU Linan, WANG Yan, WU Chunmin, WANG Fang, GAO Zhuo, CAO Meng, YANG Linlin, ZHANG Chunlin, HUANG Jianhui

2024, 47(4):  19-24.  DOI: 10.7506/rykxyjs1671-5187-20240531-039

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An inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) method was established for the analysis of 26 inorganic elements in dairy products. Under MS/MS conditions, the 26 elements were detected in the no gas, collision gas (He) or reaction gas (H2, O2, NH3/He) mode and the optimal mode was selected for each of the elements. The results showed that calibration curve with good linearity was obtained for each element in the appropriate detection mode with a correlation coefficient greater than 0.999 0. The detection limits of the 26 inorganic elements ranged from 0.000 033 61 to 0.043 71 mg/kg. The spiked recoveries were between 95.50% and 104.21%, with a relative standard deviation (RSD) ≤ 3.94% (n = 11). The contents of Na, Mg, K, Ca, P, Fe and Zn were higher and the contents of the heavy metal elements Cr, As, Cd and Pb were lower in six kinds of dairy products, all of which were lower than the national standard limits. The method was characterized by simple pretreatment, high sensitivity, low limit of detection and high accuracy and could be used for the detection of inorganic elements in dairy products.

Reviews

Research Progress on Microbial Diversity and Flavor Compounds during Kefir Fermentation

CHEN Miaomiao, ZHU Ruiyan, WEN Yuan, LI Guobin, PENG Fei

2024, 47(4):  25-30.  DOI: 10.7506/rykxyjs1671-5187-20240505-031

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Kefir is a mildly alcoholic dairy beverage made from cow’s, goat’s or sheep’s milk fermented with kefir grains, which mainly consist of lactic acid bacteria, acetic acid bacteria and yeast. Due to its unique flavor and taste, as well as outstanding probiotic effects, kefir is increasingly attracting attention from consumers. As a natural starter culture, kefir grains have a complex structure and rich microbial composition. At present, fermentation with a starter culture consisting of microbial strains isolated from kefir grains is mainly used for the industrial production of kefir. This article reviews the microbial composition of kefir grains, the impact of kefir grains from different regions and raw materials on microbial diversity during the kefir fermentation process, and summarizes the current progress in research on flavor substances in kefir.

Research Progress on Biological Functions of Milk Derived Bioactive Peptides

LOU Xiaoxiao, MA Hongpeng, GAO Jiaojiao, SHAO Wei, ZHENG Nan, ZHAO Yankun

2024, 47(4):  31-37.  DOI: 10.7506/rykxyjs1671-5187-20240627-048

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Whey protein is an important source of natural bioactive peptides with high biological value. Milk derived bioactive peptides with antioxidant, hypoglycemic, hypoglycemic and other biological activities are commonly used as raw materials for the manufacture of health products and functional foods due to the high specificity, low toxicity, diverse structures and low molecular mass and have a wide application prospect in the prevention and treatment of diseases. In this paper, the sources and structures of milk derived bioactive peptides are briefly reviewed, with emphasis on the extraction methods and biological functions of bioactive peptides, in order to provide a reference for the efficient utilization of bioactive peptides and the development of functional dairy products.

Research Progress on the Potential of Goat Milk as a Substitute for Breast Milk and Its Main Bioactive Ingredients

MEI Zhiqing, MA Haorui, LIU Yongfeng, HU Jian, SHU Qin

2024, 47(4):  38-46.  DOI: 10.7506/rykxyjs1671-5187-20240618-043

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Goat milk has a high nutritional value, is rich in protein, fat, sugar, vitamins and mineral components. It has various functional properties such as easy digestion, hypoallergenicity, intestinal improvement, cholesterol reduction and antioxidant effect, which is the closest to breast milk. In order to promote the research and development of goat milk as a potential substitute for human milk, this paper compares the composition and content of nutrients in goat milk, cow milk and breast milk, and explains the theoretical basis for and feasibility of using goat milk as a substitute for breast milk. Besides, the functional properties and separation techniques of the main bioactive substances (whey protein, casein and oligosaccharides) in goat milk are reviewed, which can provide a scientific basis for the promotion of goat milk as a replacement for breastfeeding and for its application in infant formula milk powder.

Research Progress on the Mechanism of Action of Lactiplantibacillus plantarum in Promoting the Release of Plant-Based Bioactive Substances and Its Application in Fermented Foods

LI Aoqiang, LI Zhengyu, TIAN Qiquan, ZHANG Yuxin, LI Jiaxin

2024, 47(4):  47-52.  DOI: 10.7506/rykxyjs1671-5187-20240708-051

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Lactiplantibacillus plantarum is widely used in the food fermentation, breeding and healthcare fields. It has the ability to produce high yields of acid and biological preservatives, and has beneficial effects such as immune regulation, maintaining intestinal health, and inhibiting pathogenic bacteria and tumor cell formation. Some strains of L. plantarum promote the release of plant-based bioactive ingredients and improve the biological activity and nutritional properties of plant-based foods. L. plantarum fermented foods have a unique flavor, and their nutritional components are maintained and even enhanced, which is beneficial to human health. In order to provide a reference for further research and application of L. plantarum, this article summarizes the mechanism of action of L. plantarum in promoting the release of bioactive substances, the current status of its application in fermented foods, its health effects, and new omics research approaches for L. plantarum.

Research Progress on the Anti-Infective and Metabolic Regulatory Functions of Monascus Metabolites

XU Xingmin, ZHENG Yuanrong, LIU Zhenmin, SU Miya

2024, 47(4):  53-58.  DOI: 10.7506/rykxyjs1671-5187-20240708-054

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The use of Monascus has a history of over 1 000 years in China and it is commonly used for making red yeast rice and fermented bean curd. Its metabolites demonstrate broad application potential in the fields of food, health products and medicine. This review summarizes recent advances in research on the metabolites of Monascus in terms of their antibacterial, anti-inflammatory, lipid-lowering, blood glucose-lowering, and blood pressure-lowering effects. Studies indicate that Monascus metabolites contain various functional components, such as Monascus pigments, monacolin K and γ-aminobutyric acid (GABA), which exhibit their biological activities through multiple mechanisms. Some Monascus pigments have antibacterial properties, monacolin K is an ideal lipid-lowering agent, and GABA shows a significant blood pressure-lowering effect. Additionally, Monascus metabolites demonstrate good anti-inflammatory activity and blood glucose-lowering effects, and show significant anti-inflammatory effects in inflammation models. In conclusion, Monascus metabolites have broad application prospects, but further research is needed to elucidate the mechanism of their health benefits. This review will promote their development and application in the food, health and medical fields.

Research Progress on the Hazards and Control of Bacillus subtilis in Sterilized Milk

ZHAO Jinde, ZHANG Shuli, HE Kairu, CHEN Xiaomin, LIU Yuru, ZHANG Yanliang, WU Rina, ZHANG Dexi, WU Junrui

2024, 47(4):  59-65.  DOI: 10.7506/rykxyjs1671-5187-20240531-038

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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.