Table of Content

01 March 2019, Volume 42 Issue 2

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Basic Research

Amino Acid Analysis and Nutritional Evaluation of Mare Milk and Traditional Fermented Mare Milk in Xinjiang and Inner Mongolia

GUO Linyi, SUN Huiyang, MA Jie, WANG Haiyan, WU Xiaoyong, ZHU Linsheng, GENG Wei, GE Wupeng

2019, 42(2):  1-6.  DOI: 10.15922/j.cnki.jdst.2019.02.001

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The aim of this paper is to explore the amino acid composition and nutritional evaluation of mare milk and traditional fermented mare milk in two pasture areas of western China. In this study, 40 samples of mare milk and traditional fermented mare milk were collected in the main pastoral areas of Xinjiang and Inner Mongolia. An amino acid automatic analyzer and high performance liquid chromatography were used to determine the composition and content of free amino acids and hydrolyzed amino acids in the samples. The obtained data were analyzed using analysis of variance (ANOVA) and nutritional evaluation was performed. The results showed that there was no significant difference in the total amino acid of mare milk in both areas (P > 0.05); the free amino acid contents of two fermented mare milk samples were generally significantly increased relative to their unfermented counterparts (P < 0.05), and new amino acids with special physiological activities were produced such as gamma-aminobutyric acid (GABA), beta-aminoisobutyric acid (BAIBA) and gammahydroxylysine; the content of sweet amino acid Xinjiang mare milk was significantly increased after fermentation, and the total amino acid content was higher than in fresh mare milk, indicating that fermentation helped improve the flavor of mare milk; the essential amino acid index values of fresh and fermented mare milk from the two areas were all greater than 95, indicating that both fresh and fermented mare milk were high-quality protein sources. Moreover, the nutritional evaluation of fermented mare milk was higher than fresh mare milk in each area.

Analysis of Factors Affecting Somatic Cell Counts and Milk Composition of Chinese Holstein Cows in Ningxia

ZHANG Haiping, WANG Haiyan, GAO Peng, ZHANG Jing, LIANG Xiuzhen, GE Wupeng

2019, 42(2):  7-12.  DOI: 10.15922/j.cnki.jdst.2019.02.002

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The purpose of this study was to investigate the factors affecting somatic cell counts (SCC) and milk composition of Chinese Holstein cows in Ningxia. The correlation of 198 855 measurements of the dairy herd improvement (DHI) data of 19 020 Chinese Holstein dairy cows (from 2009 to 2018) from 7 different dairy farms was analyzed using Minitab software. The results showed that 1) SCC was significantly correlated with farm, year and parity (P < 0.05); 2) SCC fluctuated with season and calving month, and decreased first and then increased with increasing lactation length; and 3) there were significant correlations between SCC and milk yield, milk fat percentage, milk protein percentage, milk sugar percentage and dry matter percentage (P < 0.05). Moreover, SSC, milk yield and the major milk components were influenced by environmental factors (farm, year and season) and cow’s own factors (parity, calving season and lactation period). In summary, fine management is an effective avenue to improve milk production and quality.

Processing Technology

Optimization of Fermentation Medium for Production of Glutamine Synthetase by Lactobacillus plantarum Lp-G18

XU Yu, JIANG Deyi, HAN Di

2019, 42(2):  13-17.  DOI: 10.15922/j.cnki.jdst.2019.02.003

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Lactobacillus plantarum is a probiotic bacterium with various biological effects. Its ability to relieve muscle fatigue and injury has aroused market concerns, which is associated with glutamine synthetase (GS) activity. However, the literature currently lacks reports on the production of GS by fermentation with Lactobacillus plantarum. In this study, the GS activity of L. plantarum Lp-G18 was enhanced by adding L-glutamic acid to the medium and optimizing the carbon sources and metal ion concentrations. The optimized medium was composed of glucose 40 g/L (222 mmol/L), MgSO4·7H2O 4.92 g/L (20 mmol/L), MnSO4 0. 025 g/L (1.5 mmol/L), L-glutamic acid 8.82 g/L (60 mmol/L), peptone 10 g/L, beef extract powder 10 g/L, yeast extract powder 5 g/L, K2HPO4 2 g/L, NaAc 5 g/L, diammonium hydrogen citrate 2 g/L, and Tween-80 1 g/L. The GS activity obtained using the optimized medium was 2.4 times higher than that from basal MRS medium.

Analysis & Detection

Determination of Galactooligosaccharides in Milk Powder by Ion Chromatography

WEN Guoyan, ZHAO Zhen, WAN Peng, ZHANG Lijun, CHEN Xirong, MENG Genhua, LI Cuizhi, Lü Zhiyong

2019, 42(2):  18-22.  DOI: 10.15922/j.cnki.jdst.2019.02.004

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In this paper, an ion chromatography method for the determination of galactooligosaccharides (GOS) in milk powder was established. The protein in the sample was precipitated by acetonitrile, and GOS was extracted with acetonitrilewater and purified using a C18 column (or RP column) to remove impurities. The analyte was separated using an ion chromatograph equipped with quaternary gradient pumps and detected with a pulse amperometric detector. The calibration curve of this method had good linearity in the range of 10–300 μg/mL, and the results from repeated sample measurements were stable. The recovery rates from blank samples spiked at levels of 500–2 000 mg/100 g were 82.1%–98.0%. To sum up, this method required simple sample pretreatment and gave accurate results, and it could be suitable for the determination of the GOS content in milk powder samples.

Reviews

Recent Progress in the Adsorption of Heavy Metals by Lactic Acid Bacteria

LIU Shaoli, YANG Zhennai

2019, 42(2):  23-27.  DOI: 10.15922/j.cnki.jdst.2019.02.005

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Heavy metal pollution is increasingly damaging the ecology. Furthermore, the enrichment of heavy metals through the food chain threatens human health. Therefore, the removal of heavy metals plays a vital role in maintaining ecological balance and protecting human health. Lactic acid bacteria have the ability of adsorbing heavy metals and are safe in bioremediation of heavy metal pollution. This review summarizes the current situation of research on lactic acid bacteria adsorption of heavy metals, which hopes to provide useful information for researchers in this field.

Recent Progress in the Application of Enterobacterial Repetitive Intergenic Consensus-Polymerase Chain Reaction Fingerprinting Technology in Bacterial Typing

HOU Xiaxia, WANG Yunxia, HU Xue, Lü Zhiyong, LIU Lijun, LI Cuizhi

2019, 42(2):  28-34.  DOI: 10.15922/j.cnki.jdst.2019.02.006

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Enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) allows gene amplification using primers designed based on ERIC, which are widely present in living organisms, yielding products that are useful to characterize the genomic structure. This method has been widely used in bacterial classification and research on the genetic relationship of strains because of its merits such as simplicity, ease of implementation, good repeatability and time saving. This paper reviews the background to bacterial classification research and the principle and characteristics of ERIC-PCR technique, and summarizes the advantages and disadvantages of ERIC-PCR technique in bacterial genotyping and recent progress in its application to genotype common food-borne pathogenic bacteria. At the same time, future prospects for the application of ERIC-PCR in traceability analysis of microbial contaminants in dairy enterprises.

Comparative of Worldwide Latest Standards for Pasteurized Milk

WEI Xinxin, PAN Hong, ZHAO Guangsheng, XIONG Wang, XIAO Shujun, GONG Jinyan, XIAO Gongnian

2019, 42(2):  35-39.  DOI: 10.15922/j.cnki.jdst.2019.02.007

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Milk and dairy products are high-quality foods that are often an excellent source of intact protein and important minerals. However, high nutrients and low acidity make milk a great medium for microbial growth. Heat treatment of milk is a key control point for killing pathogenic microorganisms, but it also causes the destruction of important nutrients. Pasteurization is a mild heat treatment that maximally preserves milk quality while killing pathogens. Currently, alkaline phosphatase activity is widely used to ensure the sufficiency of milk pasteurization. This paper reviews some of the worldwide latest standards for pasteurized milk. We compare and analyze the pasteurized milk standards in China and other major dairy producers like the United States, European countries and Australia. To conclude this review, we present some suggestions for improving China’s pasteurized milk standards.

Development of the Brown Yogurt Industry in Gansu Province: Present Situation and Existing Problems

LI Yiheng, WANG Ying, WANG Qihui, LI Xiaojiao, ZHU Yanli, JIAO Yaoyao, MA Ruijuan, WENG Pengcheng

2019, 42(2):  40-44.  DOI: 10.15922/j.cnki.jdst.2019.02.008

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Brown yogurt is a new type of yogurt with a burned flavor formed by the nonenzymatic Maillard reaction and silky smooth mouthfeel that contains high-quality nutrients and has become a new hotspot in the yogurt market. As Gansu province is one of the major livestock production areas and dairy processing bases in China, this region is bound to development the brown yogurt industry and seize market share. This article reviews the current status of the development of Gansu’s brown yogurt industry and existing problems. This review covers a summary of the history of the development of this industry and the problems encountered during the development process, the barriers to and driving forces for the research and development of brown yoghurt, the current status and challenges of brown yogurt processing, and the current trends and future prospects of brown yogurt.

Progress of Polymorphism of β-casein in Milk and Its Relationship with Human Health

LIANG Jie, GENG Xiaohui, LIU Yanping, YIN Chenyin

2019, 42(2):  45-49.  DOI: 10.15922/j.cnki.jdst.2019.02.009

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As a high-quality, nutritious food, milk is widely loved by people. β-casein is an important protein component in milk and is one of the indicators for evaluating the quality of milk. It plays an important role in protecting human health. As there are many varieties of β-casein in milk, it is of great significance to define the role of each β-casein. The most common variants of β-casein in milk are A1 and A2, while the other types are rare. Therefore, the current research regarding cow milk β-casein mainly focuses on these two variants. In this paper, the varieties and allele frequency of milk β-casein and its relationship with human health are elucidated. Recent progress in studying β-casein in milk is reviewed in order to provide readers with insights into milk β-casein.

Recent Advances in Goat Milk as a Milk Source for Infant Formula

MA Yuqin, SONG Li, CUI Guangzhi, SU Deliang, LI Yaping, ZHANG Lanwei

2019, 42(2):  50-54.  DOI: 10.15922/j.cnki.jdst.2019.02.010

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Goat milk is rich in a wide variety of nutrients and has prominent nutritional and functional properties. Because of its nutritional similarity to breast milk, goat milk is an emerging alternative milk source for infant formula to bovine milk. Nowadays, there is a worldwide interest in the safety and nutritional value of goat milk products. This article presents a discussion of the nutritional composition, safety and functional characteristics of goat milk, indicating that goat milk has great advantages for use as a milk source for infant formula. Goat milk is rich in a variety of nutrients including protein, fat, carbohydrates, vitamins and minerals and contains active substances such as superoxide dismutase and epithelial cell growth factors, protecting against viruses and tuberculosis infection with good safety. Infant formula made from goat milk has a reduced allergenicity and increased digestibility, and can enhance fat absorption rate and lower cholesterol levels.