Table of Content

01 November 2020, Volume 43 Issue 6

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Basic Research

Isolation and Identification of Lactic Acid Bacteria from Traditional Paraguayan Fermented Milk

SU Xin, YUAN Jing, LIU Qing, GUO Lin, LIU Wenjun

2020, 43(6):  1-6.  DOI: 10.15922/j.cnki.jdst.2020.06.001

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In order to enrich the resource of lactic acid bacteria and to systematically clarify the diversity of lactic acid bacteria in traditional Paraguayan fermented dairy products, lactic acid bacterial strains were isolated, purified and identified from traditional Paraguayan fermented milk by combined use of the traditional pure culture method, 16S rRNA gene sequencing and phylogenetic analysis. A total of 79 strains were isolated from eight samples, which were identified to belong to seven species of four genera. Lactococcus lactis was found to be the dominant strain, accounting for 68.35% of the total isolates.

Processing Technology

Optimization of Fermentation Process and Formulation for Low-Sugar, High-Fiber Normal-Temperature Fermented Milk

SHANG Yina, MA Hairan, HU Jiajie, FENG Zhikuan, WU Xiuying

2020, 43(6):  7-13.  DOI: 10.15922/j.cnki.jdst.2020.06.002

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In this experiment, citrus fiber, beet fiber and agar were used to develop a low-sugar, high-fiber room-temperature fermented yogurt, and the texture and sensory quality of yogurt samples made with their combinations in different proportions were evaluated. Lactase and Sweety T-1, a mixed commercial starter culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were used to completely decompose lactose in milk to produce glucose with higher sweetness, thereby improving the sweetness of low-sugar yogurt. The results showed that adding 3% citrus fiber, 0.2% agar and 1% beet fiber imparted good stability and high sensory score to low-sugar, high-fiber room-temperature fermented yogurt. Raw milk was inoculated 200 U/L Sweety T-1 with the addition of 1 600 BLU/L lactase and without the addition of any sugar or sweetener and was fermented at 42 ℃. After 12 h, lactose was completely decomposed, producing 2.5% glucose.

Analysis & Detection

Simultaneous Detection of 11 Pesticide Residues in Milk by High Performance Liquid Chromatography-Tandem Mass Spectrometry

XIA Weidong, QI Xiaoru, SU Yuncong, BAI Xiaoyun, LI Fei, LI Xingjia, DU Liwei, ZHANG Yaoguang, CHAI Yanbing

2020, 43(6):  14-19.  DOI: 10.15922/j.cnki.jdst.2020.06.003

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In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was proposed to simultaneously detect multiple pesticide residues in milk. The sample was extracted with acetonitrile, and partitioned by adding sodium chloride and magnesium sulfate. The extraction was carried out twice, and then the extract was purified with a C18 solid phase extraction column. Finally, the eluate was collected and evaporated to dryness after rotary evaporation, and the resulting residue was redissolved prior to instrumental analysis. The chromatographic separation was performed on a C18 column using gradient elution with a mobile phase consisting of 5 mmol/L ammonium acetate (containing 0.1% formic acid) and methanol. The detection was conducted using an electrospray ionization source under the multireaction monitoring (MRM) mode. The results showed that the calibration curves for acetamiprid, aldicarb, clothianidin, methamidophos, novaluron, fenbutatin-oxide, spirodiclofen, difenoconazole, cycloxydim, metaflumizone and 2-methyl- 4-chloro-phenoxyacetic acid (MCPA) had a good linearity in the concentration range of 0–100 ng/mL with correlation coefficients (R2) all greater than 0.995 0. The average recoveries for blank milk samples at three spiked concentration levels (1, 2 and 4 μg/L) were 40.2%–99.2%, with relative standard deviation (RSD) less than 18.9%, and the detection limit of the method was 1.00 μg/L. This method could allow quick and sensitive analysis of the contents of 11 pesticide residues in milk.

An Improved Ion Chromatography Method for Determination of Nitrite and Nitrate Contents in Milk and Milk Products

WU Lunwei, HU Xue, DUAN Guoxia, TANG Shuo, CHEN Jing, LIU Chunxia, GONG Huili, REN Yuju, LIU Lijun, LI Cuizhi

2020, 43(6):  20-25.  DOI: 10.15922/j.cnki.jdst.2020.06.004

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In order to develop a new method to determine nitrite and nitrate in milk and milk products, some improvements were made on the ion chromatography method specified in the national standard GB 5009.33-2016 Determination of Nitrite and Nitrate in Food. Samples were extracted with ultra-pure water and added with acetic acid to precipitate proteins before being chromatographed on AS11-HC column and detected with a conductivity detector. Under the above conditions, the calibration curves for nitrite and nitrate were linear with correlation coefficients greater than 0.99. The limit of quantitation (LOQ) for nitrite and nitrate was 0.25 and 0.8 mg/kg in milk, and 1 and 5 mg/kg in milk powder, respectively. The recoveries for spiked samples of milk powder and milk were from 80% to 110%. The improved method was simple to operate and cheap with ideal recovery and high precision. It could avoid potential problems encountered in the use of the traditional method and allow for more rapid and accurate detection of low contents of nitrite and nitrate in milk and milk products.

Reviews

Recent Progress in the Alleviating Effect of Bifidobacteria on Functional Constipation

LI Mengyang, MENG Yuan, SUN Qingshen, GE Jie

2020, 43(6):  26-30.  DOI: 10.15922/j.cnki.jdst.2020.06.005

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Functional constipation is a clinically common digestive system syndrome, which can cause a series of diseases. Therefore the prevention and treatment of this disease is of great significance. Bifidobacterium is one of the inherent flora in the human intestinal tract, which has been proved to have a significant alleviating effect on functional constipation. This review discussed the recent progress in understanding the alleviating effect of Bifidobacterium on functional constipation with respect to the relationship between the intestinal microbiota and functional constipation, the mechanism of Bifidobacterium in alleviating constipation and the efficacy of various Bifidobacterium strains, in order to provide research ideas for the in-depth development of functional Bifidobacteria strains and for understanding their mechanism in alleviating constipation.

Recent Progress in Preparation of Oligopeptides with High F Value from Milk Proteins

QIN Yusi, CHENG Ming, CHEN Pinghua, MI Xiaolei, WANG Cunfang

2020, 43(6):  31-35.  DOI: 10.15922/j.cnki.jdst.2020.06.006

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Milk proteins are high-quality proteins, mainly consisting of whey proteins and caseins. In whey proteins, branched-chain amino acids are 2.7 times more abundant than aromatic amino acids. Antioxidant peptides can be produced in large quantity from the hydrolysis of caseins. The main milk proteins, with well-balanced amino acid composition, show great promise as a source of bioactive peptides. In this paper, we review the state of the art in the preparation of high F value oligopeptides and elucidate the feasibility of preparing high F value oligopeptides from milk proteins, in order to provide a theoretical basis for expand the source of high F value oligopeptides.

Recent Progress in Research on Bone-Strengthening Functional Components of Dairy Products

JIE Liang, SU Miya, JIA Hongxin, CHEN Wenliang, QI Xiaoyan

2020, 43(6):  36-40.  DOI: 10.15922/j.cnki.jdst.2020.06.007

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Human bone growth peaks in adulthood after going through infancy, childhood and adolescence. Maximization of bone mass increment before adulthood and paying attention to bone health in middle and old age are important measures to prevent osteoporosis. Dairy products are an important source of nutrients for bone health, especially those fortified with bioactive substances beneficial for bone health for different populations. In this paper, the bioactive substances used in dairy products to strengthen bones are summarized, and the relationship between consumption of fortified dairy products and bone health in middle-aged and elderly people is reviewed.

A Literature Review on the Application of QuEChERS for Detection of Pesticide Residues in Dairy Products

HU Xue, LIANG Jianying, XIE Ruilong, ZHANG Zhiwei, LIU Lijun, LI Cuizhi, LüZhiyong

2020, 43(6):  41-45.  DOI: 10.15922/j.cnki.jdst.2020.06.008

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The detection of pesticide residues in dairy products is an important measure to ensure the quality and safety of dairy products. Currently, QuEChERS (quick, easy, cheap, effective, rugged, safe) is widely used as a sample pretreatment for all existing methods specified in the national standards for the detection of pesticide residues in dairy products. In this paper, we review these methods with a special focus on the principle and advantages of QuEChERS as well as its application in the detection of pesticide residues in dairy products.

Progress in the Development of Growth-Promoting Materials for Lactic Acid Bacteria

ZHENG Huajie, WANG Qingyun, WANG Xin, WANG Zhandong

2020, 43(6):  46-50.  DOI: 10.15922/j.cnki.jdst.2020.06.009

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Lactic acid bacteria have commonly been used in fermented foods, which will exert health-beneficial functions only when reaching a certain population level. Some lactic acid bacteria have strict requirements on growth conditions, making it difficult for many fermented products to ensure a high number of viable bacteria within the shelf life. How to promote the proliferation of lactic acid bacteria and maintain its stability has become a research hotspot. This paper reviews the roles of functional oligosaccharides, polysaccharides, whey protein hydrolysate and plant-derived materials in promoting the growth of lactic acid bacteria. It has been demonstrated that some growth-promoting materials are useful for promoting high-density culture of lactic acid bacteria, ensuring a high number of viable cells in fermented dairy products during storage, and improving the functions of probiotic products.

Dairy Products Safety Supervision Risks and Effective Governance System Optimization in China's Megalopolises in the New Era

CHEN Hui, MA Sijing, YUAN Yanfang

2020, 43(6):  51-57.  DOI: 10.15922/j.cnki.jdst.2020.06.010

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A megalopolis is not only the main body of dairy production and consumption, but also the main area where dairy safety supervision risks exist. At present, some risks exist in the production of raw materials for dairy products such as attaching more importance to safety than quality, and in the procedures of deep processing and circulation such as excessive processing, storage and hygiene issues during transportation; some problems exist in the field of dairy products safety supervision such as insufficient exertion of government functions and inadequate participation of social supervision. In order to defuse dairy products safety supervision risks and achieve effective governance of dairy production, it is needed to strengthen supervision over all processing steps of raw materials so as to provide guarantee for raw material quality construction, construct a sound and perfect quality evaluation and traceability system for deep processing and circulation, and to implement precision and standardized government supervision for supervision measures construction, and create conditions for social sharing and co-governance.