Table of Content

01 January 2017, Volume 40 Issue 1

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Basic Research

Biodiversity of Psychrotrophic Bacteria Isolated from Raw Milk and Their Enzymatic Profiles

XU Yu, LIU Zhenmin, YOU Chunping

2017, 40(1):  1-8.  DOI: 10.15922/j.cnki.jdst.2017.01.001

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Psychrotrophic bacteria and their heat-resistant enzymes are common contaminants in raw milk,leading to dairy product spoilage.The biodiversity of psychrotrophic bacteria isolated from raw milk in Shanghai was investigated by 16S rRNA sequencing and the individual isolates were evaluated for protease and lipase activities by plate culture.All isolates were classified into 33 genera in 9 classes,with Pseudomonas (55％),Acinetobacter (10％) and Flavobacterium (5％) being predominant,and the remaining 30 genera accounting for 30％ of the total number of isolates.Most isolates had the ability to produce protease or lipase,and different genera had different enzymatic profiles.Pseudomonas and Flavobacterium exhibited considerable protease activity,whereas Klebsiella showed strong lipase activity.On the other hand,most Acinetobacter isolates could produced neither protease nor lipase.

Analysis & Detection

High Performance Liquid Chromatography Determination of Abamectin Residues in Dairy Products and Feed

YUE Hong, LIU Yang, ZHAO Zhen, LIU Lijun, LI Cuizhi, SHAO Jianbo

2017, 40(1):  9-12.  DOI: 10.15922/j.cnki.jdst.2017.01.002

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A method for the determination of abamectin residues in dairy products and feed by using high performance liquid chromatography (HPLC) with fluorescence detection after precolumn derivation with trifluoroacetic anhydride and N-methyl imidazole was developed.Abamectin residues were extracted with acetonitrile,cleaned up on a tC18 solid phase extraction cartridge.After precolumn derivatization,the separation was performed on C18 column by gradient elution with methano-acetonitrile-water as mobile phase.The analyte were detected with a fluorescence detector and quantified by an external standard method.The recovery of abamectins spiked into milk powder at 1.5 μg/1 000 g (or 1 000 mL for milk) was higher than 90％.The limit of quantitation was 2 μg/kg for dairy products and 10.0 μg/kg for feed.This method proved to be accurate,simple reproducible,and suitable for the analysis of abamectin residues in dairy products and feed.

Detection of Sulfadiazine in Milk Using Surface Plasmon Resonance

ZHANG Teng, ZHAI Junhui

2017, 40(1):  13-15.  DOI: 10.15922/j.cnki.jdst.2017.01.003

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Surface plasmon resonance (SPR) was used to detect sulfadiazine (SD) in milk.SD-BSA conjugate as sensitive probe was immobilized onto the surface of a biochip for the development of a competitive inhibition immunoassay to detect SD in milk using SPR.The calibration curve was established.The limit of detection for SD was 3.41 ng/mL,and the recovery of spiked samples was in the range of 71％-120％.The proposed SPR method proved to be sensitive and accurate.

High Performance Liquid Chromatography Determination of Sucralose in Dairy Products

ZHAO Zhen, LIU Lijun, LI Suqin, YUE Hong, LI Cuizhi, SHAO Jianbo

2017, 40(1):  16-18.  DOI: 10.15922/j.cnki.jdst.2017.01.004

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A method for the determination of sucralose in dairy products by high performance liquid chromatography (HPLC) was developed.Samples were deproteinized by adding lead acetate followed by cleanup on an Oasis HLB solid-phase extraction cartridge.The separation was performed on a C18 column with 15％ acetonitrile in water as the mobile phase,and the analyte was detected with an evaporative light-scattering detector (ELSD) detector.The recovery of sucralose at spiked concentration levels of 7.5-70 mg/kg was 94.6％-101.3％.The limit of quantitation at a signal-to-noise ratio of 10 was 7.5 mg/kg.This method proved to be accurate,simple and suitable for the analysis of sucralose in dairy products.

A Comparative Study of the Determination of Lactulose in Ultra High Temperature Sterilized Milk Using High Performance Liquid Chromatography with Evaporative Light-Scattering Detector and Enzymatic Hydrolysis

LIU Yang, YUE Hong, ZHAO Zhen, LIU Lijun, LI Cuizhi, SHAO Jianbo

2017, 40(1):  19-22.  DOI: 10.15922/j.cnki.jdst.2017.01.005

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An analytical method to determine lactulose in ultra high temperature (UHT) sterilized milk by liquid chromatographic separation,evaporative light-scattering detection and external standard quantitation is described in this paper.After the protein was precipitated by adding hydrochloric acid,the separation was performed with satisfactory results on a NH2 column using 75％ acetonitrile in water as the mobile phase.The precision expressed as relative standard deviation (n =6) was 0.77％,and the average recovery was in the range of 98.7％-102.6％.This method was simpler and less time consuming with good repeatability than traditional enzymatic hydrolysis method.It can provide an alternative way of determining lactulose in UHT sterilized milk.

Reviews

Analysis of Australia's Dairy Food Safety Management System

WANG Cunhua, GONG Xiaoju

2017, 40(1):  23-27.  DOI: 10.15922/j.cnki.jdst.2017.01.006

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In recent years,the rapid development of dairy industry has highlighted its growing importance in the national economy of our country.As the quality and safety of dairy food is the lifeblood of the dairy industry,dairy food safety problems will affect the development of the national economy.In recent years,the occurrence of dairy food safety incidents seriously affected the healthy development of market economy.Therefore,it is urgent to solve the problem of dairy food safety.Being relatively more perfect,Australia's dairy food safety management system is analyzed in this paper in order to put forward some suggestions to solve those problems restricting the healthy development of China's dairy industry.

Recent Progress on Probiotics in Prevention and Treatment of Rumen Acidosis

WU Jiang, YE Gengping, LIU Guanglei, TANG Xinren

2017, 40(1):  28-32.  DOI: 10.15922/j.cnki.jdst.2017.01.007

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Rumen acidosis is a severe digestive system disorder which causes a great harm to the health and production performance of food-producing animals.After entering the rumen,probiotics can stabilize the ruminal pH value by maintaining the balance of the microbial community in the rumen.In addition,probiotics can bring its immune function back to normal by stimulating the body,and alleviate the symptoms caused by acidosis.The current state-of-the-art of knowledge about gastric acidosis is reviewed in this paper.

Bacterial Exopolysaccharides and Their Application in Dairy Products

XU Jia, WU Zhengjun, WENG Xinchu, WANG Yi

2017, 40(1):  33-37.  DOI: 10.15922/j.cnki.jdst.2017.01.008

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In recent years,exopolysaccharides produced by food-grade bacteria has aroused great interest.worldwide.In addition to the biological effects on their producers themselves,bacterial exopolysaccharides are widely applied in the agricultural,food,pharmaceutic as well as chemical industries for their prominently biological activities and processing properties.In this paper,the roles of some bacterial exopolysaccharides in biofilm formation and their chemical structures and prospects for application are reviewed.Further investigation on bacterial exopolysaccharides is also suggested.