Table of Content

30 August 2015, Volume 38 Issue 4

Previous Issue    Next Issue

Basic Research

Effect of Dietary Nano Selenium on Selenium Level of Cow's Milk

PANG Kun, JIANG Lili, CHEN Gang, CHEN Yunlong, HAO Jingwen, HAN Liqiang

2015, 38(4):  1-3.  DOI: 10.15922/j.cnki.jdst.2015.04.001

Asbtract ( )   HTML ( )   PDF (1226KB) ( )  

Related Articles | Metrics

To investigate the effect of dietary nano selenium (Se) on the level of Se in cow’s milk, ten healthy Holstein dairy cows were divided into two groups of 5 animals each, i.e., control and test groups. The control group was fed a basal diet and the test group was additionally given 15 g of dietary nano selenium each day for each cow. The results indicated that despite having no significant effect on the contents of milk fat, protein and lactose (P > 0.05), dietary nano selenium significantly increased the level of Se concentration compared with (P < 0.05). The concentration of milk Se was increased gradually with prolonged dietary supplementation, reaching 29.4 μg/L on day 30 compared to only 16.6 μg/L for the control group (P < 0.05). From these results it can be concluded that dietary supplementation with nano-Se could increase the concentration of Se in milk.

Processing Technology

Optimization of the Formulation of a Dairy Beverage Containing Defatted Corn Germ Protein

XU Yujuan, LI Na, WANG Dawei

2015, 38(4):  4-8.  DOI: 10.15922/j.cnki.jdst.2015.04.002

Asbtract ( )   HTML ( )   PDF (1713KB) ( )  

Related Articles | Metrics

In this study, corn germ meal was defatted by supercritical CO2 fluid extraction and applied for the production of a composite dairy beverage. The optimization of dairy beverage formulations for improved stability and sensory quality was carried out using combination of single factor and orthogonal array experiments. The results showed that the optimal formulation consisted of 3% of defatted corn germ, 0.2% of citric acid, 0.25% of compound stabilizer, 2.5% of milk powder, and 10% of soft white sugar. The obtained beverage was characterized by homogenous texture, unique flavor, soft and delicate taste, a good balance of sweet and sour, and good stability.

Development of Yogurt Supplemented with Roselle

YU Ping, ZHANG Hongju

2015, 38(4):  9-13.  DOI: 10.15922/j.cnki.jdst.2015.04.003

Asbtract ( )   HTML ( )   PDF (1970KB) ( )  

Related Articles | Metrics

This study aimed to determine, using single factor experiments and orthogonal array design, an optimal roselle-supplemented yoghurt formulation when a stabilizer composed of gellan gum, agar and locust bean gum was used. It was shown that the best thickener concentrations were 0.04, 0.04 and 0.02 g/100 g for gellan gum, agar and locust bean gum, respectively. The best concentrations of roselle powder, stabilizer and sugar were 0.3, 0.6 and 8.0 g/100 g, respectively. Roselle powder was suspended in distilled water, adjusted to pH 5.5 in order to protect the stability of red pigments from roselle, and then added to the raw milk before fermentation.

Package & Storage

Effect of Milk Components on the Storage Quality of Set-Type Yoghurt

REN Jianghong, LI Longzhu, QIN Lihu, WANG Pan

2015, 38(4):  14-17.  DOI: 10.15922/j.cnki.jdst.2015.04.004

Asbtract ( )   HTML ( )   PDF (1603KB) ( )  

Related Articles | Metrics

Significant variations in components of fresh milk with season, temperature, and milking time and frequency lead to large differences in yogurt quality. In this paper, the influence of the contents of milk protein, fat and lactose on water retention and acidity of yogurt during storage was studied. The results showed that the water-holding capacity of yoghourt stored at 4 ℃ was apparently enhanced with increasing addition of milk protein, fat and lactose contents. Moreover, the acidity of yogurt was increased significantly with increasing addition of milk protein content, but was not significantly affected by the amount of fat or lactose.

Analysis & Detection

Establishment and Evaluation of Real-Time Fluorescence Quantitative PCR Method for Mycobacterium tuberculosis in Milk and Dairy Products

ZHANG Chenxi, LIU Zhao, PAN Wei, JIA Yun, WU Bin

2015, 38(4):  18-20.  DOI: 10.15922/j.cnki.jdst.2015.04.005

Asbtract ( )   HTML ( )   PDF (1611KB) ( )  

Related Articles | Metrics

A real-time fluorescence quantitative polymerase chain reaction (PCR) method was established for the rapid detection of Mycobacterium tuberculosis in milk and dairy products. According to the conserved sequence of Mycobacterium tuberculosis, specific primers were designed for establishing the PCR assay. The methodology was validated with respect to sensitivity, specificity and repeatability. The standard curve of the real-time PCR method had a good linear relationship with a correlation coefficient (R2) of 0.998 0, and its equation was fitted as y = ? 3.29x + 38.6. This method had a high sensitivity of 1 × 102 copies/μL and high anti-interference capacity, gave specific amplification curves for Mycobacterium tuberculosis and exhibited good repeatability. The intra- and inter-assay coefficients of variation (CV) obtained with varied concentrations of the standard plasmid were both smaller than 1%. To conclude, the real-time PCR method allows fast and accurate detection of Mycobacterium tuberculosis in milk and dairy products.

Reviews

Review on Protocooperation between Lactobacillus delbrueckii subsp.bulgaricus and Streptococcus thermophilus

ZHAO Chunyu, QU Xiaojun, CUI Yanhua, XU Tingting

2015, 38(4):  21-24.  DOI: 10.15922/j.cnki.jdst.2015.04.006

Asbtract ( )   HTML ( )   PDF (1233KB) ( )  

Related Articles | Metrics

The protocooperation mechanisms of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilusis is of great importance to the fermentation of milk, especially to bacterial adaptability to in acid environment. This paper discusses the symbiosismechanisms of the two strains from the following perspectives: two-component signal transduction systems, horizontal gene transfer, protein metabolism, nucleotide base metabolism, oxidative stress and carbon source metabolism, aiming to provide valuable references for further investigations on improving the quality of fermented milk products.

Development of Chymosin and Its Application in Cheese Production

ZHU Yuying, WANG Cunfang

2015, 38(4):  25-28.  DOI: 10.15922/j.cnki.jdst.2015.04.007

Asbtract ( )   HTML ( )   PDF (1216KB) ( )  

Related Articles | Metrics

With the rapid development of dairy industry in China, a growing deal of attention has been paid to the production of cheese. Chymosin plays an important role as a key enzyme in the process of cheese production, and it is an inevitable trend for chymosin to be the focus of future development in China. This paper briefly describes the types, structure, general characteristics and curding mechanism of chymosin and summarizes the different rennets used in cheese production. Future prospects of rennet are also discussed .

Microbial Risk Assessment for Safety of Dairy Products

LIU Jing, YOU Chunping, LIU Zhenmin, GUO Benheng

2015, 38(4):  29-33.  DOI: 10.15922/j.cnki.jdst.2015.04.008

Asbtract ( )   HTML ( )   PDF (1418KB) ( )  

Related Articles | Metrics

The safety of dairy products has increasingly become the focus of both social and scientific attention. This article provides an overview of the concepts of dairy product safety and microbial risk assessment. From the point of view of the hazard factors affecting the safety of dairy products, a comprehensive review is executed with respect to the sources of microbial hazards and the current status of microbial risk assessment at home and abroad. And differences between microbial risk assessment and chemical hazard risk assessment are pointed out. Finally, a perspective outlook is proposed to expect the future direction of microbial risk assessment of dairy products in China.