Table of Content

01 May 2016, Volume 39 Issue 3

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Basic Research

Acid and Bile Salt Tolerance of Exopolysaccharide-Producing Strains ofLactobacillus plantarum

ZHAO Xiaoxi, WEI Xudan, CHEN Dailing, GUAN Wen, FENG Meiqin

2016, 39(3):  1-3.  DOI: 10.15922/j.cnki.jdst.2016.03.001

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The probiotic effects of lactic acid bacteria (LAB) depend on their tolerance to the human gastro-intestinal tract. The acid and bile salt tolerance of four exopolysaccharide-producing strains of Lactobacillus plantarum was examined by the measurement of optical density at 600 nm (OD600 nm) and the plate colony counting. The results showed that the strain F401④ had higher acid tolerance capacity, and F201⑥ had the highest bile salt tolerance capacity which showed more than 100% survival rate after culture for 4 h in the presence of 0.3 and 0.5 g/100 mL bile salt.

Effects of Acid and Heat Treatments on Functional Properties of Yak Milk Caseins Separated by Microfiltration

WANG Guojiao, HANG Feng, HONG Qing

2016, 39(3):  4-8.  DOI: 10.15922/j.cnki.jdst.2016.03.002

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Caseins were separated from the fresh milk of grazing yak cows in Tianzhu county, Gansu province by microfiltration to investigate changes in their heat stability, hydrophobicity, particle sizes and molecular weights after different pH treatments (pH 6.4, 6.6, 6.8 and 7.0) and heat treatments (80, 100, 120 and 140 ℃). The results showed that functional properties of yak milk caseins at pH 6.8 revealed the most significant deterioration after each heat treatment. At a temperature far below the denaturing temperature the caseins exhibited good retention of functional properties. Both acid and heat treatments caused molecular polarization of the caseins, destroyed the hydrophobic force, which contributes to maintaining the spatial structure of the protein molecules, and accordingly induced their dissociation or aggregation, causing changes in their molecular structure and in turn affecting their functional properties.

Effects of Parity and Lactation Stage on Somatic Cell Score and Milk Production Loss in Dairy Cows

JIN Yadong, LI Yanyan, XU Xiaofeng

2016, 39(3):  9-13.  DOI: 10.15922/j.cnki.jdst.2016.03.003

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The aim of this study was to explore the effects of parity and lactation stage on somatic cell counts in dairy herd improvement (DHI) milk samples and milk production loss in dairy cows. The results indicated that the somatic cell score (SCS) was increased with parity, and SCSs at different stages of lactation performance in different parities were different. SCS was increased with lactation time in first-parity dairy cows and SCS values were significantly different at three lactation stages (P < 0.05). The same trend was observed for SCS in second- and third-parity cows; SCS was higher at the early lactation stage than at the middle lactation stage, and its values at the two stages were significantly lower than that at the late lactation stage (P < 0.05). Milk production loss in dairy cows generally rose with parity and was higher at the early and late stages of lactation than at the middle stage.

Rheological Properties of Matcha Milk Tea

HU Junrong, YANG Kai, LIU Xiaojie, PAN Yongming, JIANG Hubing, FENG Yuhong, OU Kai, WU Weidu

2016, 39(3):  14-17.  DOI: 10.15922/j.cnki.jdst.2016.03.004

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Matcha is currently used in a wide variety of food products as a healthy and fashionable food ingredient. However, matcha, a finely milled green tea powder, cannot be dissolved sufficiently in the system so that the problem of its suspension property in aqueous systems needs to be solved for its application in commercial beverages. This study was done to examine rheological properties of matcha milk tea blended with different proportions of microcrystalline cellulose (MCC) and carrageenan. It was demonstrated that the addition of MCC and carrageenan at levels of 0.3–0.4 and 2.7–3.0 g/L, respectively rendered the system stable with a viscosity of 5–7 mPa·s and thixotropic loop area of 4.31–4.47 Pa/s.

Processing Technology

Response Surface Optimization of Processing of Goat Milk Foam Containing Coarse Grain

ZHU Yuying, WANG Cunfang, WANG Jianmin

2016, 39(3):  18-24.  DOI: 10.15922/j.cnki.jdst.2016.03.005

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In this study, the formulation of roughage-containing goat milk foam as a health product using goat milk and corn flour as main ingredients were optimized based on sensory evaluation and hardness using response surface analysis. The results showed that optimum combination of ingredients were determined as follows: ratio of corn flour to goat milk (m/V), 0.435:1; ratio of xylitol to sucrose (m/m), 0.712:1; and sucrose ester, β-cyclodextrin, citric acid and gelatin at concentration levels of 0.18%, 2.8%, 0.095 8% and 1.994%, respectively. The dairy product had a smooth appearance, evenly distributed color and refreshing taste with moderate sourness, integrating the unique aromas of goat milk and corn. Its sensory score was up to 95.48 and its hardness was 371.95 g, suitable for the vast majority of consumers. Moreover, the product showed maximum retention of the nutrients and health-protecting ingredients.

Effect of Heat Treatment on Stability Characteristics of Buffalo Milk

WA Yunchao, ZHAO Haiqing, LI Renfang, LIU Yanjing, WU Yun, XIE Bingqiang, JIANG Xinrong, QU Hengxian, WANG Qin, ZHANG Qibo, YU Fan, REN Yuanqing, GU Ruixia

2016, 39(3):  25-28.  DOI: 10.15922/j.cnki.jdst.2016.03.006

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The objective of this study was to explore and compare the effect of different heat treatments on the stability of buffalo milk. For this purpose, milk samples were subjected to different heat treatments for the comparative determination of pH buffer capacity, total dissolved solids (TDS) content, the amount of protein precipitation and apparent viscosity. The results showed that the pH buffering capacity, TDS, protein precipitation and apparent viscosity of buffalo milk were significantly changed after heat treatments. After treatment at 121 ℃ for 15 min, the pH buffering capacity, TDS, protein precipitation and apparent viscosity reached their maximum levels, while pH buffering capacity and TDS were minimized after treatment at 95 ℃ for 5 min. Therefore, it was concluded that the stability of buffalo milk was most affected by treatments at 121℃ for 15 min and at 95 ℃ for 5 min in the experimental range investigated.

Reviews

Progress in Research on Mechanism of Action of Transglutaminase on Milk Proteins and Its Application

ZHANG Xuexi, WANG Cunfang, WANG Jianmin

2016, 39(3):  29-32.  DOI: 10.15922/j.cnki.jdst.2016.03.007

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As an enzyme that catalyzes the transfer of acyl groups, transglutaminase is widely used in the dairy industry. This paper briefly describes the source and catalytic mechanism of the enzyme, and further explains the mechanism of action of the enzyme on milk proteins, including casein, whey protein and milk protein products. Moreover, the application of the enzyme in the dairy industry is summarized in this paper.

Recent Progress and Current Status of Studies on Human Milk Oligosaccharides (HMOs) and Their Application in China

WEI Yuanan, ZHANG Lijun, ZHENG Huiling, CHEN Xiaolin

2016, 39(3):  33-38.  DOI: 10.15922/j.cnki.jdst.2016.03.008

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Human milk oligosaccharides (HMOs) are a group of complex glycans occurring in human breast milk that play important roles in the growth and development of infants. More than 200 distinct kinds of HMOs have been identified so far. The naturally occurring mixtures of HMOs in humans have different components and profiles that reflect the mother’s genetic makeup (e.g., Lewis blood type), duration of lactation, life style, diet and geographic region. A number of functions that may protect the health of breast-fed infants have been reviewed for HMOs. However, available information on the content and profiles of HMOs in human milk, especially among Chinese mothers, is limited. Therefore, further research on the relationship between the structure and functions of HMOs and a databank of HMOs from Chinese mothers are needed in order to establish a firm scientific basis and specific guidelines for improved infant formula in the future.

A Review on Methods Used for Aflatoxin M1 Detection in Milk

LI Longfei

2016, 39(3):  39-43.  DOI: 10.15922/j.cnki.jdst.2016.03.009

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Recently, food safety problems associated with milk have consistently occurred in the country and abroad. Aflatoxins, a class of highly toxic compounds widely occurring in milk, have attracted growing public attention. Aflatoxins, as well as being strongly carcinogenic, are also teratogenic and mutagenic, posing a tremendous threat to human and animal health. Aflatoxin M1, a metabolite of aflatoxin B1, is a common toxin present in milk. In this paper, the sources and harms of aflatoxin M1 in milk are outlined with focus on reviewing the current progress in the development of analytical methods for the detection of aflatoxin M1.