Table of Content

28 February 2013, Volume 36 Issue 1

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Basic Research

Use of Acetylated Crosslinked Starch as a Stabilizer for Set Yoghurt

LIU Xiao-ming, WANG Guan-qun, CUI Bo, TAN Cong-ping

2013, 36(1):  1-4.  DOI: 10.15922/j.cnki.jdst.2013.01.001

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This study investigated the effect of addition of acetylated crosslinked starch as a stabilizer on set yoghurt. The presence of acetylated crosslinked starch was effective in controlling the acidity of yoghurt and improving its water holding capacity and freeze-thaw stability; however, excess acetylated crosslinked starch caused in a reduction in flavor compounds, a rough taste and a lack of refreshingness. Addition of 0.5%–1.5% acetylated crosslinked starch in set yoghurt was preferred.

Change in Lactose Content during Mammary Gland Development of Holstein Cows

ZONG Can-hua, LI Qing-zhang

2013, 36(1):  5-7.  DOI: 10.15922/j.cnki.jdst.2013.01.002

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Objective: To explore the changing pattern of lactose content during mammary gland development of Holstein cows. Methods: High-performance liquid chromatography was used to determine lactose content. Results: Lactose was detectable in the mammary gland during the perinatal period, and showed an increasing trend during the lactation period, reaching a peak after 140 d of lactation, and then a dramatic decrease during the involution period, reaching a very low level after 30 d of involution. In conclusion, lactose content exhibits different levels in the mammary gland of Holstein cows during different physiological periods.

Processing Technology

Preparation of Sodium Alginate/Chitosan Synbiotic Microcapsules and Its Storage Stability and Controlled Release

LI Wei, JI Juan, CHEN Xiao-hong, JIANG Mei, RUI Xin, DONG Ming-sheng

2013, 36(1):  8-12.  DOI: 10.15922/j.cnki.jdst.2013.01.003

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In this study, sodium alginate and chitosan were used together to embed Streptococcus thermophilus in the presence of galactooligosaccharide (GOS) for the preparation of alginate/chitosan bilayer synbiotic microcapsules. The preparation process and the storage stability and controlled release of the resulting microcapsules were investigated. The bilayer synbiotic microcapsules prepared at a sodium alginate concentration of 2 g/100 mL had desired appearance, particle size and embedding rate and were found to be stable when exposed to simulated gastric fluid; however, complete disintegration of these microcapsules and consequent complete release of Streptococcus thermophilus were observed when the exposure time was up to 150 min. The survival rate of free Streptococcus thermophilus in suspensions with or without added GOS declined greatly after refrigerated storage, only 0.32% on the 13th day for Streptococcus thermophilus suspension in the absence of GOS compared to 14.64% for the presence of GOS. For bilayer synbiotic microcapsules, the bacterial survival rate descended only slightly during the entire storage period regardless of the presence or absence of GOS and remained as high as 93.64% and 87.98%, respectively.

Development of a Fermented Milk Product from Reconstituted Milk and Black Rice Hydrolysate

GUO Fei-xiang, HAN Qing-qing, GU Rui-xia, LU Mao-lin

2013, 36(1):  13-15.  DOI: 10.15922/j.cnki.jdst.2013.01.004

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A fermented milk product was developed based on simultaneous fermentation of reconstituted milk and black rice hydrolysate. The optimum saccharification conditions of black rice hydrolysate were found to be 60 ℃, 200 U/g and 7 h for temperature, enzyme loading and time, respectively. By using one-factor-at-a-time approach and orthogonal array design, the optimum fermentation conditions were determined as 5%, 20%, 3%, 40 ℃ and 4 h for sucrose concentration, black rice hydrolysate concentration, inoculum size, temperature and time, respectively. The resulting product had good quality and great potential for further development.

Analysis & Detection

Simultaneous Determination of Twelve Elements in Milk Powder for Infants and Young Children by Inductively Coupled Plasma Atomic Emission Spectrometry

YANG Yang, LU Jian, XU Chun-xiang, ZHANG Zheng

2013, 36(1):  16-18.  DOI: 10.15922/j.cnki.jdst.2013.01.005

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A method for the simultaneous determination of twelve elements (K, Ca, Na, Mg, Cu, Fe, Mn, Zn, Al, Pb, Cr and Cd) in milk powder for infants and young children by inductively coupled plasma atomic emission spectrometry (ICPAES) was established. Instrumental parameters were optimized. Standard curves for these twelve elements were obtained with correlation coefficients greater than 0.9995. The detection limits of the ICP-AES method for these elements were in the range of 0.02 to 5 mg/kg, and the spiked recoveries were 87.5%–106.3% with RSD lower than 5% (n = 6). This method was rapid and accurate and could be used for quality control and safety evaluation of milk powder.

Colloidal Gold-Based Immunochromatographic Assay for Rapid Detection of Casein

WANG Li-li, ZHOU Jian, LI Yan, SHU Wen-xiang

2013, 36(1):  19-21.  DOI: 10.15922/j.cnki.jdst.2013.01.006

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Objective: To develop a colloidal gold-based immunochromatographic assay for rapid detection of casein. Methods: We used casein and anti-casein polyclonal antibody as raw materials, nitrocellulose membrane and glass fiber paper as a carrier to prepare a rapid test strip. Results: The sensitivity of the test strip was 2.3 mg/mL, and the detection process required 10 min with good repeatability and stability. Conclusion: We have successfully developed a casein test strip.

Identification and Analysis of a Nontypical Staphylococcus aureus Strain

QIU De-yi, JIAN Zhi-hua, QIU Xia, XIAO Qi-qian, CAI Xian-quan, YUE Qiao-yun

2013, 36(1):  22-24.  DOI: 10.15922/j.cnki.jdst.2013.01.007

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A suspected strain isolated from a batch of processed dairy products submitted by an import/export enterprise to our laboratory for the detection of Staphylococcus aureus was identified and analyzed. According to the Chinese national food safety standard Food Microbiological Examination: Staphylococcus aureus (GB 4789.10–2010), sampling and enrichment were performed, the suspected colony isolated on BP plates was subjected to hemolysis test on blood agar plates, microscopic observation after Gram staining, and plasma coagulase test before alignment, analysis and confirmation using a fully automated bacterial identification system and PCR. The suspected strain had a larger colony diameter compared with the reference strain of Staphylococcus aureus, showed white colonies on blood agar plates with no obvious hemolysis phenomenon but positive plasma coagulase test results, and was identified using a fully automated bacterial identification system and PCR as a nontypical strain of Staphylococcus aureus. In conclusion, real-time PCR enables rapid and accurate detection of Staphylococcus aureus while substantially shortening the detection time, and the possibility of missing the pathogen can be effectively overcome by combined use of different detection methods.

Reviews

Nutritional Value and Current Research Status of Goat Milk

LIU Chang, XU Xiao-dan, SHI Yong-cui, WANG Cun-fang

2013, 36(1):  25-34.  DOI: 10.15922/j.cnki.jdst.2013.01.008

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Goat milk as an emerging source of milk has received increasing interest for its full range of nutrients and unique health benefits. In recent years, the health benefits of goat milk have been recognized in many different cultures and goat milk is considered to have more potential for development than bovine milk due to its better quality. This paper describes the nutritional value and health benefits of goat milk and highlights the current status of research on goat milk and goat milk products in China and foreign countries, aiming at providing references for further development of China’s goat milk industry.

Planning and Design of Dairy Farms in High-Temperature and High-Humidity Areas: Taking Huanggang, Hubei for Example

LI Ning, ZHU Ming-zhi

2013, 36(1):  29-31.  DOI: 10.15922/j.cnki.jdst.2013.01.009

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Nowadays, the dairy industry has gradually developed into large-scale production from the traditional mode. With expanding farming scale, construction of dairy farms in high temperature and high humidity areas is becoming increasingly important. The infrastructure conditions directly affect the milk quality and economical benefit of breeding and reproduction of cows. This paper analyzes the design of dairy farms based on site selection, building construction, ventilation, cooling and epidemic prevention, aiming to alleviate, to some extent, the negative impact on cow breeding of high temperature and high humidity so as to improve the breeding benefit.

Effect of Dietary Nucleotides on the Gastrointestinal Tract in Infants and Its Safety

ZHAO Hong-xia, HAO Wan-qing

2013, 36(1):  32-35.  DOI: 10.15922/j.cnki.jdst.2013.01.010

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This paper describes the effect of dietary nucleotides on the gastrointestinal tract in infants, the absorption and metabolism of nucleotides in the body, and makes a comparison of the nucleotide content of human milk and cow’s milk. Compared to breast milk, the contents of nucleotides and their derivatives in cow’s milk is lower, and can not meet an infant's nutritional requirements.

Research Progress in the Stability of Acidified Milk Systems

SONG Xiao, CUI Bo, TAN Cong-ping

2013, 36(1):  36-39.  DOI: 10.15922/j.cnki.jdst.2013.01.011

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Acidified milk systems are prone to whey syneresis, resulting in phase separation. This phenomenon can be prevented by stabilizer addition. This paper explains the mechanism underlying the role of hydrocolloids like pectin in stabilizing acidified milk systems, aiming at providing ideas for applications of more stabilizers in foods.