Table of Content

01 September 2019, Volume 42 Issue 5

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Basic Research

Effect of Rice Oil on Rheological Properties of Spread Processed Cheese

XU Hangrong, ZHENG Yuanrong, LIU Zhenmin

2019, 42(5):  1-3.  DOI: 10.15922/j.cnki.jdst.2019.05.001

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This work aimed to study the effect of rice oil addition on rheological properties of spread processed cheese. Spread processed cheeses were prepared from Cheddar cheese with different amounts of rice oil added, and their storage modulus (G’) and the loss modulus (G”) were measured at different oscillation frequencies. The critical temperatures (melting temperature) for viscoelasticity changes of the processed cheeses were observed and compared. The results showed that G’ and G” decreased with rice oil addition, and so did melting temperature. The greatest decrease in melting temperature (2.45 ℃) was observed with the addition of 25% or 50% rice oil. This led us to conclude that the addition of rice oil to spread processed cheese should be controlled at less than 50%.

Processing Technology

Enzymatic Preparation of Bovine Whey Protein Hydrolysate with Low Allergenicity

LI Yan, YI Yang, SHI Jing, WANG Shijie, LUO Yongkang

2019, 42(5):  4-8.  DOI: 10.15922/j.cnki.jdst.2019.05.002

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Beta-lactoglobulin (β-LG) is one of the most important allergens in whey protein. How to reduce the antigenicity of β-LG is a problem that needs to be solved. In this paper, alkaline proteinase, trypsin or their combination was used to hydrolyze whey protein, and samples were taken at different hydrolysis times. The degree of hydrolysis and molecular mass distribution of the hydrolysate with the lowest antigenicity of β-LG were analyzed, and its bitter taste was compared with that of two commercial hydrolyzed whey protein products. Overall, hydrolysis of bovine whey protein with a mixture of alkaline protease and trypsin (1:1, m/m) produced products with low bitterness and antigenicity (0.798 μg/mL). The process parameters were as follows: substrate concentration 15 g/100 mL, enzyme to substrate ratio 5 000 U/g (50% alkaline protease plus 50% trypsin), initial pH 8.0, and hydrolysis for 2.5 h at 48 ℃.

Optimization of Medium Composition and Culture Conditions for Growth of Lactobacillus acidophilus LA-G80

CHEN Qi, MA Zhangxian, ZHENG Jianfeng, HAN Di

2019, 42(5):  9-15.  DOI: 10.15922/j.cnki.jdst.2019.05.003

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Lactobacillus acidophilus LA-G80, isolated from the human intestinal flora, has probiotic functions. In this study, the medium composition and culture conditions for this strain were optimized. The results obtained showed that the optimal medium consisted of glucose 41.5 g/L, maltose 20 g/L, soybean oligosaccharide 10 g/L, beef extract powder 18.64 g/L, tryptone 10 g/L, yeast peptone 15 g/L, Tween-80 1 mL/L, K2HPO4·7H2O 2 g/L, NaAc·3H2O 5 g/L, triammonium citrate 2 g/L, MgSO4·7H2O 0.25 g/L, MnSO4·4H2O 0.05 g/L, aspartic acid 0.16 g/L, alanine 0.16 g/L, serine 0.16 g/L, peanut protein powder 5 425 g/L, and soybean cake powder 7 425.48 g/L. The optimal culture conditions were as follows: inoculum size 2%, initial pH 6.0, constant pH 5.5, and constant temperature 37 ℃. Experiments carried out in a 5 L fermenter gave a viable cell count of 42.2 × 108 CFU/mL, which was about 10 times higher than that of observed with MRS medium.

Analysis & Detection

Isolation, Identification and Properties of Lactococcuslactis casei LC577 from Tibetan Kefir

QI Shihua, ZHANG Dong, ZHAO Linsen, AI Lianzhong, WANG Shijie

2019, 42(5):  16-20.  DOI: 10.15922/j.cnki.jdst.2019.05.004

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A probiotic lactic acid bacterium, named LC577, was isolated from Tibetan kefir. This bacterial strain was identified as Lactococcuslactis casei based on its morphologic properties, 16S rRNA sequence analysis and physiological and biochemical characteristics. The strain had a strong ability to produce acid, and produced a cheese-like aroma after fermentation in skim milk. In addition, it showed tolerance to acid and bile. After 4 h culture in a simulated gastric fluid, the viable count increased slightly, but decreased to 6.15 × 105 CFU/mL after exposed to 3 g/L oxgall for 4 h.

Determination of Casein Phosphopeptides in Powdered Formulae for Infants and Young Children by High Performance Liquid Chromatography

WEI Min, LI Xingjia, CHAI Yanbing, LI Fei, LIU Li, ZHANG Yaoguang

2019, 42(5):  21-24.  DOI: 10.15922/j.cnki.jdst.2019.05.005

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An analytical method was developed for the determination of casein phosphopeptides (CPP) in powdered formulae for infants and young children by high performance liquid chromatography. Three pretreatment methods and two operating conditions were optimized. The results showed that the optimal pretreatment conditions were as follows: transferring samples to a 50 mL volumetric flask after pH adjustment to 4.6 with 1 mol/L hydrochloric acid, and then filtering them through a filter paper. The chromatographic separation was carried out by gradient elution using 0.05% trifluoroacetic acid as mobile phase A and 0.05% acetonitrile as mobile phase B. The spiked recovery was between 94.50% and 95.45%, good linearity was observed with R2 = 0.999 8, and the detection limit was 2.0 mg/100 g. The method had the advantages of simple sample pretreatment as well as good stability and reliability, and the results from this method met the requirements in terms of linearity, recovery, accuracy, precision and detection limit. Thus it could be used to determine the content of CPP in powdered formulae for infants and young children.

Uncertainty Evaluation for the Determination of Aerobic Plate Count in Raw Milk

CUI Yan, XU Chuanpeng, QI Xin, XU Wenying, YAN Pingping, TIAN Zhuo, WANG Yu

2019, 42(5):  25-29.  DOI: 10.15922/j.cnki.jdst.2019.05.006

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The uncertainty in the determination of aerobic plate count in raw milk was evaluated and the feasibility of the uncertainty for judging the conformity of the test results. According to the two Chinese standards National Food Safety Standard Food Microbiological Examination: Aerobic Plate Count (GB 4789.2-2016) and Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1-2012), uncertainty evaluation was carried out on 10 batches of raw milk. The extended uncertainty for the 10 batches was 0.031 0-0.033 6 (lg(CFU/mL)). The established method could be used for uncertainty assessment of aerobic plate count detection in raw milk, and the obtained uncertainty could be used for assessing the quality of raw milk.

Reviews

Recent Progress in Understanding Functional Activities and Mechanisms of Action of Yogurt Fermented by Probiotics

XU Yu

2019, 42(5):  30-36.  DOI: 10.15922/j.cnki.jdst.2019.05.007

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Yogurt fermented by probiotics represents an important application of probiotics in the food field. In this paper, the recent progress in the study of yogurt fermented by probiotics is summarized, with a focus on the studies on its functional activities and mechanisms of action in the past five years. A large number of studies have shown the functional activities of yogurt fermented by probiotics including maintaining gastrointestinal, oral, and skin health; improving metabolism abnormalities like hypertension, hyperlipidemia, hyperglycemia, obesity and osteoporosis; regulating immune function like improving food allergy, relieving respiratory allergy, and elevating antioxidant capacity; and regulating mental and emotional functions. It is expected that this review will provide theoretical support for the development and research of fermented products with probiotics.

Recent Progress in Goat Milk Deodorization

REN Rong, WANG Bini, ZHANG Fuxin, ZHAO Aiqing, LIU Yufang

2019, 42(5):  37-41.  DOI: 10.15922/j.cnki.jdst.2019.05.008

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Goat milk is nutritious and easy to absorb, but its odor restricts the development of goat milk products and the goat milk industry. This paper provides a review of the odorant compounds of goat milk and their sources. Three techniques for the deodorization of goat milk, physical and chemical treatments and microbial fermentation are described and suggestions for this area of research are proposed. We hope that this review will provide an innovative basis for developing a new technique to deodorize goat milk and for goat milk fermentation.

Review on Detection Methods for Cephalosporins in Milk

LI Longfei

2019, 42(5):  42-45.  DOI: 10.15922/j.cnki.jdst.2019.05.009

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As broad-spectrum semi-synthetic antibiotics with strong antibacterial effect and little toxic side effects, cephalosporins are widely used in livestock and poultry farming, and the food safety risk arising from this is becoming the focus of public attention. At present many governments and food safety agencies have set maximum residue limits for cephalosporin residues in milk. This paper interprets the potential health risk of cephalosporin residues in milk, and summarizes recent progress in the development of pretreatment methods and detection technologies for cephalosporin residues in milk in detail.

A Review of Food Safety Risk Assessment from the Perspective of Marxist Philosophy

FANG Jun, CHEN Hui, YUAN Yanfang

2019, 42(5):  46-50.  DOI: 10.15922/j.cnki.jdst.2019.05.010

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This review presents an overview of the current food safety problems in China. From the perspective of Marxist philosophy, it systematically analyzes the three main sources of food safety risks in China and provides targeted suggestions. There are historical reasons for the current food safety risks, which occur in accordance with the law of social development. Overall, various food safety risks exist objectively at present, and there is still a big gap between the food safety level and people’s needs for a better life. Scientifically speaking, food safety does not represent absolute safety. There should be zero tolerance to any food safety problem, but we must admit that there is no zero risk food. We suggest that the capacity to manage food safety risks should be enhanced by adhering to the people-centered development thought, adhering to the thought on ecological civilization, practicing the core socialist values, adhering to scientific development and implementing social co-governance.