Table of Content

01 September 2021, Volume 44 Issue 5

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Basic Research

Comparative Study of Free Amino Acids and Insoluble-Proteome Amino Acids in Bovine Colostrum and Mature Milk

SONG Wanying, LI Mohan, ZHANG Xiumin, YANG Mei, YUE Xiqing, ZHENG Yan

2021, 44(5):  1-6.  DOI: 10.15922/j.cnki.jdst.2021.05.001

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Bovine milk is considered as the raw milk of choice for the production of infant formula. Amino acids in bovine milk, the structural units that make up milk proteins are classified into two groups: free and insoluble-proteome amino acids, which are distributed in different regions (structural domains). In this experiment, we collected bovine colostrum at 0–7 days postpartum and mature milk at 15 days-6 months postpartum for comparative analysis of the insoluble-proteome and free amino acids in them. The results indicated that 9 essential free amino acids and 7 non-essential free amino acids were detected in both milks. Additionally, another non-essential free amino acid was found in bovine colostrum. Among these, 8 essential and 4 non-essential amino acids were found to be significantly more abundant in bovine colostrum than in mature milk (P < 0.05). Among the insoluble-proteome amino acids, 8 essential amino acids and 10 non-essential amino acids were detected simultaneously in both milks. Moreover, the levels of threonine, arginine, serine, cysteine, alanine in bovine colostrum were significantly higher than in mature milk (P < 0.05), while the level of lysine was significantly lower than in mature milk (P < 0.05).

Nutrient Analysis of Milk Powder for Schoolchildren Sold in Chinese Markets

LIAO Weiyao, MENG Liping, WANG Yanbo, FU Linglin, HAN Junhua

2021, 44(5):  7-11.  DOI: 10.15922/j.cnki.jdst.2021.05.002

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This study aimed to analyze the nutritional fortification and the distribution of energy and nutrient contents of different brands of milk powder for schoolchildren sold in Chinese markets. The daily supply of energy and nutrients from each product was calculated according to the nutritional information and recommendations for consumption on the package, and compared with the amounts recommended by the Chinese dietary reference intakes (DRIs) for schoolchildren. The results showed that the contents of vitamin C, vitamin E, vitamin B6, folic acid, docosahexaenoic acid (DHA), dietary fiber and linoleic acid varied greatly among different brands of milk powder for schoolchildren. Vitamins A, D, C, taurine and the minerals calcium, iron and zinc were fortified in more than two-thirds of the investigated samples. Based on their median nutrient contents, the milk powders provided about 12% of the energy requirements of male schoolchildren at 7–10 of age, including about 30% of the protein, vitamin C, vitamin D and iron, about 40% of the vitamin B6, calcium and zinc, and nearly 50% of the vitamin A and vitamin B2. Overall, milk powder for schoolchildren, a convenient and easily available dairy product, has nutritional advantages.

Processing Technology

Process Optimization for Production of Freeze-Dried Cells of Bifidobacterim bifidum TMC3115

YANG Ling, ZHANG Dong, QI Shihua, MA Xinying, ZHOU Shuaikang, AI Lianzhong, WANG Shijie

2021, 44(5):  12-17.  DOI: 10.15922/j.cnki.jdst.2021.05.003

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In order to prepare lyophilized cells of Bifidobacterium bifidum TMC3115 with high viability, the impact of the initial pH of the medium, different carbon and nitrogen sources, and inoculum quantity on the viable cell count was studied by the one-factor-at-a-time method. Subsequently, an orthogonal array design was applied to optimize combinations of carbon and nitrogen sources based on the pH of the medium at 16 h of culture, cell density (expressed as optical density) and viable cell count. The efficacy of 18 cryoprotectants on the probiotic strain was investigated, and the optimization of cryoprotectant blends was carried out using an orthogonal array design. The results showed that when the initial medium pH was 7.2 and the inoculum amount was 4%, the viable cell count reached the highest. The optimized medium was composed of glucose 25 g/L, tryptone 20 g/L, yeast peptone 10 g/L, yeast extract FM902 15 g/L, diammonium citrate 2 g/L, anhydrous sodium acetate 5 g/L, dipotassium phosphate 2 g/L, Tween-80 1 g/L, magnesium sulfate 0.58 g/L, manganese sulfate 0.25 g/L, and L-cysteine hydrochloride 0.5 g/L. The optimal cryoprotectant was composed of skim milk 12%, trehalose 12%, glycerol 1.2%, sodium glutamate 0.6%, and L-cysteine hydrochloride 0.15%. The viable cell count of the freeze-dried culture produced under the optimized conditions reached 4.26 × 1011 CFU/g.

Effect of Fat Content on the Quality of Sliced Processed Cheese

HONG Qing

2021, 44(5):  18-22.  DOI: 10.15922/j.cnki.jdst.2021.05.004

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In this work, the effects of different fat contents and fat substitutes on the quality of processed cheese slices were studied. The physicochemical indexes, color, texture and sensory quality of five cheese samples with different fat contents were evaluated. The results showed that there were significant differences in pH value and the contents of protein and fat among cheeses. Addition of enzymatically hydrolyzed butter concentrate had a significant impact on the color parameters lightness (L*) , redness (a*) and yellowness (b*) of cheese. Texture profile analysis (TPA) parameters of 50% reduced-fat cheese with 100% substitution of butter by enzymatically hydrolyzed butter concentrate were different from those of the other cheeses. Compared with full-fat cheese, 25% reduced-fat cheese and 50% reduced-fat cheese with 50% reduction of butter, 50% reduced-fat cheese with 25% reduction of butter and addition of 5% enzymatically hydrolyzed butter concentrate did not significantly differ in any of the texture parameters except cohesiveness and resilience. Sensory evaluations showed that 50% reduced-fat cheese with 100% substitution of butter by 20% enzymatically hydrolyzed butter concentrate scored lowest. Compared with the reduced-fat cheese, 50% reduced-fat cheese with partial substitution of enzymatically hydrolyzed butter concentrate for butter showed improved flavor and taste and the overall sensory score was not significantly different from that of full-fat cheese. Accordingly, the quality of reduced-fat cheese slices can be improved by reducing butter content and adding enzymatically hydrolyzed butter concentrate.

Factors Affecting Lactoperoxidase Activity in Milk

HUA Bangqing

2021, 44(5):  23-26.  DOI: 10.15922/j.cnki.jdst.2021.05.005

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The activity of lactoperoxidase in milk is an important index of the extent of pasteurization heat treatment. Excessive heat treatment will obviously destroy the nutrition of milk, and also lead to the production of some undesirable substances. In this investigation, the activity of lactoperoxidase in milk subjected to different treatments was determined, and the effect of storage temperature and time on the enzyme activity was also explored. The results showed that low-temperature ceramic membrane filtration resulted in significantly lower loss of lactoperoxidase activity than did pasteurization treatment at 75 ℃ for 15 s. Excessive treatments also led to the loss of lactoperoxidase activity. Moreover, excessively high storage temperature led to a faster reduction of lactoperoxidase activity, and the enzyme activity gradually decreased with storage time. The activity of lactoperoxidase in raw milk decreased more rapidly than that in pasteurized milk during storage.

Analysis & Detection

Determination of 12 Organophosphorus and Carbamate Pesticide Residues in Soy Milk by Gas Chromatography-Tandem Mass Spectrometry

XIE Ruilong, LIANG Jianying

2021, 44(5):  27-31.  DOI: 10.15922/j.cnki.jdst.2021.05.006

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A method based on quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) for the simultaneous quantitative determination of 12 organophosphorus and carbamate pesticide residues in soy milk. The samples were extracted with acetonitrile, then the supernatant was separated after addition of citrate buffer, followed by cleanup with a mixture of anhydrous magnesium sulfate, primary secondary amine (PSA) and C18 sorbents. The analytes were detected by GC-MS/MS. The results showed that the limits of quantification (LOQs) were 0.004 mg/kg for the 12 pesticides. The calibration curves were linear in the concentration range of 5–200 ng/mL with correlation coefficient greater than 0.99. The recoveries varied from 71.8% to 114.9% with relative standard deviation (RSD) from 4.6% to 13.3% at three different spiked levels. The method was found to be quick, efficient, accurate and suitable for the determination of organophosphorus and carbamate pesticide residues in soy milk.

Reviews

A Review of the Application of Transcriptome Sequencing in Research on Bacteriocin Synthesis by Lactobacillus plantarum

ZHAO Le, MENG Xiangchen

2021, 44(5):  32-37.  DOI: 10.15922/j.cnki.jdst.2021.05.007

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Bacteriocin can be used as a natural non-toxic antibacterial agent in foods because of its resistance to foodborne pathogens and spoilage bacteria. Bioinformatics is a subject based on computer science and applied mathematics, which aims to locate the functional genes by searching for and comparing the biological information measured in the field of life science and analyzing the related nucleic acid information and structural protein genes. Transcriptomics aims to analyze all RNA transcribed by different cells or tissues under specific conditions at the overall transcriptional level, providing insights into biological pathways and molecular regulatory mechanisms. By comparing mass transcriptome sequencing data with the reference genome, the genetic information of transcripts can be quantitatively analyzed at the level of gene expression. Gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis can be used to speculate the functional characteristics of differentially expressed genes selected by differential expression folds and further understand the mechanism of the synthesis of bacteriocin and other metabolites. Transcriptome sequencing is a safe and economical technology that is expected to provide a new approach for the large-scale production of bacteriocins.

Nutritional Components of Human Milk and Their Role in Infant Development

JIE Liang, SU Miya

2021, 44(5):  38-42.  DOI: 10.15922/j.cnki.jdst.2021.05.008

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Early nutrition has an enormous influence on an infant’s physiological function, immune system maturation, and cognitive development. The special nutritional liquid of human milk is recognized as the gold standard for human infant nutrition and the best food. It can meet all the nutritional needs of infants within 6 months of age after birth. The World Health Organization (WHO) recommends exclusive breastfeeding for infants for the first 6 months of life. The relevant laws and regulations in China emphasize that breast milk is the most ideal natural food for infants and advocate exclusive breastfeeding for infants for at least 6 months after birth. The composition of human milk and its effect on infant development are comprehensively reviewed in this article, which is expected to provide a scientific basis for clarifying the nutritional needs of infants and establishing nutrition and health standards for infants.

Recent Advances in Processing and Quality Evaluation Technologies for Fermented Milk

Recent Advances in Processing and Quality Evaluation Technologies for Fermented Milk

2021, 44(5):  43-50.  DOI: 10.15922/j.cnki.jdst.2021.05.009

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Fermented milk is rich in protein, calcium and vitamins and contains a full range of nutrients, which is favored by the public due to its unique flavor. With the rapid development and application of new technologies, great progress has been made in the production, processing and quality evaluation of fermented milk. In this paper, we review recent progress in the development of new raw materials, starter cultures and production technologies for fermented milk as well as quality evaluation technologies including texture, flavor, nutrient and microbial quality analysis, omics technology and high-throughput sequencing technology. We expect this review to provide a theoretical basis for the production and quality detection of fermented milk in the future.

Review on Patented Techniques for 2’-Fucosyllactose Biosynthesis

LI Yunfei, LUAN Qingmin, LIU Feng, SUN Guilian, ZHANG Li, LI Zhenzhen, LI Kewen

2021, 44(5):  51-57.  DOI: 10.15922/j.cnki.jdst.2021.05.010

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Constructing an efficient and safe producer strain is a prerequisite for biosynthetic production of 2’-fucosyllactose. The number and technical content of recent patents on 2’-fucosyllactose biosynthesis applied for in China are reviewed in this paper, indicating that over 80 percent of the patents focused on the construction of recombinant strains by optimizing the metabolic pathways, overexpressing 2’-fucosyllactose biosynthesis-related enzyme genes, and developing more safe and efficient host strains. However, after a review of China’s patented technologies in this regard, we found that research on the biosynthetic production of 2’-fucosyllactose in a pilot scale or above is weak, and there is a lacuna in utility and industrially oriented patented technologies, which will bottleneck the 2’-fucosyllactose biosynthesis industry in China.


Progress in the Risk Analysis of Microbial Contamination of Frozen Drinks and Prevention and Control Measures against It

LIU Yuan, CAO Dongli, YAN Jie, FANG Ping, LI Ruiguang

2021, 44(5):  58-62.  DOI: 10.15922/j.cnki.jdst.2021.05.011

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The frozen drink industry has been developing rapidly in recent years. However, while the frozen drink market is expanding, some prominent problems such as microbial contamination have been exposed. Based on the results of recent food safety surveys on frozen drinks, the risk of microbial contamination of frozen drinks is analyzed in this paper, and some measures to prevent control microbial contamination are put forward based on the characteristics of the manufacturing process of frozen drinks. This article is expected to contribute to the improvement of the food safety level of frozen drinks in China.

Progress in Analytical Techniques for Iodine in Milk and Dairy Products

WU Lunwei, LIU Lijun, DUAN Guoxia, TANG Shuo, LIU Chunxia, LI Cuizhi

2021, 44(5):  63-67.  DOI: 10.15922/j.cnki.jdst.2021.05.012

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Iodine is an important index of the nutritional quality of milk. Milk and dairy products are important dietary sources of iodine for humans, which has always aroused extensive concern. With the continuous exploration of nutrients in foods, research on iodine in milk has been increasingly intensified and refined. This paper reviews the recent literature on the factors that affects the iodine content of milk and the analytical methods that have been applied to determine it, which is expected to provide a reference for researchers in this industry and also provide a theoretical basis for the labelling of iodine in infant formula preparation.