Table of Content

01 May 2020, Volume 43 Issue 3

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Processing Technology

Optimization of Fermentation Conditions for Exopolysaccharide Production by Lactobacillus plantarum XN1904E

CHEN Qi, LEI Wenping, XIAO Qian, YAO Hui, LUO Jie, LIU Chengguo, ZHOU Hui

2020, 43(3):  1-5.  DOI: 10.15922/j.cnki.jdst.2020.03.001

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The optimization of culture temperature, initial medium pH, and carbon and nitrogen sources for improved production of extracellular polysaccharides by Lactobacillus plantarum XN1904E was carried out using one-factor-at-a-time (OFAT) and orthogonal array design methods. The results showed that the optimal culture conditions were determined as follows: initial pH 6.5, temperature 37 ℃, galactose as the best carbon source, and fish peptone as the best nitrogen source. Under these conditions, the production of extracellular polysaccharide was 235.41 mg/L. The polysaccharide at 0.2 mg/mL had antioxidant activity in terms of scavenging rate (27.54%) against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical.

Response Surface Methodology for Optimizing the Formulation of Cryoprotectants for Bifidobacterium lactis Z-1

XU Xianrui, LI Cuifeng, SUI Yongjun, ZHANG Zongbo, YANG Honglai, LI Daohe, CHEN Zhengyan, ZHANG Lanwei

2020, 43(3):  6-11.  DOI: 10.15922/j.cnki.jdst.2020.03.002

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This study describes the optimization of the formulation of cryoprotectants for Bifidobacterium lactis Z-1 using response surface methodology (RSM). Using the Plackett-Burman design, trehalose, sucrose, L-cysteine hydrochloride concentration were identified as factors with a significant influence on the viable count of lyophilized Bifidobacterium lactis Z-1. Subsequently, the optimal response ranges of the three factors were determined using the steepest ascent method. The levels of these factors were further optimized using RSM with Box-Benhnken design. As a result, a regression model was fitted into the experimental data. The optimal levels of trehalose, sucrose and L-cysteine hydrochloride were determined as 200.51, 46.16 and 2.31 g/L, respectively, while the other ingredients were the same as those in the traditional recipe (skimmed milk powder 100 g/L, whey protein powder 20 g/L, glycerol 4 g/L, sodium isoascorbate 10 g/L and sodium glutamate 8 g/L).

Analysis & Detection

Establishment of a Helicase-Dependent Isothermal DNA Amplification Method for Rapid Detection of Gluconobacter in Fermented Milk

LIU Dong, ZHANG Jie, ZHU Huadong, ZHOU Wei, ZHANG Yan

2020, 43(3):  12-16.  DOI: 10.15922/j.cnki.jdst.2020.03.003

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A rapid method using helicase-dependent isothermal DNA amplification (HDA) for the detection of Gluconobacter in fermented milk was established. The ITS gene sequence (gene number KF896260.1) of Gluconobacter was selected as the target gene for design of specific primers, and the concentrations of UvrD helicase and T4 gp32 in the reaction system were optimized to establish an optimal reaction system. The HDA method was used to directly detect Gluconobacter in fermented milk. The established HDA system was used to amplify and electrophoretically detect various strains in fermented milk to verify the specificity of the method and determine its detection limit. The results showed that the detection of Gluconobacter in fermented milk by the HDA method was consistent with the designed sequence length (309 bp) and the detection limit was 4.3 × 101 CFU/g. The appropriate amounts of UvrD helicase and T4 gp32 added in the reaction system were 0.1 and 5.0 μg, respectively. The method is highly sensitive and time saving.

Quantitative Determination of 21 β-Agonists in Milk by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

ZHANG Lijia, HU Xue, MO Nan, BAI Yanmei, ZHANG Yue, LIU Lijun, LI Cuizhi

2020, 43(3):  17-22.  DOI: 10.15922/j.cnki.jdst.2020.03.004

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An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantitative determination of 21 β-agonists in milk. The samples were hydrolyzed and cleaned up a solid-phase extraction column. The analytes were separated by UPLC with an Acquity UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm) using a gradient mobile phase consisting of 0.1% formic acid aqueous solution and methanol (10 : 90, V/V). Identification and quantification were achieved by UPLC-MS/MS with multiple reaction monitoring (MRM) under the positive ion mode The limit of quantitation of all β-agonists was 0.05 μg/kg. The average recovery varied from 61.0% to 124.3% at spiked concentration levels of 0.05, 0.10 and 0.50 μg/kg with relative standard deviations (RSDs) of 2.39%–10.66%. Our results demonstrate that the method is stable, accurate and sensitive, and can be used for the determination of the 21 β-agonists residues in milk.

Establishment of a Microbiological Method for Detection of Lactobacillus fermentum CECT5716 in Milk Powder

WANG Yunxia, HOU Xiaxia, ZHAO Shuhuan, JING Lijuan, LIU Lijun, LI Cuizhi

2020, 43(3):  23-26.  DOI: 10.15922/j.cnki.jdst.2020.03.005

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In recent years, the addition of probiotics to milk powder has gradually become a research focus. In order to ensure the product quality and safety, a microbiological detection method for Lactobacillus fermentum CECT5716 in milk powder has been established. It was found that the population of Lactobacillus fermentum in milk powder could be accurately counted by spreading serial 10-fold dilutions in buffered peptone water (BPW) onto MRS plates and culturing them under anaerobic conditions at (36 ± 1) ℃ for (48 ± 2) h, with clear discrimination from inoculated bifidobacteria. This method was more suitable for counting Lactobacillus fermentum than the Chinese national standard method (GB 4789.35?2016), and had the advantages of high discrimination capacity, short culture time, simple operation, good repeatability, and high accuracy. This method also included 16S rDNA sequence analysis of the strain for its subsequent molecular identification. There was no significant difference in the accuracy of this method versus the national standard method in detecting 20 samples prepared in our laboratory (P = 0.127).

Determination of Lead in Milk Powder by Inductively Coupled Plasma Mass Spectrometry: Optimization of Experimental Conditions for Reduced Detection Limit

ZHAO Jing, NING Yuelian, XIE Ruilong, Lü Zhiyong, LI Cuizhi, LIU Lijun

2020, 43(3):  27-30.  DOI: 10.15922/j.cnki.jdst.2020.03.006

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By analyzing some factors involved in the determination of lead in milk powder by inductively coupled plasma mass spectrometry (ICP-MS) such as containers and reagents used, an ultrasonic cleaning method was established to effectively reduce the blank value. The method gave a detection limit of 0.005 mg/kg, which was much lower than that (0.02 mg/kg) of traditional methods. The recoveries of samples spiked at concentration levels of 0.005–0.015 mg/kg ranged from 86.9% to 119.0% with relative standard deviations (RSDs) of 3.1%–12.3%, meeting the requirements for methodological validation. Hence, the method proved to be overall feasible and suitable for the detection of lead in milk powder with reduced detection limit.

Reviews

Probiotics and Development of Functional Yogurt: A Review of Recent Progress

LI Nan, LIU Zhenmin

2020, 43(3):  31-38.  DOI: 10.15922/j.cnki.jdst.2020.03.007

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In the past ten years, with the development of advanced scientific technologies and continuous research efforts, great progress has been made in the understanding of probiotics. Especially, how probiotics promote human health is becoming increasingly clear, and probiotic preparation and industrialization technologies are become increasingly mature, which provides a solid foundation for the development of new types of fermented milk. This review focuses on recent progress in understanding the functions, mechanisms of action, genetic transformation and metabolic regulation of probiotics. The probiotic properties, genomic characteristics and extracellular polysaccharide-producing ability of Lactobacillus casei LC2W isolated from Inner Mongolian kumiss and Lactobacillus plantarum ST-Ⅲ isolated from pickles are specifically discussed. Fermented milk containing pure Lactobacillus plantarum can be developed based on Lactobacillus plantarum enrichment, which is expected to provide a theoretical basis for the development of protiotics and functional fermented milk. Fermented dairy products are good carriers for probiotics. Researchers must absorb modern scientific and technological achievements regarding probiotics, step up evidence-based medical demonstration and obtain more clinical research data based on bioactive molecules and biological activity evaluation of probiotics, so that the novel types of fermented dairy products can make more contributions to human health.

Comparative Analysis of Domestic and Foreign Standard for the Use of Nutritional Fortifiers in Food for Special Medical Purposes

ZHANG Lantian, WANG Chenyuan, ZHANG Bin, WU Lei, ZHANG Yan, SHI Guohua

2020, 43(3):  39-44.  DOI: 10.15922/j.cnki.jdst.2020.03.008

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As a nutritional supplement for people with special needs, the food for special medical purposes (FSMP) has occupied an important position in the global market. As the main source of added nutritional components in FSMP, nutritional fortifiers are of great significance to improve its quality. This paper focuses on the comparative analysis of the standards and regulations of the Codex Alimentarius Commission (CAC), the EU and China on nutrients and nutritional fortifiers in FSMP with respect to limits, ingredients, sources, and so forth, in order to provide useful information for improving the standards for the use of nutritional fortifiers in FSMP in China.

Recent Progress in Infant Formulas Simulating the Fat Composition of Human Milk

JIE Liang, SU Miya, JIA Hongxin, CHEN Wenliang, QI Xiaoyan

2020, 43(3):  45-49.  DOI: 10.15922/j.cnki.jdst.2020.03.009

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The fat composition of human milk is distinct from that of milk from other mammals and vegetable oils. Breast milk is considered the optimal food source for neonates; however it is not always available for the development of infants. Manufacturing infant formulas that simulate the composition and function of breast milk is therefore of great importance to optimize outcomes of formula-fed infants, and infant formulas that simulate the fat composition of human milk have been developed consequently. With the continuous progress in nutritional science, advancements have been made in simulating breast milk at the triglyceride level. This paper reviews recent progress in infant formulas simulating the fat composition of human milk.

Progress in Research on Dairy Flavors

SUN Jiaqing, FENG Tao, SONG Shiqing, YAO Lingyun, SUN Min, WANG Huatian

2020, 43(3):  50-54.  DOI: 10.15922/j.cnki.jdst.2020.03.010

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As increasing attention has been paid to the flavor of dairy products, research on dairy flavors will promote the rapid development of the dairy flavor industry. In this paper, we summarize recent progress in research on dairy flavors, review the main flavor compounds of some common dairy products, analyze the mechanism of off-flavor formation, and provide some solutions to this problem based on the preparation process for dairy flavors. It is expected that this review will provide new ideas for the development of flavored dairy products and dairy flavors in the future.