Table of Content

01 September 2020, Volume 43 Issue 5

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Basic Research

Composition and Digestion Characteristics of Proteins in Donkeys' Milk and Mares' Milk

XU Jinghui, WANG Zhaoxia, ZHANG Fuxin, CAI Junna

2020, 43(5):  1-7.  DOI: 10.15922/j.cnki.jdst.2020.05.001

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The composition and digestion characteristics of proteins in donkeys’ milk and mares’ milk were investigated by sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) analysis. The results showed that the digestibility of casein in donkeys’ milk and mares’ milk was 97.9% and 96.7% respectively after digestion in simulated gastric juice for 120 min, and was 98.6% and 97.7% respectively after digestion in simulated intestinal juice for 30 min. It took 30 min to almost completely digest proteins in both milks in simulated gastrointestinal juice, and mares’ milk proteins were easier to digest than donkeys’ milk proteins. Taken together, it was found that donkeys’ milk and mares’ milk proteins were mainly digested in simulated intestinal juice rather than simulated gastric juice and the latter was more digestible than the former.

Bioactive Substances Inhibited Milk Fat Degradation during Simulated Gastrointestinal Digestion

WANG Jingxuan, AN Yuejia, SHI Xinyang, CAO Ge, LI Xinning, LIANG Xiaona, YANG Mei, CAO Xueyan, YUE Xiqing

2020, 43(5):  8-12.  DOI: 10.15922/j.cnki.jdst.2020.05.002

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In order to explore the inhibitory effect of bioactive substances on the degradation of milk fat during simulated gastrointestinal digestion, the impact of bioactive substances on the in vitro digestibility of milk proteins was examined as well as the inhibitory effect on pancreatic lipase activity and the micellar solubility of cholesterol. The results showed that the in vitro digestibility of milk proteins was inversely proportional to the concentration of the tested bioactive compounds, which decreased from 90.94% to 68.37% and 86.00% with increasing concentration of epigallocatechin (EGC) and β-glucan, respectively. The inhibitory effect of EGC on pancreatic lipase activity decreased to different extents with increased amount of added milk proteins, and so did the inhibitory effect of β-glucan and a mixed solution of 2.5 g/L β-glucan, 3.0 g/L epigallocatechin gallate (EGCG) and 2.0 g/L EGC on the micellar solubility of cholesterol. The inhibitory effect of this mixture on the degradation of milk fat was stronger than that of β-glucan.

Analysis & Detection

Spectrophotometric Determination of Tea Polyphenols in Milk Tea Powder Using Folin-Phenol Reagent

YUE Hong, NING Yuelian, WEN Jing, HUANG Xiaoyan, HU Wenhui, ZHAO Zhen, LIU Lijun, LI Cuizhi

2020, 43(5):  13-16.  DOI: 10.15922/j.cnki.jdst.2020.05.003

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A spectrophotometric method for the determination of tea polyphenols in milk tea powder was developed by using Folin-phenol reagent. Crucial operating parameters such as extraction reagent, number of extraction cycles, temperature and derivatization reagent were investigated. Extraction using 70% methanol solution as the extraction reagent in a hot water bath at 70 ℃ performed twice and oxidization of the resulting extract with Folin-phenol reagent proved optimal. The detection wavelength was selected as 765 nm, and gallic acid was used as the calibration standard for the quantitation of tea polyphenols. The recoveries for whole milk powder spiked at concentration levels of 850–4 500 mg/kg were in the range of 98.9%–104.9%. Good stability and accuracy were achieved. When milk tea powder samples with different contents of tea polyphenols were detected in six replicates, relative standard deviations (RSDs) of 0.29%–0.84% were obtained, indicating good precision. This method proved to be accurate, easy to operate and repeatable with simple and easily available instruments, and thus suitable for the analysis of tea polyphenols in milk tea powder.

Quantitative Analysis of α-Lactalbumin, β-Lactoglobulin and Lactoferrin in Different Dairy Products

ZHANG Min, WANG Yao, SU Yuncong, MA Xiaochong, GHAI Yanbing, ZHANG Yaoguang, LI Fei, LI Xingjia

2020, 43(5):  17-21.  DOI: 10.15922/j.cnki.jdst.2020.05.004

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In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine the contents of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and infant formula. The sample was dissolved with ultrapure water, and reacted with dithiothreitol and iodoacetamide to open disulfide bonds and simultaneously protect sulfhydryl groups before being hydrolyzed with trypsin. After completion of the reaction, aqueous acetonitrile was used for making up to a constant volume, and then centrifugation was carried out to take the supernatant for quantification by external standard method. The results showed that the calibration curves for all analytes were linear in the range of 0–100 μg/mL, with correlation coefficient (r) greater than 0.995. The average recoveries of the analytes from spiked raw milk were 93.5%–117.1%, with relative standard deviation (RSD) ranging from 1.4% to 6.7%. In conclusion, the method was simple, rapid and sensitive, and could be used for the determination of α-lactalbumin, β-lactoglobulin and lactoferrin in milk and milk powder samples.

Determination of Zeaxanthin in Milk Powder by High Performance Liquid Chromatography

HU Xue, DUAN Guoxia, GONG Huili, LIU Chunxia, CHEN Jing, WU Lunwei, LIU Lijun, LI Cuizhi, Lü Zhiyong

2020, 43(5):  22-25.  DOI: 10.15922/j.cnki.jdst.2020.05.005

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A method for the determination of zeaxanthin in milk powder was developed using high performance liquid chromatography (HPLC). The sample was saponified with potassium hydroxide solution to release zeaxanthin, extracted with a mixed solvent of ethyl ether, n-hexane and cyclohexane and frozen for degreasing. The chromatographic separation was performed on a C30 column with gradient elution. The analyte was detected with an ultraviolet detector and quantified by an external standard method. The limit of quantification was 100 μg/100 g and the limit of detection was 30 μg/100 g for zeaxanthin in milk powder. The method recoveries at spiked concentration levels of 90–811 μg/100 g were 85.8%–102.2%, with relative standard deviations ranging from 1.43% to 2.76%. This method was accurate, repeatable, precise and sensitive.

Reviews

Recent Advances in Bio-Production of the Human Milk Oligosaccharide 2'-Fucosyllactose (2'-FL)

XU Zheng, LI Na, ZHU Wanying, ZHANG Wenrui, CHEN Yingli, LUO Zhengshan

2020, 43(5):  26-30.  DOI: 10.15922/j.cnki.jdst.2020.05.006

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Human milk oligosaccharides (HMO) are important bioactive ingredients of breast milk, the most abundant being 2’-fucosyllactose (2’-FL), which is significantly beneficial to the growth and development of infants, and is considered as a novel nutrient supplement with great potential. Recently, great progress has been made in the bio-production of 2’-FL, whose output has reached industrial levels of production. Many multi-national companies have investigated 2’-FL bio-production techniques for a long time. However, universities and companies in China have just begun research in this field, highlighting its great significance. This paper reviews the 2’-FL bio-production pathways and summarizes several recent novel 2’-FL biosynthesis methods.

Human Milk Oligosaccharides: Past Achievements and Current Trends

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

2020, 43(5):  31-36.  DOI: 10.15922/j.cnki.jdst.2020.05.007

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With increasing knowledge about the distribution and beneficial bioactivities of human milk oligosaccharides (HMOs), especially prebiotic activities that modulate the human gut microbiota, HMOs have received growing research attention. However, the application of HMOs is generally difficult. The challenges are the special selection of suitable HMOs for infant formula and the limited amount of HMOs from natural sources. In the literature, there are few studies on the content of special HMOs and their impact on infant health outcomes. In this article, the current status of research on the complex composition, possible sources, functions and safety of HMOs are summarized with focus on the state-of-the-art in these regards. Finally, an outlook on future research directions is given.

A Review of Recent Studies on Milk Fat Globule Membrane: Composition and Separation Techniques

CAO Wenhui, GAO Zengli, WU Yun, LI Hongliang, MU Zhishen

2020, 43(5):  37-42.  DOI: 10.15922/j.cnki.jdst.2020.05.008

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Milk fat is dispersed in milk in the form of fat globules and is surrounded by a three-layer membrane, called milk fat globules membrane (MFGM). MFGM has been extensively studied due to its reported biological functions and emulsification potential. This paper reviews the structure and composition of MFGM, summarizes the existing techniques used for MFGM separation and discusses the effects of different separation process parameters on the composition of MFGM.

A Review on Recent Advances in Application of Aptamers in the Detection of Milk and Dairy Products

ZHANG Yali, NIU Lisha, ZHAO Limin, FAN Sufang, HUANG Yunxia, ZHANG Yan, FAN Bin

2020, 43(5):  43-48.  DOI: 10.15922/j.cnki.jdst.2020.05.009

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Aptamer technology is a new detection technology which has been widely used in the field of animal-origin food safety detection because of its specificity, high affinity, rapidity and low cost. In this paper, we describe the principle and classification of aptamer screening technologies, and we review recent progress in their applications in the detection of food additives, veterinary drug, hormone and antibiotic residues, mycotoxins, and pathogenic bacteria in milk and dairy products.

Current Situation and Analysis of Regulations on Plant-Based Yoghurt

HUA Bangqing, ZHANG Fenghua, SU Yonghong

2020, 43(5):  49-52.  DOI: 10.15922/j.cnki.jdst.2020.05.010

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In recent years, plant-based yogurt has gradually entered the consumer market, and has attracted the eyeballs of consumers with health concepts such as lactose-free and low-cholesterol. At present, the US, the EU and China all regulate plant yogurt as beverages. The U.S. Food and Drug Administration has planned to formulate and release industry guidelines for plant-based milk and yoghurt, while EU regulations prohibit the use of the concept of plant-based yoghurt. In China, this concept has not been written into relevant national standards or industry standards. However, as a new product, plant-based yogurt has the advantages of plants themselves, and its nutritional value can be improved after fermentation. Therefore, relevant standards and regulations should be formulated as soon as possible to regulate the market. In this paper, by comparing the relevant regulations and standards of the US, the EU and China and in view of the particularity of plant-based yogurt, some suggestions on the management of regulations on plant-based yogurt are proposed.