Table of Content

01 July 2019, Volume 42 Issue 4

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Basic Research

Antioxidant Properties of Glycosylated Whey Protein with Fucoidin

AI Zhengwen, YU Peng

2019, 42(4):  1-4.  DOI: 10.15922/j.cnki.jdst.2019.04.001

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In this study, whey protein was glycosylated with fucoidin under dry conditions. The change of browning degree was investigated during the glycosylation process, and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and iron reducing power of the reaction products at different reaction times were measured. The results showed that the glycosylation reaction could significantly increase the degree of browning. In addition, compared with whey protein or fucoidin alone, glycosylation significantly increased the DPPH radical scavenging capacity and reducing power of their mixtures at various ratios. The DPPH radical scavenging capacity of their 1:3 mixture reached the maximum (74.28%) at 80 h, a 30% increase compared with that at 0 h. However, it was lower than that of 0.01% VC.

Differences in Mineral Element and Vitamin Contents in Fresh and Fermented Milks from Minor Species of Dairy Animals from Western China

WANG Haiyan, WEN Rong, LIU Dengli, MA Xiaoyi, WANG Huanzi, FAN Shutian, SUN Qiwu, GE Wupeng

2019, 42(4):  5-9.  DOI: 10.15922/j.cnki.jdst.2019.04.002

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The purpose of this study was to investigate the effects of geographical origin, dairy animal species and fermentation on the contents of mineral elements (calcium, iron and zinc), vitamin A and vitamin E in milk from minor dairy species (horse, camel and yak). In total, 86 samples of fresh and fermented milk were collected in main pastoral areas of Xinjiang, Inner Mongolia, Qinghai and Gansu in western China. The contents of mineral elements and vitamins in these samples were determined and by inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC), respectively. The results showed that: 1) There was no significant difference in the contents of calcium, iron and zinc in fresh horse milk between Xinjiang and Inner Mongolia (P > 0.05), whereas there was a significant difference in the contents of calcium and iron in fresh camel milk between the two pastoral areas, as well as in the contents of iron and zinc in fresh yak milk between Gansu and Qinghai (P < 0.05); the contents of vitamins A and E were higher in fresh camel milk from Xinjiang than Inner Mongolia, as well as in fresh yak milk from Qinghai than Gansu (P < 0.05). 2) There were significant differences in calcium, iron and zinc contents among dairy animal species with significantly higher levels for each element being observed in yak milk than in camel milk and horse milk (P < 0.05); likewise, significant inter-species differences in the contents of vitamin A and E in milk were found (P < 0.05); the contents of both vitamins were slightly higher in horse milk from Inner Mongolia than Xinjiang (P > 0.05). 3) Fermentation had no significant effect on mineral element contents in milk. The content of vitamin E in fermented horse milk was significantly higher than in fresh horse milk (P < 0.05), and the contents of vitamins A and E in fresh milk from the other species decreased in varying degrees after fermentation.

Isolation and Identification of Antioxidant Peptide from Culture Supernatant of Biifdobacterium

WANG Shibo, ZHANG Jinlan, LI Pinglan

2019, 42(4):  10-15.  DOI: 10.15922/j.cnki.jdst.2019.04.003

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In this paper, the culture conditions for higher antioxidant activity in the culture supernatant of Bifidobacterium animalis subsp. lactis strain B013 were optimized by response surface methodology. The results showed that an inoculum size (defined by OD600 nm) of 0.66, a culture time of 17.84 h and a glucose concentration of 3.04% were determined as the optimal conditions. Treatment with different enzymes and at different temperatures conformed that the antioxidant activity of the culture supernatant was due to the presence of bioactive peptides. A total of 8 peptides were separated and purified by solid phase extraction and ultrafiltration, and they were analyzed by liquid chromatography tandem mass spectrometry. One (QYPLGPK) of the peptides was screened for possible antioxidant activity by bioinformatics and computer simulation. It was verified that the total antioxidant capacity of QYPLGPK at a concentration of 10 mg/mL was (0.249 ± 0.011) mmol Trolox/L.

Characterization and Preliminary Isolation of Antimicrobial Substances from Fermentation Broth of Paenibacillus bovis BD3526

HUA Bangqing, WU Zhengjun

2019, 42(4):  16-20.  DOI: 10.15922/j.cnki.jdst.2019.04.004

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Paenibacillus bovis BD3526 was cultured in a medium containing 20 g/L glucose, 20 g/L starch, 20 g/L ammonium sulphate, 10 g/L yeast extract, 2.6 g/L dipotassium hydrogen phosphate, 0.5 g/L MgSO4·7H2O and 0.25 g/L NaCl for 48 hours to produce antimicrobial substances with good thermal stability, acid and alkali resistance. The results of protease treatment showed that the fermentation supernatant contained antimicrobial peptides. It had strong antimicrobial activity against Gram-positive bacteria, but not against Gram-negative bacteria. At least two antibacterial substances were isolated by Sephadex LH-20 gel column chromatography from the fermentation supernatant, but not from wheat bran fermented with Paenibacillus bovis BD3526.

Analysis & Detection

Determination of Lactose in Low-Lactose Milk and Lactose-Free Milk by Ion Chromatography

HU Xue, WU Lunwei, LIU Lijun, LI Cuizhi, Lü Zhiyong, DUAN Guoxia, YUE Hong, CHEN Jing, LIU Chunxia, ZHAO Jing

2019, 42(4):  21-24.  DOI: 10.15922/j.cnki.jdst.2019.04.005

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A method for the determination of lactose in low-lactose milk and lactose-free milk by using ion chromatography was developed. Lactose from samples was extracted with 3% acetic acid as a protein precipitator. The method was performed on a CarboPacTM PA20 column by gradient elution. The analyte was detected with an electrochemical detector and quantified by an external standard method. The limit of quantification was 100 mg/kg and the limit of detection was 50 mg/kg for lactose in milk. The recoveries at spiked concentration levels of 100–500 mg/kg were 92.3%–103.4%, with relative standard deviations between 1.44% and 4.43%. This method proved to be rapid, accurate, repeatable, sensitive and simple.

Determination of Multiple Trace Elements in Dairy Feeds by Inductively Coupled Plasma Emission Spectrometry

NING Yuelian, ZHANG Li, LIU Lijun, LI Cuizhi, HU Wenhui, ZHAO Jing

2019, 42(4):  25-29.  DOI: 10.15922/j.cnki.jdst.2019.04.006

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Inductively coupled plasma emission spectrometry (ICP-OES) was used to determine the contents of 12 trace elements (K, Na, Ca, Mg, Fe, Zn, Cu, Mn, P, Sr, Al, and Cr) in premixed feed and crude feed for dairy cows. Samples were pretreated with microwave digestion before being analyzed. The calibration curves of all elements were linear with correlation coefficients above 0.999 8. The spiked recoveries for this method were 90.0%–106.9%, and the coefficients of variance (CV) for six replicate determinations were 0.69%–8.70%. With the advantages of low limits of detection and high sensitivity and accuracy, this method could be useful for the simultaneous determination of multiple trace elements in dairy feeds.

Detection of Multiple Mycotoxins in Dairy Feeds Using Biochip Technology

WANG Yunxia, ZHAO Shuhuan, HOU Xiaxia, LIU Lijun, LI Cuizhi, Lü Zhiyong

2019, 42(4):  30-33.  DOI: 10.15922/j.cnki.jdst.2019.04.007

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The residues of ochratoxin A, deoxynivalenol, aflatoxins B1 and zearalenone in dairy feeds were simultaneously detected using biochip array technology. The method accuracy, precision and reproducibility were evaluated. The results obtained that the correlation coefficient of the calibration curve for each analyte was greater than 0.99. The recoveries for quality control sample and negative sample at two spiked levels varied from 80% to 120%. The coefficient of variance (CV) was less than 15% for accuracy and reproducibility and was less than 10% for reproducibility. Compared with high performance liquid chromatography, this method gave consistent results with a simpler sample pretreatment procedure. In conclusion, the biochip array method was simple and accurate and it could provide an efficient and reliable tool for mass screening of samples.

Reviews

Progress in Application of Cereals in Dairy Products and Processing of Dairy Products Containing Cereals for Use as Staple Foods

FAN Hongxiu, ZHANG Yanrong, KONG Xiaohan, SU Wenjing

2019, 42(4):  34-39.  DOI: 10.15922/j.cnki.jdst.2019.04.008

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As a representative healthy food, dairy products have always been favored by consumers. The nutritional and health properties of dairy products can be improved by incorporating cereals, not only enhancing the popularity of dairy products for consumption as staple foods and the development of functional dairy products, but also promoting the diversified and healthy development of the dairy processing industry. This article reviews the application of cereals in dairy products with a focus on technical aspects, the stability of dairy products containing cereals, the impact of cereal ingredients and processing conditions on the product quality, structural system and processing properties, and it summarizes the past and present status of research on dairy products containing cereals. This review hopes to provide detailed information to promote the development of dairy products containing cereals and to popularize their consumption as staple foods.

Progress in the Determination of Flavor Quality and Residual Microorganisms in Pasteurized Milk

YANG Shanshan, DING Ruixue, LIU Yumeng, SUN Xueting, YUE Xiqing, WU Junrui

2019, 42(4):  40-45.  DOI: 10.15922/j.cnki.jdst.2019.04.009

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Pasteurized milk is favored by consumers worldwide because of its mild sterilization conditions, which can not only kill most pathogenic bacteria in raw milk but also maintain the main nutrients and flavor of fresh milk to the maximum extent. However, because low-temperature sterilization cannot completely inactivate all microorganisms in raw milk, some microorganisms remain in the final product and cause spoilage, which restricts the production, sale and consumption of pasteurized milk. The traditional method of detecting dairy quality is simple and rough. Therefore, this paper reviews the recent progress in the determination of the nutritional and microbial quality of pasteurized milk and other dairy products, in order to provide a theoretical basis for improving product quality and optimizing processing conditions.

Recent Progress in Understanding the Role and Mechanism of Action of Probiotics in Prevention and Treatment of Immune, Metabolic and Neuroemotional Disorders

XU Yu

2019, 42(4):  46-50.  DOI: 10.15922/j.cnki.jdst.2019.04.010

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While research on the functional effects of probiotics has been extended to include their roles in prevention and treatment of immune, metabolic and neuroemotional disorders, a systematic review of the numerous studies in this regard is still lacking in the literature. In this paper, we summarize recent animal and clinical studies on the two probiotics, Lactobacillus and Bifidobacterium and recent studies on their mechanism of action. A number of studies demonstrate that the application of probiotics as a functional food ingredient will help further improve people’s health and living standard. The mechanism of action of probiotics on human diseases and disorders especially the body’s responses to different probiotics, which allows the development of therapeutic strains for clinical applications, will represent an important direction of research in the future.