Table of Content

01 November 2019, Volume 42 Issue 6

Previous Issue    Next Issue

Basic Research

Analysis of Nutritional Composition and Whey Protein Composition of Sheep Milk: A Comparison withMilk from Humans and Other Mammals

WU Yifan, GE Wupeng, LIU Kairu, SONG Yuxuan, ZHAO Lili, ZHANG Wenbo, WANG Yuxin, LIANG Xiuzhen

2019, 42(6):  1-5.  DOI: 10.15922/j.cnki.jdst.2019.06.001

Asbtract ( )   HTML ( )   PDF (1386KB) ( )  

Related Articles | Metrics

The purpose of this study was to explore the differences in nutritional components and whey protein components between sheep milk and milk from humans and other animal species used for dairy production. The whey protein components of milk from Hu sheep, East Friensian Milk sheep and their F1 hybrid at different stages of lactation were analyzed and compared with those of goat, cow and human milk. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Native-PAGE were used to identify landmark proteins that differed between milk samples. The contents of milk macronutrients like protein, fat and lactose significantly varied between sheep breeds, between lactation stages, and between sheep and other animal species (P < 0.05) and they showed a certain trend. SDS-PAGE showed that β-lactoglobulin and lactoferrin differed between sheep and human milk, α-lactalbumin differed between sheep and goat milk, and immunoglobulin G (IgG) heavy chain differed between sheep and cow milk. Native-PAGE indicated that there was one protein band that differed between sheep and goat whey as well as three ones that differed between sheep milk and human and cow whey.

Processing Technology

Process Optimization for the Development of Dairy Beverage Supplemented with Tremella funciformis and Five Grains and Evaluation of Its Rheological Properties during Storage

ZOU Yan, FAN Hongxiu, GAO Nina, ZHANG Yanrong

2019, 42(6):  6-12.  DOI: 10.15922/j.cnki.jdst.2019.06.002

Asbtract ( )   HTML ( )   PDF (2098KB) ( )  

Related Articles | Metrics

This study investigated the optimization of formulations for dairy beverage supplemented with an extruded mixture of Tremella funciformis and five grains using one-factor-at-a-time and orthogonal array design methods. The sensory evaluation score and stability of the beverage were evaluated as a function of the amount of the extruded product, sieve mesh size used on the powdered extrudate and the amount of the composite stabilizer. Changes in the rheological properties and particle size distribution of the beverage during 7 days of storage at 4, 25 and 37 ℃ were measured by a rheometer and a particle size analyzer, respectively. The optimum process conditions were determined as follows: adding extrudate at 5% and the composite stabilizer at 0.4% and sieving the extrudate through a 160-mesh sieve. The sensory evaluation score and stability of the beverage produced under the optimized conditions were (90.14 ± 0.32) points and (92.27 ± 0.07)%, respectively. After storage at 4, 25 and 37 ℃, the beverage was characterized as a pseudoplastic fluid in static rheology and as a weak gel in dynamic rheology. After storage at 4 ℃, the viscosity coefficient and particle size distribution were similar to those before storage. To maintain its taste and shelf life (up to 180 days), the beverage should be stored at 4 ℃, and cold chain distribution is recommended for it.

Optimization of Submerged Culture Conditions for Spore Production by Monascus purpureus M-4

TENG Junwei, ZHOU Zhihan, LIU Zhenmin, SU Miya, ZHENG Yuanrong, LIU Jing, JIAO Jingkai

2019, 42(6):  13-20.  DOI: 10.15922/j.cnki.jdst.2019.06.003

Asbtract ( )   HTML ( )   PDF (2574KB) ( )  

Related Articles | Metrics

The optimization of medium components and culture conditions for improved spore production of Monascus purpureus M-4 in submerge culture was performed using a combination of one-factor-at-a-time (OFAT) method and response surface methodology (RSM). The OFAT results showed that potato extract powder and glucose were the optimal nitrogen and carbon source, respectively and that their optimal concentrations were 0.4 and 2.0 g/100 mL, respectively. The optimal culture conditions that provided the maximum number of spores were as follows: initial medium pH 6.72 (natural pH), medium volume in a 500-mL triangular flask 120 mL, concentration of added CaCO3 2.0 g/100 mL, number of passages 2, and culture time 72 h. Potato extract powder and glucose concentration as well as culture time were identified as main variables that influence spore production and their optimal levels were determined to be respectively 0.38 g/100 mL, 2.2 g/100 mL and 6.5 d using RSM. The highest spore number of (7.47 ± 0.15) × 106 CFU/mL was experimentally obtained under the optimized conditions, which was close to the predicted value (7.53 ± 0.31) × 106 CFU/mL. The average error between the predicted and experimental values was 0.79%. A 31.13-fold increase in spore number was achieved by the optimization. Besides, the spore-producing ability per unit volume of strain M-4 was greatly improved.

Effect of Reconstitution Temperature on Survival Rate of Probiotics in Infant Formula

JIA Hongxin, JIE Liang, LUO Ni

2019, 42(6):  21-24.  DOI: 10.15922/j.cnki.jdst.2019.06.004

Asbtract ( )   HTML ( )   PDF (1071KB) ( )  

Related Articles | Metrics

Infant formula (IF) containing probiotics was reconstituted at different temperatures (40, 50, 60 and 70 ℃) in order to analyze the effects of reconstitution temperature and methods (direct reconstitution in warm water and sequential reconstitution in warm and cool water) on the survival rate of probiotics. At the same time, microbial change in reconstituted IF were measured during storage at 5 ℃ for up to 24 h. The results showed that as the reconstitution increased, the survival rate of probiotics decreased. At the same reconstitution temperature, the second reconstitution method resulted in a significantly higher survival rate than did the first one. Reconstitution temperatures of 40 and 50 ℃ were beneficial to the survival of probiotics (survival rate > 60%). Storage at 5 ℃ ensured effectively the survival of the probiotics in reconstituted IF while controlling the growth of other microorganisms. In conclusion, IF containing probiotics is recommended to be reconstituted at 40–50 ℃ so as to ensure the survival of probiotics in the reconstituted IF.

Analysis & Detection

Effect of Milk Fat on the Flavor of Fermented Milk

LUO Tianqi, CAI Miao, WANG Shijie, ZHU Hong, YANG Zhennai

2019, 42(6):  25-29.  DOI: 10.15922/j.cnki.jdst.2019.06.005

Asbtract ( )   HTML ( )   PDF (1394KB) ( )  

Related Articles | Metrics

Fermented milks were prepared using raw milk with different fat contents, and their flavor was evaluated. The pH trend during fermentation indicated that the change in milk fat content had no effect on the acid production of lactic acid bacteria. Rheological and texture measurements showed that with the increase in milk fat content, the elastic modulus and the viscous modulus decreased, hardness and cohesiveness did not obviously change, but gumminess significantly increased (P < 0.05). By gas chromatography-mass spectrometry (GC-MS), a total of 34 flavor substances were detected from 5 groups of fermented milk samples, including 7 hydrophilic ones and 27 lipophilic ones. Change in milk fat content greatly affected the content of flavor substanc es. Principal component analysis and correlation analysis showed that change in milk fat content caused significant differences in flavor between fermented milk samples, and the trend of flavor contents was related to their hydrophobicity. With the increase in milk fat content, the content of milk fat degradation products such as 2-nonanone and hexanal but not γ-butyrolactone increased first and then decreased. Among other substances, the content of hydrophilic flavor compounds increased first and then decreased, and the content of lipophilic compounds decreased continuously.

Determination of Vitamin K2 (Menaquinone-7) in Milk Powder by High Performance Liquid Chromatography

WANG Yao, ZHANG Min, MA Xiaochong, LIU Xing, CHAI Yanbing, ZHANG Yaoguang, LI Fei, LI Xingjia

2019, 42(6):  30-33.  DOI: 10.15922/j.cnki.jdst.2019.06.006

Asbtract ( )   HTML ( )   PDF (1764KB) ( )  

Related Articles | Metrics

This paper describes a method for determination of vitamin K2 (menaquinone-7, MK-7) in milk powder using high performance liquid chromatography (HPLC). The sample was hydrolyzed with lipase (250 mg/g) for 2 h, saponified with potassium carbonate (500 mg/g), extracted with n-hexane, concentrated by rotary evaporation, reconstituted with methanol/isopropanol (4:1), and post-derivatized with C18 column and reduced column before being analyzed by HPLC with a fluorescence detector. The analyte was quantified by external standard method. The results showed that the peak of MK-7 appeared at about 19.47 min, and the calibration curve for it showed a good linear relationship in the range of 0.0–1.5 μg/mL (R2 = 0.999 95). The recoveries for blank samples spiked at 5, 10 and 25 μg/100 g were between 87.9% and 94.3%, with relative standard deviations of 0.9%–6.4%. When 2 g of sample was taken and the volume was made up to 1 mL, the detection limit was 0.15 μg/100 g and the quantification limit was 0.5 μg/100 g. The method was simple with high accuracy, sensitivity and stability, and could be used for the detection of vitamin K2 (MK-7) content in milk powder.

Reviews

A Review of the Effect of High Hydrostatic Pressure on Proteins and Enzymes in Dairy Products

CHENG Kaili, HU Zhihe, ZHAO Xufei, JIA Lingyun, XIAO Houdong, DING Xinyu

2019, 42(6):  34-40.  DOI: 10.15922/j.cnki.jdst.2019.06.007

Asbtract ( )   HTML ( )   PDF (1591KB) ( )  

Related Articles | Metrics

High hydrostatic pressure (HHP) is considered one of the most sustainable and green technologies. HHP can prolong the shelf life of food, change the physical and chemical properties of milk proteins and enzymes, and improve the functions, nutritional characteristics and sensory quality of food. In this paper, the structural and functional changes of proteins and enzymes in milk caused by HHP treatment are reviewed, which provides a rationale for the application of high hydrostatic pressure in dairy products.

A Review of Technologies for Rapid Detection and Control of Psychrophilic Bacteria in Raw Milk

HONG Qing, LI Nan, LIU Zhenmin

2019, 42(6):  41-45.  DOI: 10.15922/j.cnki.jdst.2019.06.008

Asbtract ( )   HTML ( )   PDF (977KB) ( )  

Related Articles | Metrics

Psychrotrophic bacteria grow and reproduce rapidly in raw milk under cold conditions while producing some proteases and lipases which may affect the quality of both raw and processed milk. On the basis of the data on raw milk under different regional, seasonal and management conditions collected in China and abroad, this article presents a comparative analysis of the composition and quantity of psychrotrophic bacteria and of the prospects for the application of various technologies for rapid detection of psychrotrophic bacteria in raw milk with focus on the detection time, the limit of detection and the correlation coefficient of the calibration curve as well as the advantages and disadvantages. Next, it summarizes the current status of the control of psychrotrophic bacteria in practice. We believe that the quality and safety control of dairy products will be guaranteed by the combined use of rapid detection technologies and microbial traceability technologies.

Recent Progress in the Application of Chromatography and Mass Spectrometry for theDetection of Carbohydrates in Milk Powder

LI Li, XUE Weifeng, CAO Wenjun

2019, 42(6):  46-50.  DOI: 10.15922/j.cnki.jdst.2019.06.009

Asbtract ( )   HTML ( )   PDF (924KB) ( )  

Related Articles | Metrics

This paper reviews the progress in the application of gas and liquid chromatographies, ion chromatography and liquid chromatography-mass spectrometry for the detection of carbohydrates in milk powder. It points out the advantages and disadvantages of these methods. While ion chromatography is nowadays the most used technique to detect carbohydrates in milk powder, ion chromatography will be an important trend in this field owing to its distinct advantages in terms of sensitivity and anti-interference ability.

Recent Advances in the Detection of Pyrethroid Pesticide Residues in Milk Products

LIANG Jianying, HU Xue, XIE Ruilong, LIU Lijun, LI Cuizhi, ZHANG Zhiwei

2019, 42(6):  51-55.  DOI: 10.15922/j.cnki.jdst.2019.06.010

Asbtract ( )   HTML ( )   PDF (1544KB) ( )  

Related Articles | Metrics

This paper summarizes and compares the maximum residue limits for pyrethroid pesticides in milk products in China and several other countries. At the same time, the main factors affecting the accuracy of the determination of pyrethroid pesticide residues in dairy products, including calibration curve fitting and experimental repeatability, are determined through calculation of the measurement uncertainty. Furthermore, it can be argued that the most fundamental influencing factor is the sample pretreatment method.