Table of Content

01 March 2022, Volume 45 Issue 2

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Basic Research

Effect of Bacillus licheniformis D3.11 Milk-Clotting Enzyme on Texture Properties of Cheddar Cheese

ZHANG Zhongming, CAO Yingying, WANG Ying, QIAO Haijun, ZHANG Weibing

2022, 45(2):  1-7.  DOI: 10.7506/rykxyjs1671-5187-20220117-006

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This study was conducted to reveal the effect of milk-clotting enzyme (MCE) produced by Bacillus licheniformis on the texture of Cheddar cheese during ripening. Cheddar cheese and Cheddar cheese analogue were prepared with the MCE and designated as CDF and CD3, respectively, and commercial chymosin was used as a control (CCF).The changes in the texture, rheology and microstructure of cheese during ripening were analyzed. The results were as follows: The hardness of the three cheeses increased with maturation time, while the elasticity and chewiness presented a downward trend. The hardness, springiness and chewiness of CDF were the lowest. The scanning electron microscope (SEM) results showed that the compactness of the protein structure decreased with increasing maturity, and the structure of CDF was looser than that of CCF. The rheological results showed that the storage modulus and loss modulus decreased with increasing ripening time up to six months and increasing sweep temperature. The tan δ value decreased during the ripening process, indicating that the fluidity of cheese decreased with increasing ripening time. The fluidity and fusibility of CDF were better than those of the other groups. The above results indicated that the mechanical properties of cheese made with Bacillus licheniformis MCE were better than those made with commercial rennet, while the latter had harder texture and denser protein network structure.

Analysis & Detection

Determination of Six Pesticide Residues in Milk by QuEChERS-Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry

ZHANG Xiaomin, MENG Genhua, LIN Tingjuan, CHEN Xiumei, CHEN Xirong

2022, 45(2):  8-12.  DOI: 10.7506/rykxyjs1671-5187-20211129-005

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In this study, we aimed to establish a method for the determination of six pesticide residues in milk by quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction combined with ultra high performance liquid chromatography-tandem mass spectrometry. Milk samples were extracted with acetonitrile, purified by the QuEChERS approach, and the extract was then blown down to dryness using a stream of nitrogen gas and re-dissolved. The liquid chromatographic separation was achieved by gradient elution using a mobile phase consisting of acetonitrile and 0.1% formic acid in water. The analysis was carried out using positive ion electrospray ionization under the multiple reaction monitoring mode. The external standard method was used for quantification. Excellent linearities were achieved for all target analytes in the range of 1.0–40.0 μg/L with correlation coefficients greater than 0.995. The limit of detection was 0.1 μg/kg, and the limit of quantification was 1.0 μg/kg. The average recoveries of the six pesticide residues from blank milk samples at three spiked concentration levels of 1.0, 2.5 and 5.0 μg/kg ranged from 76.5% to 113.7% with relative standard deviations (RSDs) of 1.5%–6.1%. The proposed method was simple, accurate, efficient and suitable for the rapid screening and quantitative analysis of pesticide residues in milk.

Influence of Pretreatment Process on Accuracy of Determination of Multiple Elements in Milk Powder by Inductively Coupled Plasma-Mass Spectrometry

HUANG Xiaoyan, NING Yuelian, LIU Lijun, YUE Hong, LI Cuizhi

2022, 45(2):  13-17.  DOI: 10.7506/rykxyjs1671-5187-20211129-004

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Sample pretreatment is a key step in element testing, which directly affects the precision and accuracy of analytical results. In order to meet the requirements for the detection of various elements, in this study, we used microwave digestion combined with inductively coupled plasma-mass spectrometry (ICP-MS) operated in the collision reaction mode to determine the content of multiple elements in milk powder, and investigated the influence of sample pretreatment conditions (acid removal time, sample size, and the amount of residual acid) on the detection results. Compared to removing acid mist only, better results were obtained under the following conditions: acid removal temperature was 160 ℃, acid removal time was 97.5 min, and sample size was 0.250 0 g, and the amount of residual acid was 1.0 mL. This pretreatment process is characterized by good stability, high precision and high accuracy.

Determination of Protein Content in Ultra High Temperature Milk by Liquid Chromatography

LAN Li, ZHANG Caixia, GAO Wandong, YU Zhibao, XU Hong, TANG Zhenxin, FAN Min, YANG Mingyang, TIAN Jiamei, ZHANG Xuejiao, ZHANG Jing, HE Xiaoming, GUO Sufang

2022, 45(2):  18-23.  DOI: 10.7506/rykxyjs1671-5187-20211206-008

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A liquid chromatographic (LC) method was established for the determination of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in ultra high temperature (UHT) milk. The proteins in milk were denatured by adding a buffer solution containing bis[tris(hydroxymethyl)aminomethane (BisTris), guanidine hydrochloride, sodium citrate, dithiothreitol, etc. The analytes were detected by an ultraviolet (UV) detector and quantified by the external standard method. The results showed that the calibration curve of each protein had good linearity with a correlation coefficient above 0.995. The recoveries of spiked samples were between 95.2% and 105.0%, the detection limit was 0.01–0.02 g/100 mL, and the relative standard deviation was 0.78%–2.70%. The method is characterized by good separation effect, good repeatability and simple operation, and is suitable for quantitative analysis of α-casein, β-casein, κ-casein, α-lactalbumin and β-lactoglobulin in UHT milk.

Reviews

Progress in Understanding the Composition and Function of Milk Polar Lipids

LI Mohan, SONG Wanying, ZHANG Xiumin, CHEN Jiali, Rehanguli·Abdlla, LIU Aicheng, YU Haikun, ZHANG Juan, CAO Xueyan, YUE Xiqing

2022, 45(2):  24-29.  DOI: 10.7506/rykxyjs1671-5187-20211209-010

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Bovine milk contains 2%–5% lipids, secreted by breast epithelial cells and dispersed in the milk in the form of milk fat globules. Most of the milk fat (about 98%) exists in the milk fat globules in the form of glycerolipids, and the rest (about 2%) is polar lipids, including glycerophospholipids, sphingolipids, glycolipids, mainly distributed in the milk fat globule membrane surface. Despite their relative scarcity, milk polar lipids play an indispensable role in the growth and development of mammals. This review introduces readers to the types of polar lipids in milk, and compares the types and quantities of milk polar lipids from different milk sources including cows, buffalo, yak, sheep, goats, donkeys, camels, and humans. Next, this review summarizes the physiological functions of milk polar lipids including inhibition of neutral fat absorption, regulation of intestinal microbial community composition, prevention of cardiovascular disease, prevention of non-alcoholic fatty liver, promotion of cognitive function and nervous system development, and anti-inflammatory effects with a view to providing reference for the research and development of functional milk fat products.

Recent Progress in the Renal Health Protective Effect and Mechanism of Probiotics Used in Food

XU Yu

2022, 45(2):  30-34.  DOI: 10.7506/rykxyjs1671-5187-20210710-046

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Renal health problems have become major public health issues but are easily overlooked. Existing studies demonstrate that probiotic regulation of the intestinal flora is a new intervention pathway to protect renal health. Nevertheless, little research attention has been paid to the role of probiotics in protecting kidney health. In this paper, we review the protective effects and action mechanisms of probiotics used in food on renal health problems such as chronic nephritis, hemodialysis, hyperuricemia, and hyperoxaluria. We hope that this review can provide theoretical support for the exploitation of new probiotics and the targeted development of probiotic products.

Progress in Knowledge of Human Milk Phospholipids and Development of Infant Formula Powder

JIA Hongxin, SU Miya, CHEN Wenliang, JIE Liang, LIU Haian

2022, 45(2):  35-41.  DOI: 10.7506/rykxyjs1671-5187-20211206-007

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Human milk is the most perfect source of nutrition for infants. It contains all the nutrients needed for the growth and development of infants. Phospholipids can promote the intestinal, brain and cognitive development of infants, which is very important for the healthy development of infants. This paper introduces its readers to the phospholipids in human milk, focusing on the differences in the composition and content of phospholipids in human milk in different countries/regions, as well as the differences in the composition of phospholipids and phospholipid fatty acids in human, bovine, caprine and ovine milk. This review hopefully will provide a basis for the development of infant formula, especially the fine simulation of phospholipid composition and phospholipid fatty acid composition in human milk.

Recent Progress in Understanding the Effects of Ultra-High Pressure Homogenization on Microorganisms and Enzymes in Milk

AI Zhengwen

2022, 45(2):  42-46.  DOI: 10.7506/rykxyjs1671-5187-20211023-059

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Ultra-high pressure homogenization is a newly emerging processing technology. Compared with traditional thermal processing and static high pressure processing, dynamic ultra-high pressure processing has several advantages such as continuity, economy and lower thermal load. With increasing pressure, the effects of shear, turbulence and cavitation caused by high pressure homogenization increases sharply. The temperature of products increases instantaneously during ultra-high pressure processing, which provides a new way for sterilization and enzymatic inactivation in milk. This review article summarizes the application of ultra-high pressure homogenization for sterilization and enzymatic inactivation in milk. Existing studies have shown that ultra-high pressure homogenization can sterilize all microorganisms except Bacillus, and this effect is related to inlet temperature and pressure. Furthermore, temperature has a greater effect on enzymatic inactivation than pressure.

Recent Progress in Postbiotics and Their Applications in Dairy Products

ZHAO Xuanying, YANG Yang, WANG Guojiao, YONG Jingyi, LI Nan

2022, 45(2):  47-54.  DOI: 10.7506/rykxyjs1671-5187-20211109-023

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Postbiotics are a new means of intervention in the intestinal ecosystem that has emerged in recent years. Postbiotics refer to soluble factors (products or metabolic by-products) secreted by living bacteria or released after bacterial lysis, namely small molecules that regulate the health of the host, such as enzymes, peptides, teichoic acid, peptides derived from peptidoglycan, polysaccharides, cell surface proteins, and organic acids. Although the International Symposium of the International Scientific Association for Probiotics and Prebiotics has not yet published a consensus on postbiotics, this concept closely related to probiotics still attracts people’s attention. This paper briefly clarifies the classification and preparation methods of postbiotics, and discusses the advantages and potential application of postbiotics as functional ingredients in dairy products.

Recent Progress in Understanding the Effect of Sialic Acid on Infant Health

JIE Liang, SU Miya

2022, 45(2):  55-59.  DOI: 10.7506/rykxyjs1671-5187-20210813-051

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The rapid growth of infant brains places an exceptionally high demand on the supply of nutrients from the diet, particularly for preterm infants. Sialic acid is an essential component of brain gangliosides and the poly sialic acid chains that modify neural cell adhesion molecules. Sialic acid levels are high in human breast milk, predominately existing as N-acetyl neuraminic acid. In contrast, infant formulas contain a low level of sialic acid consisting of both N-acetyl neuraminic acid and N-glycolylneuraminic acid. N-glycolylneuraminic acid is implicated in some human in?ammatory diseases. Therefore, this article introduces readers to the distribution of sialic acid in human milk, cow’s milk and infant formula milk, the source of pure N-acetylneuraminic acid sialic acid and the effect of sialic acid on infant health, so as to provide a scientific basis for reducing the gap between formula milk and infant nutritional requirements.

Progress in the Development of Yak Dairy Products

ZHANG Lanyue, SUN Wancheng

2022, 45(2):  60-64.  DOI: 10.7506/rykxyjs1671-5187-20211129-003

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Yak milk is a characteristic resource in the Qinghai-Tibet Plateau of China. It has incomparable characteristics with other milks and has the potential to be developed into high-quality dairy products. In recent years, intensive research efforts have been made to investigate yak milk, but the development and utilization of yak dairy products in China is not perfect yet. This paper summarizes the latest progress in the development of processed yak milk products such as fermented milk, Qula, whey, cheese and butter, aiming to clarify the existing framework system of yak milk processing, find out the potential research directions and develop new yak dairy products. It is expected to provide scientific reference for the further development and utilization of yak milk resources and promoting economic development in the Qinghai-Tibet Plateau.

Research on Functional Dairy Products: Current Status and Future Prospects

ZHU Xiaopeng, LIU Yongfeng

2022, 45(2):  65-68.  DOI: 10.7506/rykxyjs1671-5187-20211202-006

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Under the background of national health, people’s health awareness increases and consumer raise higher requirements for the functionality and diversity of dairy products. With the rapid development of the dairy processing industry, functional dairy products have shown strong market attractiveness. This paper summarizes the current status of research on functional dairy products such as bovine colostrum products, probiotic dairy products, dairy products with added vitamins and minerals, dairy products with added enzymes and prebiotic dairy products, reflects on the problems existing in the research and development of functional dairy products in China, and discuss future prospects in this regard. We hope that this review can provide reference for the development of functional dairy products.