Table of Content

01 January 2022, Volume 45 Issue 1

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Basic Research

Analysis of Main Components and Processing Characteristics of Yunnan Milk Cake and Milk Fan By-Products

ZOU Lirong, CHEN Meng, WANG Xuefeng, PU Yuehong, DONG Wenming, HUANG Aixiang

2022, 45(1):  1-6.  DOI: 10.7506/rykxyjs1671-5187-20211117-002

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Spray-dried whey protein powders were produced from whey obtained as a by-product in the production of milk cake and milk fan as ethnic dairy products in Yunnan, and their main components and processing characteristics were analyzed. The results showed that the main components of whey protein powder obtained from the by-product of milk cake were protein 39.0%, fat 6.0%, moisture 4.1%, total ash 7.7%, acidity 23.2 °T, and pH 5.61, and the processing characteristics were 99.52% solubility, less than 3.2% precipitation at different temperatures, and emulsifying activity index (EAI) and emulsion stability index (ESI) both greater than 42.7% at different pH values. The main components in whey protein powder obtained from the by-product of milk fan were protein 72.0%, fat 19.8%, moisture 4.6%, total ash 8.1%, acidity 58.3 °T, and pH 5.20, and its processing characteristics were 98.70% solubility, less than 3.5% precipitation at different temperatures, and EAI and ESI both higher than 50% at different pH values. The sensory scores of yogurts with the two whey protein powders were 70.7 and 72.7 out of 100 points, respectively, indicating that both can be used as an ingredient in yogurt.

Comparison of in Vitro Carbohydrate Utilization by Lactobacilli and Bifidobacteria

TIAN Lulu, HUA Xu, HAN Di

2022, 45(1):  7-14.  DOI: 10.7506/rykxyjs1671-5187-20210913-010

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The growth of twelve Lactobacillus strains and six Bifidobacterium strains on a medium containing 13 carbohydrates including prebiotics (fructooligosaccharide (FOS), FOS (Vilof), xylooligosaccharide (XOS), galactooligosaccharide (GOS), short-chain inulin, long-chain inulin, isomalto oligosaccharide (IMO), stachyose, resistant dextrin, polydextrose, L-arabinose, lactitol, and erythritol) as sole carbon sources was compared using lactose as a control. Optical density at 600 nm (OD600 nm) and pH were recorded after 24 and 72 h of culture. Results showed great differences in the growth of strains on different carbohydrates. Resistant dextrin, polydextrose, and erythritol showed very limited growth promotion effects on all the strains after 24 h, probably because these strains lack the enzymes that hydrolyze glycosidic bonds. The growth promotion effects of FOS, XOS, GOS, inulin, stachyose, L-arabinose and lactitol were strain specific, presumably because of the different extracellular or intracellular enzymes secreted by each strain. Long-chain inulin slowed down the fermentation of Lactobacillus acidophilus, but was not applicable to the other strains. Despite being derived from the same source, the FOS from different manufactures showed different effects on the fermentation characteristics of strains, presumably because of the different contents of impurities they had. It was postulated that some prebiotics are beneficial to human health not by directly working on promoting the growth of lactobacilli or bifidobacteria in vivo; instead, they are degraded by other bacteria in the gut before being utilized by probiotic strains.

Characterization of Enzymes Involved in Extracellular Polysaccharide Biosynthesis in Leuconostoc citreum BD1707

LIU Jingyu

2022, 45(1):  15-19.  DOI: 10.7506/rykxyjs1671-5187-20210719-012

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Leuconostoc citreum, a Gram-positive lactic acid bacterium isolated from fermented grains and vegetables, can express various enzymes involved in the biosynthesis of different extracellular polysaccharide (EPS). In this study, Leuconostoc citreum BD1707 was cultured in tomato juice. After 24 and 72 h of culture, samples were collected for ammonium sulfate precipitation followed by in situ activity analysis using native-polyacrylamide gel electrophoresis (native-PAGE). The results showed that Leuconostoc citreum BD1707 could secrete three EPS synthases with molecular masses of about 150, 90 and 80 kDa, respectively, which were higher than those of the known levansucrases.

Analysis & Detection

High-Throughput Detection of Ochratoxin A-Producing Fungi in Dairy Products Using Gene Probe Scanning Technology

KONG Wenping, LI Yu, GUO Jincai, LI Can, ZHU Xiangcheng, CHEN Tongqiang

2022, 45(1):  20-25.  DOI: 10.7506/rykxyjs1671-5187-20210713-020

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To quickly and accurately evaluate the risk of ochratoxin A (OTA) pollution in dairy products, a method to detect fungi capable of producing OTA in dairy products was developed using gene probe scanning technology. According to the elucidated biosynthesis pathway of OTA, the halogenase gene related to OTA production was selected to design degenerate primers to establish a polymerase chain reaction (PCR) method for the detection of OTA-producing fungi. One OTAproducing strain (Aspergillus ochraceus) and five strains not able to produce OTA (Aspergillus cristatus, Aspergillus flavus, Fusarium moniliforme, Issatchenkia terricola, and Saccharomyces cerevisiae) were selected to test the PCR method. It was found that DNA from the OTA-producing strain but not the non-OTA producers could be amplified by PCR. Moreover, this method had high accuracy and sensitivity for detecting polluted dairy products.

Determination of 16 Trans Fatty Acids in Ice Cream

GONG Huili, LIU Lijun, DUAN Guoxia, LIU Chunxia, LI Cuizhi, LÜ Zhiyong

2022, 45(1):  26-32.  DOI: 10.7506/rykxyjs1671-5187-20210823-023

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A gas chromatographic (GC) method to determine the contents of 16 trans fatty acids in ice cream was established. The 2.0 g samples were pretreated sequentially with 8 mL of hydrochloric acid and 10 mL of anhydrous ethanol, separated on an SP-2560 capillary column, detected by GC with a flame ionization detector (FID) and quantified by the peak area normalization method. Under optimized chromatographic conditions, the limit of detection and limit of quantification of the proposed method were 0.012% and 0.024%, respectively, and it allowed effective separation of trans fatty acid methyl esters from cis fatty acid methyl esters and saturated fatty acid methyl esters.

Establishment and Evaluation of Control Chart for Determination of Aluminum Content in Quality Control Samples of Milk Powder by Inductively Coupled Plasma-Mass Spectrometry

NING Yuelian, LIU Lijun, HUANG Xiaoyan, HU Wenhui, YUE Hong, LI Cuizhi, LÜ Zhiyong

2022, 45(1):  33-37.  DOI: 10.7506/rykxyjs1671-5187-20210820-025

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Inductively coupled plasma-mass spectrometry (ICP-MS) was used to measure the aluminum content in the quality control sample of milk powder, and an X-control chart was established for runaway judgement and handling during the operation process. The precision and median line of the control chart for new data points obtained one year later were evaluated using Minitab software with test for equal variance and analysis of variance. The standard deviation for the previous 25 data points was 0.186 mg/kg compared to 0.126 mg/kg for the 35 new ones, while the median values of the two groups did not differ from each other. More reliable control limit was calculated based on all the data points, and the new median value was 1.334 mg/kg with a standard deviation of 0.154 mg/kg. The decrease in standard deviation suggested that the precision was improved with smaller data fluctuations. In conclusion, calculation of new and more reliable control limit from more data is useful to find obvious systematic errors, abnormal data and slow changing trend in a timely and effective way and can provide evidence to decide whether data should be retained or removed so as to directly reflect the stability and tendency of the detection.

Reviews

Development and Maturation of the Intestinal Flora during Infancy and Early Childhood and Influencing Factors

WANG Shumin, ZHAI Qixiao

2022, 45(1):  38-47.  DOI: 10.7506/rykxyjs1671-5187-20210918-011

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Infancy and early childhood are critical periods for the development and maturation of the intestinal flora. Mounting studies have demonstrated that changes in the intestinal flora during these periods may have profound effects on the growth and development, energy metabolism, maturation of the nervous and immune systems of infants and children. This article reviews the evolution of the composition and function of the intestinal flora in infants and young children during their development and maturation, as well as the factors influencing it. This article is expected to provide a reference for strategies to improve growth and development of infants and young children via regulation of the intestinal flora.

Review on Milk Oligosaccharides and Their Metabolism

GAO Shuman, PAN Yuqi, ZHANG Lizhong, DONG Yicen, LIU Xiaoming, ZHAO Jianxin, ZHANG Hao, CHEN Wei

2022, 45(1):  48-54.  DOI: 10.7506/rykxyjs1671-5187-20210823-001

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Human milk oligosaccharides have received widespread attention due to their unique probiotic effects. The composition and structure of oligosaccharides from the milks of different mammals are different. Some probiotics represented by bifidobacteria evolve a relatively complete metabolic mode of milk oligosaccharides. Compared with other prebiotics, milk oligosaccharides show more health benefits such as inducing the colonization of bifidobacteria and increasing the diversity of intestinal flora.

Effects and Mechanism of Different Stress Treatments on the Survival Rate of Lactic Acid Bacteria after Spray Drying

ZHUANG Ruoru, ZHANG Qiaoling, WANG Junguo

2022, 45(1):  55-60.  DOI: 10.7506/rykxyjs1671-5187-20210923-006

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Although the production efficiency of lactic acid bacterial starter cultures can be greatly reduced by using spray drying technology, the low viable count of spray dried starter cultures is a bottleneck currently. Therefore, this paper reviews the effects of different stress treatments on the survival rate of lactic acid bacteria after spray drying. It has been found that stress treatments stress treatments induce lactic acid bacteria to produce stress proteins to repair or degrade damaged proteins, or adjust the membrane fatty acid composition to maintain the stability of the cell membrane and regulate cellular metabolic pathways to enhance resistance, ultimately increasing the survival rate of lactic acid bacteria after spray drying. We believe that this paper will provide a theoretical reference for selecting reasonable stress treatments to improve the survival rate of lactic acid bacteria after spray drying.

Progress in Research on the Odor of Breast Milk and Infant Formula Milk Powder

JIE Liang, JIA Hongxin, CHEN Wenliang, SU Miya

2022, 45(1):  61-66.  DOI: 10.7506/rykxyjs1671-5187-20210720-009

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Breast milk is the first and only food source for meeting all nutritional needs of infants in the first stages of life and is recognized as the best form of nutrition for infant growth, development and health. In addition to providing nutrition to infants, breast milk influences infants’ taste and food preferences by exposing them to sensory experiences of various odorous compounds. In order to better apply the odor research of breast milk to infant formula milk powder, and to make infant formula milk powder more similar to breast milk, we here summarize the composition of odor compounds in breast milk and infant formula milk powder and the main factors influencing them.

Progress in the Application of Low Methoxy Pectin in Milk Products and Its Preparation Methods

LI Mengyang, ZHU Jiayi, SUN Qingshen

2022, 45(1):  67-73.  DOI: 10.7506/rykxyjs1671-5187-20210830-007

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Pectin is a natural polysaccharide present in the cell wall of higher plants, which plays an important role in the textual and nutritional properties of fruit and vegetable-based products. There are two types of pectin: high methoxy pectin (HMP, with methoxy content ≥ 7%) and low methoxy pectin (LMP, with methoxy content < 7%). LMP has good stability, gelling and thickening properties, and is widely used in dairy products since it brings a special flavor to fermented milk and increases the viscosity and stability of the product. However, the yield of LMP is low due to the limitations of production and processing conditions. Therefore, the conversion of plant-derived HMP into LMP through de-esterification can meet the industrial demand for LMP. This review outlines the current status of the application of LMP in the dairy industry and its preparation methods including acid de-esterification, alkaline de-esterification, enzymatic de-esterification and amidation, and discusses the effects of these methods on the structure of pectin. Hopefully, this review will provide a theoretical basis for the industrial production and wide application of LMP.

Current Status of India Dairy Industry and Enlightenments for China

ZHAO Xiaowei, CHENG Guanglong, PENG Hua, XU Qinghua

2022, 45(1):  74-81.  DOI: 10.7506/rykxyjs1671-5187-20210423-027

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India is the largest country in the south Asia and is also an agricultural power. Agriculture is the main income for nearly 70% of India’s population, and the contribution of animal husbandry to India’s agricultural gross domestic product (GDP) is 18%. However, due to the different religious beliefs, the development of animal husbandry, especially the dairy industry in India is unique. This paper systematically analyzes the current status of the India dairy industry in terms of dairy farming, dairy distribution layout, dairy products processing and consumption and dairy product, which is expected to be of reference significance for the high-quality and sustainable development of the dairy industry in China.