Table of Content

01 March 2021, Volume 44 Issue 2

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Basic?Research

Effect of Ripening Process on Biogenic Amines in Monascus-Fermented Cheese and Its Safety Assessment

LIU Jing, LIU Zhenmin

2021, 44(2):  1-4.  DOI: 10.15922/j.cnki.jdst.2021.02.001

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The effects of ripening temperature and time on the type and concentration of biogenic amines in Monascus-fermented cheese were examined in this paper. The results showed that tyramine, β-phenylethylamine and histamine were the typical biogenic amines of Monascus-fermented cheese during ripening. Their concentrations increased with increasing ripening time and temperature. β-phenylethylamine appeared at the late stage of maturity, and histamine appeared at high temperature. The level and growth rate of tyramine were higher than those of the other two biogenic amines, and it appeared the earliest of all. The optimal ripening conditions were found to be ripening at 14 ℃ for 12–14 days. The results of exposure assessment to biogenic amines in Monascus-fermented cheese showed that the average exposure of Chinese population was 8.55 μg/(kg·d), 94.72 μg/(kg·d) in P99. It is recommended that the per capita intake of Monascus-fermented cheese should not exceed 58 g/d in order to ensure the safety of 99.9% of populations with dietary exposure to biogenic amines through the consumption of Monascus-fermented cheese.

Processing Technology

Effect of Fish Oil on the Stability of Milk Powder for Middle-Aged and Elderly People

JIA Hongxin, YU Aimei, ZHANG Yining

2021, 44(2):  5-10.  DOI: 10.15922/j.cnki.jdst.2021.02.002

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Milk powders for middle-aged and elderly with different proportions (0%, 0.5%, 1.0% and 1.5%) of fish oil microcapsules were stored under accelerated conditions at 37 ℃ for up to 90 days. Their stability was evaluated by measuring changes in fatty acid composition, contents and retention rates of vitamin E and vitamin C, thiobarbituric acid reactive substance (TBARs) value and color during the storage period. The results showed that the addition of fish oil microcapsules had a certain effect on the stability of fatty acids in milk powder, but this effect did not show a consistent increasing or decreasing trend with the amount of added fish oil powder. The stability of fatty acids in milk powder was decreased by adding a high proportion of fish oil microcapsules; the contents of C12:0, C14:0, C16:0 and cis-9 C18:1 decreased with storage period, while the content of trans-9 C18:1 increased. Meanwhile, fish oil microcapsules decreased the retention rate of vitamin E (when added in a high proportion) and vitamin C (when added in a low proportion), increased TBARs value, a* and b*, and decreased L* of milk powder during storage. However, in general, the effect on all the above parameters except the retention rate of vitamin C was marginal. In conclusion, fish oil microcapsules can be used in milk powder for middle-aged and elderly people, meeting the requirements for the shelf stability of milk powder for middle-aged and elderly people.

Effect of Processing Parameters on Physical Properties and Microstructure of Processed Cheese Spreads

YANG Yu

2021, 44(2):  11-14.  DOI: 10.15922/j.cnki.jdst.2021.02.003

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Processing parameters are important factors influencing the physical properties and microstructure of processed cheese spreads. This work researched the influence of processing parameters on the texture, meltability, apparent viscosity and microstructure of processed cheese spreads. Results showed that shearing speed, heating temperature and heating time had significant influence on the texture and meltability of cheese samples (P < 0.05). When the shearing speed increased from 800 to 1 400 r/min, the hardness, spreading work and adhesiveness did not significantly increase. Appropriately elevating the melting temperature and prolonging the melting time enhanced the emulsifying capacity. Emulsification appeared after 2.9 minutes of shearing. The optimum processing parameters were determined as follows: preheating at 85 ℃ for 4 min under static conditions, and shearing at 800 r/min for 2.9 min. The product prepared using these conditions tasted refreshing and smooth, and had a gentle flavor, good meltability, medium hardness and good spreadability. Its sensory quality was similar to that of a commercial product.

Analysis & Detection

Determination and Exposure Assessment of Formaldehyde in Infant Formula

CHEN Tongqiang, JING Huihua, PENG Guotai, YI Shoufu, XU Wenyang, WANG Liangliang, LI Kailong, LI Can, XIANG Li

2021, 44(2):  15-20.  DOI: 10.15922/j.cnki.jdst.2021.02.004

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A method for the quantitation of formaldehyde in infant formula was established by gas chromatography (GC) and validated by gas chromatography-mass spectrometry (GC-MS). The level of formaldehyde pollution in 45 commercial infant formula samples was determined by the proposed method and the risk of dietary exposure to formaldehyde through the consumption of infant formula was evaluated. The sample pretreatment conditions were optimized and the analytical method was assessed in terms of linearity, precision, accuracy, limit of detection (LOD) and limit of quantitation (LOQ). Quantitation was performed using the external standard method. The results showed that the linearity of this method was good in the range of 0–10 μg (r > 0.999), the LOD was 0.1 mg/kg, and the LOQ was 0.3 mg/kg. The average recoveries at spiked levels of 0.3, 0.6 and 3.0 mg/kg were in the range of 88.33%–96.56%, with relative standard deviation (RSD) less than 10%. The formaldehyde content increased with increasing reconstitution temperature above 40 ℃. In order to simulate the actual consumption process, the infant formula samples were detected after being reconstituted with warm water at 40 ℃. It turned out that formaldehyde was found in all samples at levels of 0.38–2.72 mg/kg. The average formaldehyde exposure of infants of different ages was 20.40 μg/kg at 0–6 months, 21.11 μg/kg at 6–12 months and 26.74 μg/kg at 12–36 months.

Uncertainty Evaluation for the Determination of Aerobic Plate Count in Milk

JING Lijuan, WANG Yunxia, LI Cuizhi, Lü Zhiyong, LIU Lijun

2021, 44(2):  21-25.  DOI: 10.15922/j.cnki.jdst.2021.02.005

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In order to provide a scientific rationale for the quality control in the determination of aerobic plate count (APC) in milk, the measurement uncertainty was estimated. According to the national standard of China (GB 4789.2—2016), APC in samples was detected. The sources of uncertainty were analyzed according to Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1—2012) and a mathematical model for uncertainty evaluation was established. The introduced uncertainty components were evaluated and finally the total combined uncertainty was established by combination of individual components. The results showed that the extended uncertainty for APC quantification in milk samples was 0.043 4. The logarithm of APC was [3.924, 4.010], and from this, APC was calculated to be 8 395–10 233 CFU/mL. In conclusion, this procedure can effectively assess the measurement uncertainty in the determination of APC in milk.

Reviews

Recent Advances in the Application of Bioactive Polysaccharides in Fermented Milk

XU Yingrui, ZHU Yanli, MA Ruijuan, ZHAO Jun, XUE Yuantai, ZHANG Weibing, ZHANG Yan, WEN Pengcheng

2021, 44(2):  26-30.  DOI: 10.15922/j.cnki.jdst.2021.02.006

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Molecular biology studies have confirmed that bioactive polysaccharides are naturally occurring polymers that have a variety of physiological and biochemical functions. The water-complexing ability, high viscosity, antioxidant and anti-aging properties of bioactive polysaccharides lay the foundation for their application in the fields of food, and the use of bioactive polysaccharides as a bioactive ingredient in functional foods has become a current research focus. Fermented milk has good flavor and probiotic properties, but it also has the disadvantages of short shelf life, poor curd quality, and general probiotic performance. How to improve the quality of fermented milk is a current major challenge. This article focuses on recent progress in the application of different types of bioactive polysaccharides in fermented milk, and reviews the effects and mechanisms of action of bioactive polysaccharides on the physicochemical, gel and probiotic properties of fermented milk. Furthermore, it discusses future prospects for the application of bioactive polysaccharides in fermented milk. This review is expected to provide a reference for exploring the functions of bioactive polysaccharides and improving the quality of fermented milk.

Recent Progress in Research on Bioactive Peptides Derived from Fermented Milk Proteins

HONG Qing, LIU Zhenmin

2021, 44(2):  31-36.  DOI: 10.15922/j.cnki.jdst.2021.02.007

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Hydrolysis of proteins in lactic acid bacteria fermented milk produces abundant peptides. Bioactive peptides derived from fermented milk proteins not only have rich nutritional value, but also show many biological functions such as antioxidant, blood pressure lowering, and antibacterial effects. This paper reviews various biological peptides derived from fermented milk proteins with antioxidant, antihypertensive and antimicrobial activities with respect to their mechanisms of action, sequences and structure-activity relationships. Besides, it summarizes the techniques used to identify the sequences and predict the functions of biological peptides. This review will provide a reference for the development and application in functional foods.

Recent Progress in the Application of Ultra-High Pressure in Dairy Processing

GAO Xin, LI Bo, LIU Xiaojie

2021, 44(2):  37-42.  DOI: 10.15922/j.cnki.jdst.2021.02.008

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Ultra high pressure (UHP) is a new technology that puts food under high pressure above 100 MPa, which can improve food quality and kill microorganisms in food. This article summarizes the latest progress in the field of UHP dairy processing, and describes its influence on the quality of raw milk and processed milk, focusing on its advantages in promoting cheese maturation and low-fat, low-salt cheese production. The feasibility and effectiveness of UHP based dairy processing are discussed in order to provide a theoretical basis for better and wider application of UHP as well as improving the quality of dairy products.

Recent Progress in Functional Dairy Products and Functional Ingredients for Them

JIE Liang, SU Miya

2021, 44(2):  43-47.  DOI: 10.15922/j.cnki.jdst.2021.02.009

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Dairy products are widely consumed across the world due to their pleasant sensory characteristics, health benefits and nutritional properties. With the development of the food industry, it is currently a crucial trend to develop food products with more functions to improve consumer health, such as functional dairy products. This paper reviews the functions of dairy products including improving intestinal and bone health and lowering blood lipids and glucose, as well as the application of hypoglycemic ingredients in dairy products.

Comparative Analysis of Chinese and other Countries and Regions' Whey Protein Powder Standards

CHI Tao, WANG Yun, XU Xin, LIU Peng

2021, 44(2):  48-51.  DOI: 10.15922/j.cnki.jdst.2021.02.010

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This paper presents a comparative analysis of regulations and standards relating to whey protein powder in China and other countries and regions including the United States, the European Union, Canada, Australia, New Zealand, Japan and South Korea with respect to product quality indicators, contaminants and mycotoxins, and microbial limits. The quality indexes in China’s standards for whey protein powder are similar to those in other countries despite differences in some requirements. There are no differences in the requirements on mycotoxin residues, while the types and limits of contaminants are quite different. There are also some differences in the items but no difference on the limits of microbiological requirements.