Table of Content

01 November 2018, Volume 41 Issue 6

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Basic Research

Correlation between Moderately Hydrolyzed Whey Protein and Its Allergenicity and Probiotics Growth

LU Yingying, ZHAO Lishuang, LIU Libo, LI Chun

2018, 41(6):  1-5.  DOI: 10.15922/j.cnki.jdst.2018.06.001

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Allergy to cow’s milk is an important health issue affecting infants. The main allergens of whey are α-lactalbumin and β-lactoglobulin. Moderate hydrolysis of whey proteins can significantly reduce allergenicity. However, there is currently no clear criterion for evaluating the optimum degree of hydrolysis of whey proteins. Therefore, this study aimed to establish a criterion to determine the optimal hydrolysis degree of whey proteins to reduce allergenicity and promote probiotic (Lactobacillus acidophilus 08001)growth. The results showed that the whey protein hydrolysate with a degree of hydrolysis of 14.27% reached the criterion for the optimal hydrolyzed whey protein. This hydrolysate had a significantly reduced allergenicity and better growth promoting effect on Lactobacillus acidophilus 08001.

Influence of Interaction between Functional Components and Milk Protein in Lipid-Lowering Milk on Lipid-Lowering Effect

WU Shang, LIANG Xiaona, WU Shangyi, HAN Hongjiao, KONG Fanhua, YUE Xiqing, YANG Mei

2018, 41(6):  6-11.  DOI: 10.15922/j.cnki.jdst.2018.06.002

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In order to understand the influence of interaction between the functional components and milk proteins in lipidlowering milk on the effectiveness of the functional components, we investigated the influence of casein and whey protein on the inhibitory effect of epigallocatechin (EGC) against pancreatic lipase, and we also determined the influence on the antioxidant activity of a mixture of EGC and the functional components as well as the influence on the inhibitory effect of a mixture of β-glucan and the functional components on the solubility of cholesterol-containing micelles. The results showed that milk protein could reduce the inhibitory effect of the functional components on pancreatic lipase activity, and decrease their antioxidant activity and their ability to inhibit the solubility of cholesterol-containing micelles.

Processing Technology

Preparation of Lactose-Free Yogurt and Comparison with Ordinary Yogurt

FENG Yongqiang, JIA Lingyun, HU Zhihe, WU Wenqi, ZHU Limin, LI Yaqian, FANG Qing, CHENG Kaili, ZHAO Xufei

2018, 41(6):  12-17.  DOI: 10.15922/j.cnki.jdst.2018.06.003

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The objective of this paper was to optimize the fermentation conditions of lactose-free yogurt. The level of residual sugar was used as response variable. Moreover, lactose-free yogurt and ordinary were prepared under the same conditions and their sensory characteristics were compared. Also, differences in their instrumental quality characteristics were assessed using an electronic eye, an electronic nose and an electronic tongue. The results showed that the optimal fermentation conditions were as follows: lactase dose 3.9 U/L, inoculum size 2 U/1 000 kg, fermentation temperature 43 ℃ and time 5.5 h. The lactose content of the yogurt prepared under the optimized conditions was (0.29 ± 0.07) g/100 mL. The lactose-free yogurt showed a 1.5-fold increase in lactic acid bacterial count than the ordinary yogurt (P < 0.05), but there was no significant difference in acidity or viscosity between them (P > 0.05). Principal component analysis (PCA) demonstrated no significant difference (P > 0.05) in color, aroma or taste. Therefore, compared with the ordinary yogurt, the lactose-free yogurt had no significant difference in sensory quality.

Cryoprotective Effect of Medium Components on Lactobacillus plantarum LIP-1

SHANG Yina, LI Minghui, HUO Qiwen, CHEN Jing, ZHANG Xiaoning, WANG Junguo

2018, 41(6):  18-25.  DOI: 10.15922/j.cnki.jdst.2018.06.004

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The probiotic Lactobacillus plantarum LIP-1 was cultured in modified MRS medium at high cell density to investigate the effect of changes in medium components (the types and amounts of nitrogen source, carbon source and buffer salt, total amount of carbon and nitrogen, and carbon/nitrogen ratio) on the viable cell count and survival rate after freezedrying of this strain. The optimal medium was found to be composed of carbon source (sucrose) 33.35 g/L, nitrogen source (yeast powder, soy peptone and casein peptone, 3:3:5, m/m) 10.80 g/L, and buffer salt (sodium acetate, potassium dihydrogen phosphate and sodium citrate, 2.5:1:1, m/m) 14.85 g/L (namely 0.13 mol/L). The viable cell count of strain LIP-1 cultured in the optimized medium after freeze-drying was 9.767 (lg(CFU/mL)), which was distinctly higher than that cultured in MRS medium. The modified medium allowed high-cell-density fermentation of Lactobacillus plantarum LIP-1 while maintaining its viability during freeze-drying.

Physical Properties and Formulation Design of Foods for Special Medical Purposes for Infants

ZHANG Zhaomin, ZENG Xiaolong

2018, 41(6):  26-30.  DOI: 10.15922/j.cnki.jdst.2018.06.005

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The physical properties of the raw materials used to produce foods for special medical purposes intended for infants need to be considered in the process of formulation design. In order to facilitate the formulation design and rapidly determine the amount of the major raw materials with complex chemical composition used to produce foods for special medical purposes intended for infants, some physical properties of these materials and auxiliary materials such as granularity, tap density and angle of repose were investigated. Moreover, the granularity, tap density, angle of repose and particle size distribution of commercial produced products from the formulations developed in this study were also analyzed. The results showed that all the products had identical physical properties, indicating these formulations can meet the requirements of commercial applications without modification.

Development and Antioxidant Activity of Fermented Goat Milk Added with Blueberry Juice and Mulberries

ZHAO Xuan, LI Xiangying, WANG Cunfang

2018, 41(6):  31-36.  DOI: 10.15922/j.cnki.jdst.2018.06.006

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Fermented milk was produced from fresh goat milk, blueberry juice and mulberries with added neotame and soybean oligosaccharides as sweeteners. The optimization of process parameters based on sensory evaluation, acidity and water-holding capacity was carried out using one-factor-at-a-time and orthogonal array design methods. The results showed that the optimal conditions were determined as follows: milk to blueberry juice ratio 7:3 (V/V), inoculum size 4 g/L, neotame to soybean oligosaccharide ratio 0.35:10, fermentation time 5 h, and one mulberry added to 100 mL of fermented milk. The yogurt produced under these conditions was light purple in appearance, having a uniform color embellished with purple mulberries, and it had good gelling properties and a good flavor with water holding capacity was 35%, acidity was 110 °T. Its sensory score was 95 points. The yogurt was found to contain 7.744 mg/L anthocyanidins by an ultraviolet spectrophotometric method, suggesting it to be a novel healthy goat milk product. The yogurt was determined to have potent antioxidant activity in comparison with the positive control ascorbic acid.

Analysis & Detection

High Performance Liquid Chromatography Determination of Benzoic Acid, Sorbic Acid, Saccharin Sodium and Acesulfame K in Fermented Milk and Jam

CHEN Jing, YUE Hong, LIU Chunxia, WU Lunwei, LIU Lijun

2018, 41(6):  37-41.  DOI: 10.15922/j.cnki.jdst.2018.06.007

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An high performance liquid chromatographic (HPLC) method for the determination of four sweeteners and one preservative in fermented milk and jam was developed in this paper. Water was used as the extraction solvent. The chromatographic separation was performed on a reversed phase C18 column using a mobile phase composed of a mixture of 20 mmol/L ammonium acetate buffer solution (pH 4.6) and methanol by isocratic elution. The ratio between mobile phase A and B was 85:15 (V/V) for the detection of benzoic acid and sorbic acid and 95:5 (V/V) for the detection of saccharin sodium and acesulfame K. The analytes were detected using an ultraviolet detector at 254 nm and quantified by an external standard method. The recoveries for benzoic acid, sorbic acid, saccharin sodium and acesulfame K in fermented milk at spiked levels of 1–20 mg/kg were 92.0%–102.4%, and the recoveries in jam at spiked levels of 5–20 mg/kg were 92.3%–105.8%. The limit of quantification (LOQ) for all analytes was 1 and 5 mg/kg in fermented milk and jam, respectively.

Reviews

Advances in Research on Effects of Interaction between Tea Polyphenols and Milk Proteins on Functional Properties and Bioavailability of Dairy Products

JIAO Yaoyao, ZHANG Weibing, YANG Min, ZHU Yanli, ZHANG Yan, MA Ruijuan, WEN Pengcheng

2018, 41(6):  42-47.  DOI: 10.15922/j.cnki.jdst.2018.06.008

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Tea polyphenols, secondary metabolites found in green tea, are widely used in the food and medicinal industries because of their antioxidant and anti-cancer activity and preventive effect against cardiovascular diseases. The interaction of tea polyphenols with milk proteins can alter the structure of milk proteins and further affect the functional properties and bioavailability of dairy products. There have been widespread concerns about the binding of phenolic compounds to milk proteins due to the special structures of milk proteins. This review describes the mechanism of polyphenol-milk protein interaction, the factors influencing this interaction, the characteristics of reaction products, the methods used to analyze the mechanism, and the effects of this interaction on the functional properties and bioavailability of dairy products. Through this review, we aim to lay a theoretical basis for the development of new products based on the combination of tea polyphenols and milk proteins.