Table of Content

30 April 2015, Volume 38 Issue 2

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Basic Research

Acid-Producing Ability of Streptococcus thermophilus and Organic Acid Composition in Fermented Milk

CHEN Hongxia, DE Liangliang, REN Yan, ZHANG Donglei, YANG Yanrong, LIU Wenjun, ZHANG Heping

2015, 38(2):  1-5.  DOI: 10.15922/j.cnki.jdst.2015.02.001

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In the present study, 5 strains of Streptococcus thermophilus which were isolated from traditional fermented dairy products were selected to perform fermentation experiments. During the fermentation process and 504 h of storage at 4 ℃, some indexes such as fermentation time, titratable acidity (TA), pH value and viable cell counts were determined, and the composition of organic acids was tested by reverse phase high performance liquid chromatography(RP-HPLC). Fermentation and acid-producing properties of Streptococcus thermophilus were evaluated; meanwhile changes in organic acid composition and post-acidification characteristics during storage were determined. After 2 h of fermentation at 42 ℃, the pH of fermented milk by each of the five strains declined rapidly. The fermentation reached its end-point at 5–9 h, and the shortest fermentation time was required for strains IMAU10632 and IMAU20772. Over the 504 h storage period, the pH of milks fermented by Streptococcus thermophilus was reduced by about 0.5 and finally reached a stable level of about 4.2, and acids were produced at lower rates in all fermented milks until the acidity values reached levels below 90 oT , suggesting the weak post-acidification ability of the 5 strains. Furthermore, IMAU10632 was selected from these strains, which could shorten milk coagulation time, increase acid-producing rate, enhance post-acidification ability and reach a viable cell count exceeding 108 CFU/mL which remained unchanged over the entire storage period.

Physicochemical Properties of Oat Flour as Determined Using Rapid Viscosity Analyzer

WU Weidu, ZHU Hui, WANG Yaqiong, LI Yanjun, JIN Shimei, SHI Wenrong

2015, 38(2):  6-9.  DOI: 10.15922/j.cnki.jdst.2015.02.002

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Oat flour is widely used in beverage after being processed as a kind of grain. In this paper, pasting properties of starch from oat flour were studied using a rapid viscosity analyzer (RVA). Meanwhile, oat gluten was also characterized by measuring ethanol solubility index and the protein properties were determined using dilute lactic acid. The effects of different production processes for oat flour on pasting properties of starch and viscosity characteristics of gluten protein were discussed. We also determined the content of β-glucan in oat flour, which was found to have no obvious effect on the viscosity of gluten protein measured using dilute lactic acid. In addition, the peak viscosity and final viscosity measured using dilute lactic acid had obvious correlations with the final viscosity obtained from the method of ethanol solubility index showing correlation coefficients of 0.810 3 and 0.836 4, respectively, but no correlation with ethanol solubility index was observed.

Processing Technology

Optimization of Fermentation Conditions for the Production of Yoghurt Added with Puerariae radix Pulp

LIU Lili, YANG Xieli, WANG Huan

2015, 38(2):  10-14.  DOI: 10.15922/j.cnki.jdst.2015.02.003

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Yoghurt was made by fermentation of reconstructed milk mixed with Puerariae radix pulp. The optimization of four fermentation conditions (Puerariae radix pulp concentration, inoclum amount, fermentation time and temperature) for the improved sensory quality and flavonoid content of products was carried out using a combination of single factor and orthogonal array designs. The optimal fermentation conditions were 14%, 2.5%, 4.5 h and 41 ℃ for Puerariae radix pulp concentration, inoclum amount, fermentation time and temperature, respectively. The obtained product contained 1.71 mg/mL flavonoids.

Development and Stability of Beer Incorporated with Fermented Goat Milk with Added Red Date Juice

LOUXinman, WANGCunfang

2015, 38(2):  15-19.  DOI: 10.15922/j.cnki.jdst.2015.02.004

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In recent years, goat milk has attracted growing attention from consumers, which has highlighted the importance of enriching the types of goat milk products, expand the goat milk market and providing more options for consumers. A fermented alcoholic beverage with the blended flavors of yoghurt, beer and carbonated beverage was developed consisting of original beer produced by alcoholic fermentation of malt and hops with yeast and lactic acid bacteria fermented goat milk with added red date juice. The stability of the formulated beverage was evaluated based on precipitation rate and stability coefficient. The best taste and stability were achieved concurrently when the original beer was blended with the fermented goat milk added with 12% red date juice, 0.2% CMC-Na, 0.15% pectin, 0.1% sucrose ester and 4% white granulated sugar.

Reviews

Dietary Intake and Nutritional Status of Lactating Mothers in China

GUO Yanhong, SU Miya, LIU Cuiping, CHEN Wenliang, QI Xiaoyan, JIA Hongxin

2015, 38(2):  20-22.  DOI: 10.15922/j.cnki.jdst.2015.02.005

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The unified dietary reference intakes (DRIs) have been introduced in China. Nevertheless, there are wide regional variations in dietary intake and nutritional status of lactating mothers across the country, which are associated with geographic environment, life style, socio-economic and culture factors, education level, etc even within the same region. The nutritional status of both lactating mothers and their infants is influenced by maternal dietary intake. Hence, understanding of dietary intake and nutritional status of lactating mothers from different regions of China is meaningful for formulating appropriate guidelines.

A Review of Detection Methods for Cronobacter spp. in Powder Infant Formula

CHEN Wanyi, REN Jing, LIU Zhenming, GUO Benheng

2015, 38(2):  23-28.  DOI: 10.15922/j.cnki.jdst.2015.02.006

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Cronobacter spp. was originally defined as yellow-pigmented Enterobacter cloacae until 1980 when it was designated Enterobacter sakazakii, is a Gram-negative opportunistic food-borne pathogen that can cause necrotising enterocolitis, sepsis and meningitis in neonates. Neonates and infants under two months of age are at greater risk of Cronobacter infections from consuming Cronobacter spp. contaminated powdered infant formula. In 2012, the genus was reclassified to contain seven different species. Rapid and accurate identification of Cronobacter strains is important for surveillance, prevention and control of this food-borne pathogen. Moreover, this review summarizes main methods for detection and identification of Cronobacter spp., which will be of great benefit to the testing organizations in China.

Progress in Research on Main Psychrophilic Bacteria with Emphasis on Psychrophilic Bacillus in Raw Milk

XU Yu, REN Jing

2015, 38(2):  29-32.  DOI: 10.15922/j.cnki.jdst.2015.02.007

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The psychrophilic bacteria present in raw milk can grow under cold storage conditions and secrete protease and lipase which degrade milk protein and fat, resulting in the deterioration of milk quality. The present article summarizes the major species of psychrophilic bacteria in raw milk, with an emphasis on the recent progress that has been made in understanding the hazards of psychrophilic Bacillus including their species, hazard characteristics, proteases and lipases. At last, the future research direction of psychrotrophilic Bacillus is discussed.

Current Status of Research on the Structure and Function of Bile Salt Hydrolase Gene

HUANG Yanna, REN Jing

2015, 38(2):  33-36.  DOI: 10.15922/j.cnki.jdst.2015.02.008

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Bile salt hydrolase (BSH) is considered to be especially relevant for microbes that reside in the mammalian gastrointestinal tract, which also helps to reduce the blood cholesterol level of the host. This review focuses on the occurrence of bile salt hydrolase among different microorganisms and its physiological characterization, enzyme activity, substrate specificity and genetics involved with recent updates. The current perspective reveals a huge market potential of probiotics with bile salt hydrolase.