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Phenolic extract from banana peel was extracted with 95% ethanol and characterized by LC-TOF-MS/MS. Epicatechin, rutin, 3,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzoic acid, myricetin, ferulic acid, chlorogenic acid, and gallic acid were detected in the extract. Cholate test was performed for the initial examination of the hypolipidemic effect of the dietary fibres. The dietary fibres prepared by sequential treatment with sulphuric acid then sodium hydroxide (SST) and sodium hydroxide treatment (SHT) had high water-holding capacities (7.48 and 6.91 g g−1) and swelling capacities (4.8 and 4.3 ml g−1). The dietary fibres prepared by sequential treatment with trypsin then sulphuric acid (TST) and sulphuric acid treatment (SAT) had high oil-holding capacities (5.52 and 5.10 g g−1) and enhanced capacities for sodium cholate adsorption. Results indicated the potentials of banana peel as functional ingredient in food applications.

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Acta Alimentaria
Authors: R.D. Wang, Y.J. Deng, L.J. Sun, Y.L. Wang, Z.J. Fang, D.F. Sun, Q. Deng, and R. Gooneratne

Growth and haemolytic activity of several pathogenic Vibrio species were compared in egg-fried-rice with different egg ratios. Egg-fried-rice preparations with rice-to-egg ratios of 4:1, 1:1, and 1:4 were inoculated with either Vibrio parahaemolyticus, V. cholerae, V. vulnificus, or V. alginolyticus and incubated for 24 h. Cell number, thermostable direct haemolysin (TDH) activity, and total haemolytic activity were determined. The cell number and total haemolytic activity increased in all Vibrio strains after 24 h, and these were most marked in egg-fried-rice with the highest egg content (1:4 (rice:egg) ratio; P<0.05). V. alginolyticus exhibited the maximal growth and V. parahaemolyticus the highest haemolytic activity, but only V. parahaemolyticus ATCC 33847, V. alginolyticus CAMT 21162, and V. alginolyticus HY 91101 showed TDH activity. Results suggest that lowering egg content in egg-fried-rice could reduce growth and virulence of Vibrio pathogens.

Open access

Shewanella putrefaciens supernatant was found to increase the virulence factors of Vibrio parahaemolyticus by efficiently degrading its acylhomoserine lactone (AHL). To further reveal the regulation mechanism and its key degrading enzyme, a potential AHL-degrading enzyme acylase (Aac) from S. putrefaciens was cloned, and the influences of temperature, pH, protein modifiers, and metals on Aac were tested. Aac was significantly influenced by temperature and pH, and exhibited the highest AHL-degrading activity at temperatures of 37 °C and pH of 8. Mg2+ and Fe2+ can further increase the AHL-degrading activity. 10 mM EDTA inhibited its activity possibly by chelating the co-factors (metals) required for Aac activity. Tryptophan and arginine were identified as key components for Aac activity that are critical to its AHL-degrading activity. This study provides useful information on Aac and for V. parahaemolyticus control.

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Acta Alimentaria
Authors: M.Y. Jiang, Z.R. Wang, K.W. Chen, J.Q. Kan, K.T. Wang, Zs. Zalán, F. Hegyi, K. Takács, and M.Y. Du

After suffering from mechanical injury and fungal infection, grapes are perishable. Botrytis cinerea, the causal agent of gray mould, is a critical pathogen for grapes. In this study, the inhibitory effect of Pseudomonas fluorescens on the formation of gray mould on grapes during the postharvest storage was investigated on “Kyoho” grape. The results suggest that a living cell suspension of P. fluorescens significantly inhibited spore germination of B. cinerea, and significantly reduced the incidence of grape gray mould. Moreover, compared with the control, the fruit inoculated with P. fluorescens had elevated activities of polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), phenylalanine ammonia-lyase (PAL), chitinase (CHI), and β-1,3-glucanase (GLU). Increase in enzyme activity correlated with enhanced host resistance. In addition, there was little difference in storage quality between the treated group and control group, indicating no adverse effects of the induced defence response on fruit quality.

Open access
Acta Alimentaria
Authors: E. Horvath-Szanics, J. Perjéssy, A. Klupács, K. Takács, A. Nagy, E. Koppány-Szabó, F. Hegyi, E. Németh-Szerdahelyi, M.Y. Du, Z.R. Wang, J.Q. Kan, and Zs. Zalán

The increasing consumer demand for less processed and more natural food products – while improving those products’ quality, safety, and shelf-life – has raised the necessity of chemical preservative replacement. Biopreservation refers to extended storage life and enhanced safety of foods using the natural microflora and (or) their antibacterial products. Chitinolytic enzymes are of biotechnological interest, since their substrate, chitin, is a major structural component of the cell wall of fungi, which are the main cause of the spoilage of food and raw plant material. Among the several organisms, many bacteria produce chitinolytic enzymes, however, this behaviour is not general. The chitinase activity of the lactic acid bacteria is scarcely known and studied.

The aim of the present study was to select Lactobacillus strains that have genes encoding chitinase, furthermore, to detect expressed enzymes and to characterise their chitinase activity. Taking into consideration the importance of chitin-bindig proteins (CBPs) in the chitinase activity, CBPs were also examined. Five Lactobacillus strains out of 43 strains from 12 different species were selected by their chitinase coding gene. The presence of the chitinase and chitin-biding protein production were confirmed, however, no chitinolytic activity has been identified.

Open access