Changes in enzyme activities and amino acids and their relations with phenolic compounds contents in okra treated by LED lights of different colors
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Publication Details
Author list: Wilawan N., Ngamwonglumlert L., Devahastin S., Chiewchan N.
Publisher: Elsevier
Publication year: 2019
Journal: LWT - Food Science and Technology (0023-6438)
Volume number: 12
Issue number: 11
Start page: 1945
End page: 1954
Number of pages: 10
ISSN: 0023-6438
Languages: English-Great Britain (EN-GB)
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Abstract
A novel and rapid method to identify contamination of Vibrio parahaemolyticus during an enrichment was developed. The principle was based on the bacteria's capability of carbohydrate fermentation and amino acid decarboxylation. Six different broths were developed with four sugar substrates, namely, dextrose (DEX), arabinose (ARA), mannose (MAO), mannitol (MAI), and two amino acids, namely, lysine (LYS) and ornithine (ODB). Bromocresol purple (BP) and phenol red (PR) were added to detect pH changes of the broths. The absorbance of the color change was determined for all sugar broths at 600 nm and both amino acids at 550 nm. Salinity and pH were adjusted to suppress competitive bacteria. The optimal conditions for the sugar substrates and the amino acids were 8% NaCl/pH = 9.0 and 6% NaCl/pH = 6.0, respectively. In real samples, this method was capable of detecting V. parahaemolyticus with a limit of detection of 0.1–1.0 log CFU/mL (measured as an initial cell concentration in the samples). At 24 h, this method also yielded a 100% sensitivity and improved a specificity to 95%–100%, compared to the 88% specificity as obtained in the conventional method. Integrating the detection of V. parahaemolyticus provided a quick and effective screening for the presence of V. parahaemolyticus. © 2019 Elsevier Ltd
Keywords
Amino acid decarboxylation, Bacterial contamination, Carbohydrate fermentation
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