Chemistry of enzymatic browning in longan fruit as a function of pericarp pH and dehydration and its prevention by essential oil, an alternative approach to SO2 fumigation.

BACKGROUND: Longan fruit is a rich source of bioactive compounds; however, enzymatic browning of pericarp and microbial decay have limited its postharvest life. SO2 has widely been used to overcome these limitations; however, due to safety and regulatory concerns, alternative means should be identified. In this study, antioxidant and antimicrobial properties of thymol (TH) essential oil were investigated against the enzymatic browning and decay of longan fruit. METHODS: Fruits were coated with TH (4%) for 5 min, sealed in polyethylene (PE) packages and stored at 4 °C for 42 d. Fruits immersed in distilled water (DW) and stored in PE were used as control. RESULTS: TH extended the postharvest life of longan to 42 d than 28 d in DW. TH residues decreased from 142 to 11.17 mg kg-1, while no residues were found at day 42. TH significantly (P ≤ 0.05) reduced the respiration rate, inhibited polyphenol oxidase (PPO) and peroxidase (POD) enzyme activities, sustained high phenols/flavonoids and prevented pericarp browning (BI) than DW. TH also effectively (P ≤ 0.05) maintained the color values, firmness of peel and aril, total soluble solids (TSS), titratable acidity (TA), inhibited decay incidence (DI) and resulted in lower ethanol content than DW. BI as a function of pericarp pH was highly correlated; pH and BI (r = 0. 97), with PPO (r = 0.93) and with water loss (r = 0.99). A high coefficient of correlation of BI was found with the pericarp pH, enzymes, phenolic, water loss and decay incidence with ethanol. TH could be the best alternative to SO2 and other synthetic preservatives.

Brevibacterium hankyongi sp. nov., isolated from compost.

A Gram-positive, strictly aerobic, non-motile, milky-white to creamy coloured and rod-shaped bacterium, designated BS05T, was isolated from compost. Phylogenetic analysis based on 16S rRNA gene sequence comparison revealed that the strain formed a distinct lineage within the genus Brevibacterium and was most closely related to Brevibacterium avium NCFB 3055T (96.3 %), Brevibacterium oceani BBH7T (96.2 %) and Brevibacterium epidermidis NBRC 14811T (96.1 %). The DNA G+C content was 62.3 mol%. The predominant quinone was MK-8(H2). The major fatty acids were anteiso-C15 : 0, anteiso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. The cell-wall peptidoglycan of strain BS05T contained meso-diaminopimelic acid. The major polar lipid was phosphatidylglycerol. Moreover, the low sequence similarity of the 16S rRNA gene sequencing, physiological, biochemical and chemotaxonomic analyses allowed the phenotypic and genotypic differentiation of strain BS05T from the recognized species of the genus Brevibacterium. Therefore, strain BS05T represents a novel species of the genus Brevibacterium, for which the name Brevibacteriumhankyongi sp. nov. is proposed, with the type strain BS05T (=KACC 18875T=LMG 29562T).