‘Red Globe’ table grapes are large, edible, seeded fruit with firm flesh that tastes good, but can have poor postharvest shelf-life. This study was conducted to explore the effects of products of Lactobacillus delbrueckii subsp. bulgaricus strain F17 and Leuconostoc lactis strain H52 on ‘Red Globe’ table grapes for the enhancement of shelf-life and improvement of grape quality characteristics during postharvest storage. Strains F17 and H52 were isolated from traditional fermented yak milk obtained in the Qinghai–Tibetan Plateau. Samples from untreated and treated grapes were analyzed for physicochemical, biochemical, and microbiological properties (weight loss, decay rate, pH, total soluble solids content, titratable acidity, total phenols, sensory evaluation, and microbial growth) for 20 days. The results demonstrated that supernatants from both strains significantly reduced weight loss, decay rate, aerobic mesophilic bacteria, and coliform bacteria counts; delayed maturity and senescence of table grapes; and reduced titratable acidity and total phenols. However, the supernatant of strain F17 was more effective and resulted in better sensory evaluations and had a significant inhibitory effect on yeast and molds by day 5. Meanwhile, the supernatant from strain H52 had a significant inhibitory effect on fungi over the whole storage period. In addition, the results of the Pearson correlation analysis suggested that weight loss, decay rate, total soluble solids content, and microorganisms were highly correlated with the sensory evaluation data and quality of postharvest grapes when treated with the products of strain F17. On the basis of these data and sensory organoleptic qualities, the supernatant containing products from strain F17 had the best potential as a biopreservative to improve the postharvest quality of ‘Red Globe’ table grapes.
Abstract-The endophytic N-fixing microbes Klebsiella oxytoca NHglj1, Klebsiella oxytoca NHglj2 and Enterobacter asburiae LMw107 of Nitraria were selected to explore the effect of Nitraria schoberi L. plant sap on salt and alkali resistance of its 3 endogenous N-fixing microbes strains in the Winogradsky's N-free medium under different salinity and alkalinity gradient. The results show that the NaCl tolerance of 3 strains is 0 ~ 4% and 3 strains can all survive in pH 6 ~ 13. After sap of Nitraria is added, the salt resistance of NHglj1 decrease, the colony diameter of K. oxytoca NHglj1 is 59% ~ 82% that of control, the change of alkali resistance of NHglj1 is similar to that of the salt resistance, the diameter of NHglj1 is 13% ~58% that of control (P<0.05). However, the salt resistance of NHglj2 and LMw107 increase, the diameter is larger than 2 %~ 45% that of the control. The alkali resistance of NHglj2 and LMw107 also increase in pH6~13. The results exhibit that Nitraria sap may partially improve salt-alkali resistance of parts of endogenous N-fixing microbes.
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