Effects And Mechanism Of Essential Oils On Quality Maintenance Of Loquat Fruit At Room Temperature

Loquat fruit (Eriobotrya japonica Lindl.), originating from south China, well known for its softness, juiciness, good taste and good nutritional value, is matured in the Wet and warm season when it’s an off season for fresh fruit. So loquat fruit has high commodity value. But loquat fruit mature in hot and rainy season, so they are susceptible to aging and badly decay when it’s stored in normal temperature after harvest. It is C. acutatum that causes most of postharvest loquat rot. At present, low temperature storage and adding chemical synthetic preservatives are most commonly used to preserve postharvest loquat fruit. Low temperature can inhibit microbial growth remarkably and restrain fruit decay, but Low temperature promotes the incidence of flesh leatheriness, which finally decreases the commodity value of loquat fruit. And chemical synthetic preservatives bring many problems such as food safety, pest resistance, environmental damage and so on. Eessential oils are widely used in the food industry, because it’s natural, safe, germicidal and antioxidative. In this paper, freshly harvested loquat fruit were used to study the preservation effect of three essential oils, carvacrol, cinnamaldehyde, linalool. Then, we investigated the mechanism from the antioxidation, fruit disease resistance and the effect of antifungal aspects to provide the theoretical basis for preservation of loquat fruit. results were as follows:(1) In the screened experiments, the optimal concentreration of essential oils had an obvious effect on the storage of loquat fruit. Decay index was obviously inhibited.fruit firmness, the TSS, Vc content and TA content were maintained at a high level. Other quality parameters were not obviously affected. However, high concentrations bringed phytotoxicity to the fruit; phytotoxicity emerged with1.0μ L/L-cinnamaldehyde,2.5μL/L-carvacrol and5.0μL/L-linalool. We selected the optimal econcentration of the three essential from the test, as follows:carvacrol-1μL/L, cinnamaldehyde-0.5μL/L and linalool-lμL/L. (2) Obvious effects on antioxidant systems were determined in postharvest loquat fruit treated with the three essential oil, including an increase of the activity of antioxidant-related enzymes SOD, POD, APX, CAT and antioxidant substances total phenolics, total flavonoids. At the same time, the essential oil treatment improved DPPH radical scavenging activity, hydroxyl radical scavenging activity and reducing activity and restrained the production of superoxide anions. The mechanism of the three essential oil to decrease fruit decay index may be related to the increase of antioxidant activity to improve free radical scavenging capacity and delay the fruit senescence.(3) The three plant essential oils could significantly inhibit the extension of lesion diameter and improve the activities of disease resistance-related enzymes PAL, POD, PPO, chitinase and β-1,3-glucanase in the loquat fruit which had been inoculated by C.acutatum. The three suitable concentration of essential oils had an antifungal effect on C. acutatum in vitro. As the oil concentration increased, the inhibition rate increased, spore germination and germ tube length decreased. So we can conclude from the three chapters that three essential oil may decrease fruit decay by the synergy effect of enhancing fruit antioxidant capacity, improving fruit disease resistance mainly and direct antifungal effect partly.