| Fresh strawberry fruits are highly perishable fruits due to their physiological and morphological properties, and their rapid postharvest responses. Because of their extreme tenderness, vulnerability to mechanical damage, to high level of respiration and their susceptibility to fungal spoilage, they have a very limited postharvest life and poor quality. Microbial biocontrol agents have shown great potential as alternatives to synthetic fungicides for the control of postharvest decay of fruits and vegetables have attracted the attention of many researchers and been extensively studied. So far, no reports have mentioned Hanseniaspora uvarum as biocontrol agent combined with salicylic acid, calcium, sodium bicarbonate treatments against fungal spoilage on strawberries and they can further improve decay control and the postharvest quality of strawberries. In our study, the effect of antagonistic yeast H. uvarum, alone or integrating with refrigeration (2±1℃) and salicylic acid, calcium, sodium bicarbonate, GRAS substances, respectively, on improving biocontrol, reducing spoilage, preserving the postharvest quality of ’Fragaria ananassa Duch’ strawberries were investigated.The contents and results are as follows:Concentration of washed cell suspension of H. uvarum at1×109、1×108、1×107、1×106、1×105CFU·ml-1, Botrytis cinerea at1×105CFU?ml-1and sterile distilled water as a control was added to each wound on the strawberry. The higher the concentrations of H. uvarum the smaller the lesion diameter and infection rate, but there was no significant difference between1×108and1×109CFU·ml-1. When the concentrations of H.uvarum was at1×108CFU·ml-1or1×109CFU·ml-1, the lesion diameter and infection rate of the fruits treated with H. uvarum was distinctly better than others treatments. So we chose the antagonist yeast at concentration of1×10CFU·ml-1combined with different concentration of salicy acid, calcium chloride, sodium bicarbonate spray during the next two experiments (spray and artificial inoculation).♂In our study, we found that H. uvarum at1×108CFU?ml-1combined with100μig?ml-1salicy acid,2.0%calcium chloride,2.0%sodium bicarbonate, respectively, were significantly reduced the diameters of the rotten lesions and the infection rate of the strawberries.The experiment was carried out in part to evaluate the effects of different substances combined with antagonistic yeast H. uvarum on quality and decay index of strawberry fruit. Strawberry fruit was stored under the conditions of air temperature at (2±1)℃and relative humidity(RH) at95%. Decay rate, weight loss, change color contents of soluble solids, reducing sugar, soluble protein, Vc and titratable acid were investigated regularly. The experimental results showed that, compared to the control, H. uvarum alone or combined with salicylic acid, calcium, sodium bicarbonate, respectively, could decreased the rate of natural infection and decay rate. H. uvarum combined with salicylic acid, calcium, sodium bicarbonate, respectively, could delay the decrease of weight loss, change color, soluble solids, reduing sugar, soluble protein, Vc, titratable acid and keep the fresh quality to prolong shelf-life of strawberry fruit. But the efficacy of biocontrol agent and the quality of postharvest strawberries were different according to different substances. Textural parameters of hardness, springiness, adhesiveness, cohesiveness, resilience, gumminess and chewiness were investigated.The experiment was also carried out in part to evaluate the effects of different substances combined with antagonistic yeast H. uvarum on physiological characteristics of postharvest strawberry fruit. Malondialdehyde (MDA) content, superoxide anion (O2), activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), polyphenoloxidase (PPO) were investigated regularly. The experimental results showed that H. uvarum alone or combined with salicylic acid, calcium, sodium bicarbonate, respectively, could delay the accumulation of MDA and O2, increase the activities of CAT, POD, SOD, APX, PAL and distinctly inhibited the activity of PPO to postpone the senescence of strawberry fruit. Effects of different substances combined with antagonistic yeast H. uvarum on the activity of defense enzyme of postharvest strawberry fruit were evaluated. The experimental results showed that H. uvarum combined with salicylic acid, calcium, sodium bicarbonate, respectively, could increase the activities of PAL and (β-1,3-glucanase of strawberry fruit. The reduction the fruit postharvest diseases by the combined treatments were positively correlated with higher activities of PAL and (β-1,3-glucanase in strawberries. |
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