Study Of Fresh-keeping Effect Of Extract Of Ginkgo Biloba L. Leaves On Fresh-cut Apples

In order to develop new natural preservations of fruits and vegetables,‘redFuji’ apples were used in this paper, and total flavonoids used as target activeingredient of extracts of Ginkgo biloba leaves, the fresh-keeping effect of extracts ofGinkgo biloba leaves and with alginate-coatings on preservation of fresh-cut appleswere investigated. Design orthogonal experiment to optimize ethanol extractconditions of flavonoids from Ginkgo biloba leaves assisted by ultrasonic. To findthe best concentration, fresh cut apples were immersed in solutions of differentconcentrations of Ginkgo biloba leaves extracts, and with alginate-based film. Thenfresh-cut apples were stored at4℃and evaluated by physiological and biochemicalindicators and sensory evaluation. And study the effect Ginkgo biloba leavesextracts on polyphenol oxidase of apples.The main results were as follows:1. Optimum extraction combination of total flavonoids of Ginkgo biloba leavesis with:90%ethanol,1:20of solid-liquid ratio,70℃, and400w of ultrasonic power.According to the results of variance analysis, temperature had the greatest influenceon extraction yield of total flavonoids of Ginkgo biloba leaves extracts (p<0.01),followed by ethanol concentration, ultrasonic power is minimum (p>0.05).2. Fresh-cut apples were immersed in Ginkgo biloba leaves extracts with fourflavonoids concentration of0,0.25mg/mL,0.50mg/mL,0.75mg/mL, respectively.Results showed that Ginkgo biloba leaves extracts could reduce the respiratory rateand ethylene release quantity, polyphenol oxidase (PPO) and peroxidase (POD)activity of fresh-cut apples, inhibit browning, reduce moisture loss delay reductionof soluble solids, titratable acid and VC content, and maintain hardness, control theamount of microorganisms on apple surface at low levels, improve quality offresh-cut apples. And Ginkgo biloba leaves extracts with flavonoids concentration of0.50mg/mL showed the best effect.3.Compared fresh-cut apples treated with sterile distilled water (CK1),fresh-cut apples treated with alginate-based coating(CK2), alginate-based coating with Ginkgo biloba leaves extracts (A) and Ginkgo biloba leaves extracts(B), couldreduce respiratory rate, ethylene release, PPO and POD activity, delay soluble solids,L*value, titratable acid and VC content fall, and slow down quality loss andhardness drop, inhibit microbial growth, maintain the sensory quality of fresh-cutapples during storage. Fresh-cut apples of A treatment showed best effect.4. The effect of flavonoids of Ginkgo biloba leaves on PPO of ‘red Fuji’ appleswhich were extracted by frozen acetone was studied. Results showed that Ginkgobiloba leaves extracts has obvious inhibitory effect, the total content of flavonoids in0~0.2μg/mL, with the increase of Ginkgo biloba leaves extracts concentrationenzyme activity declined rapidly and at content of0.2~0.4μg/mL, with theincrease of extract concentration enzyme activity decreased slowly. The inhibition ofGinkgo biloba leaves extracts on PPO is noncompetitive and reversible.