Studies On Prediction Models For Fruit Decay And Shelf-Life Of Postharvest Strawberry

Strawberry was popular with consumers becaue of its brightly color, flavored taste and highly-nutrition.However, moisture content of fruit is rich, and fruit is soft and highly perishable, susceptible to mechanical injury, physiological deterioration, water loss and microbiological decay.The loss is heavy in recent years because of the large yield of strawberry fruit and the loss during storage and transportation.It is crucial to monitor the change of quality after harvest in time.In this paper, kinetic model of decay index, shelf-life prediction model and decay index prediction model based on ethanol content were developed on the basis of the study of decay index changes of strawberry fruit at different temperatures during storage.The theory evidence used for monitoring of quality of strawberry fruit during circulate can be provided from this paper. The results were as follows:1. Quality and decay changes of strawberry fruit at different storage temperaturesThe quality and decay changes of eighty-percent-ripe strawberry fruit (Fragaria×ananassa Duch.) stored at 273,278,283,288, and 293K were studied. It was found that the TPA parameters, fruit firmness, cohesiveness, springiness, resilience and chewiness, decreased, whereas adhesiveness increased during storage in each temperature. The significant correlation relationship between six textural parameters was also confirmed. Significantly and positively correlations among fruit firmness, cohesiveness, springiness, resilience and chewiness, while fruit adhesiveness had negative correlations with other texture parameters were also found. The development of colour at all tempetures was normal. Lightness of the fruit was not affected by storage time at 273K, but declined slightly with higher storage temperatures. Chroma and hue values remained similar at 273K, but decreased at higher temperatures. Increased storage temperature resulted in accelerated decrease in fruit quality loss and increase of decay index. Low temperature inhibited the decrease of TSS,TA,VC,total sugar and reducing sugar and the increase of decay incidence, thereby delayed senescence process and quality loss and prolonged storage life of strawberry fruit. The increase of decay is the main factor that shortened the shelf-life of postharvest strawberry. 2. Kinetic model of decay index and shelf-life of strawberry fruitTo study decay changes and shelf-life of postharvest strawberry, kinetic model of decay index and shelf-life prediction model were developed at different temperatures during storage. The value of decay index at different storage temperatures (273,278,283,288,293, 298K) were determined. The high regression coefficients(R2>0.9) indicated the acceptability of the zero order reaction model for predicting the changes of decay index value. The kinetic models of decay index value with respect to storage temperature and time were developed based on Arrhenius equation. Activation energies (Ea) and rate constants (kf) of kinetic model of decay index were obtained. They were 59.50 kJ/mol, 3.15×1011, respectively. The shelf-life prediction model and kinetic model of decay index were verified at different temperatures (275,280,285,290,295,300 K) and the results were acceptable. The remaining shelf-life of strawberry fruit can be predicted at the storage temperature from 273 K to 300 K based on decay index value.3. Prediction model for decay index of strawberry fruit based on ethanol contentIn order to monitor the decay situation of strawberry fruit during storage and transportation, prediction model for decay index based on ethanol content was developed. The development of decay index and ethanol content of strawberry fruit stored at different temperatures(273,278,283,288,293 and 298K) were determined. The kinetic model of ethanol content with respect to storage time and temperature was developed based on the Arrhenius equation and Activation energies (Ea) were 57.48kJ/mol Prediction model for decay index of strawberry fruit based on ethanol content was proved to be fit for the linear equation (R2=0.9778). The two models mentioned above was verified with the strawberry fruits stored at 275K,280 K,285 K,290 K,295K and 300K.and the Determination Coefficients (R2) all were 0.99 and the Relative Prediction Error were 0.76%,7.08%, respectively and the results showed that the prediction were acceptable. The prediction values of decay index obtained from the kinetic model of decay index were proved to be more precise compared with those from the prediction model for decay index of strawberry fruit based on ethanol content (RE=5.89%<7.08%). The results showed that decay index of strawberry fruit can be predicted at the storage temperature from 273K to 300K based on ethanol content.