Studies On Building Shelf-life Predictive Model Of Fresh Fruits

Shelf-life, also known as storage life, expiry date, etc.. Shelf-life is the length of time that the food may be stored without becoming unfit for use. It is the recommended time for which food can be stored, during which the defined quality of a specified proportion of the goods remains acceptable under expected conditions of storage and display. With the time passing by, more and more people now are paying more attention to the importance of food quality. They want to buy the food not only with beautiful appearance, good taste and high nutritional value, but also the characteristics of the products will not change for a long time, in other words, it has long shelf-life. However, all the food will experience varying degrees of deterioration during the process of storage. Therefore, we need to use the kinetic theory and mathematical model to investigate the change of food quality during storage, so as to predict the shelf-life of food better.There are numerous methods and models to predict the shelf-life nowadays, the number of methods and models that can adapt to the practical application and reflect the overall quality of the food is also quite a lot, but how to choose the most suitable one is a tough job. Three causes of corruption of fruits after harvest were analyzed in this paper, three typical representatives (strawberry, pear and kiwifruit) were selected from each corruption type (microbial infection, disease and respiratory intension), respectively. The dynamic equation of microbial growth which adapt to the type of microbial infection, the Arrhenius model which adapt to the type of disease and the Qio equation set which adapt to the type of respiratory intension were established. After that, the expression methods of shelf-life and establishment rules of predictive model were summarized. The main research results were presented as follows:1. The corruption of strawberry is related to the growth of microorganism, and Gary Mould is known as the most common and destructive disease of infection. Therefore, the microbial growth predictive model was established to investigate the relationship between the aerobic bacterial growth and the quality of strawberry. The quality changes of strawberry at 4,15,25,35? were investigated to access the relation between the aerobic plate counts (APC) changes and temperature. The kinetic model of microbial growth was developed based on modified Gompertz model. And the model was verified by several indices such as R2, Af, Bf. Comparing predicted values with observed values, bias factors and accuracy factors were all in the acceptable range. The result also indicated that the shelf-life predictive model deformed from kinetic model can predict the shelf-life of strawberry very well.2. Superficial scald, which is a physiological disease and a manifestation of pericarp senescence, is often appeared on the pears during the storage process. It's mainly caused by low temperature and high humidity. So the effect of temperature and humidity on the quality of pears was studied based on the Arrhenius equation. The quality of eight-percent-ripe'cuiguan' pear stored at different temperature (4,10, 25,35?) and different humidity (30,50,70,90%) were studied. The changes of hardness, superficial scald index, moisture content, SS content, TA content, MDA content and SOD activity of'cuiguan'pear were determined during storing process. The cross experiment under different temperature and humidity was designed. The shelf-life prediction model of superficial scald index was developed based on Arrhenius equation. The shelf-life of'cuiguan' pear can be predicted at the storage temperature from 4? to 35? and humidity from 70% to 93% based on the model.3. As a typical respiratory climacteric fruit, the respiratory intensity of kiwifruit starts to increase on the third day after harvest and reaches the respiratory peak on the 11th or 12th day. Hence, the effect of respiration intensity on the quality of kiwifruit was evaluated by using Q10 model, the quality of eight-percent-ripe'xuxiang' kiwifruits stored under different temperature (5,15,25,35?) were studied in the experiment. The results showed that low temperature could effectively inhibit the respiratory intensity and keep the descent speed of nutrition content at a lower level. Therefore, it would prolong the shelf-life of kiwifruits. Based on the Q10 model, the predictive model of shelf-life within 5-15?,15?25? and 25?35? were established, which provided a theoretical basis for the cold chain temperature control in the process of kiwifruit transportation.