Studies On Changes Of Quality Characters And Prediction Model Of Postharvest Tomato Fruit

Tomato fruit is highly favoured by the consumers for its attractive color, appealing flavor, essential multivitamins, and mineral substance. However, the fruit is soft and highly perishable, and susceptible to mechanical injury, with limiting postharvest life under ambient temperature, which has resulted in a reduced market value and limit circulation of tomato fruit. The aim of the present work was to investigate the effect of different storage temperatures on fruit colour, textural properties and sensory qualities of postharvest tomato fruit. Quality and shelf-life prediction model of postharvest tomato fruit was obtained based on above properties. The results were as follows:1. Effect of storage temperature on color changes of postharvest mature green tomato fruitThe effects of different storage temperatures (35℃,25℃,15℃,10℃,5℃and 0℃) on color changes of postharvest tomato fruits were investigated. Results showed that, a, a/b, COL value and lycopene content significantly increased with the increase of storage temperature, while L value, H°and chlorophyll content markedly decreased. Simultaneously, with increase of storage temperature, change scope of color, chlorophyll and lycopene content is also promoted. The development of chilling injury symptoms was observed during the fruit stored at 5℃and 0℃, and changes of colour parameters were not significantly impacted during storage at 5℃and 0℃. Changes of each color index was more significantly during storage at 35℃as compared to 5℃and 0℃.2. Effect of storage temperature on textural properties of postharvest mature green tomato fruitThe influence of storage temperature (33℃,23℃,13℃,8℃and 3℃) on textural properties of tomato fruit was investigated by using instrumental texture profile analysis (TPA). Fruit hardness, cohesiveness, gumminess, chewiness, adhesiveness, springiness, and the correlation coefficients between these textural parameters were measured. Results showed that, fruit adhesiveness was negative correlated with hardness, cohesiveness, gumminess, chewiness and springiness (R=-0.67～-0.81), and cohesiveness positive correlated with hardness, gumminess and chewiness (R=0.81～0.95). It is suggested that TPA parameters can be used to characterize the fruit textural quality. Storage temperature and time had a pronounced effect on the TPA parameters. Hardness, cohesiveness, gumminess and chewiness decreased exponentially during storage. Meanwhile, the increase of storage temperature promoted the decrease of fruit hardness, cohesiveness, gumminess and chewiness. Low storage temperature (3℃) is beneficial for maintaining textural quality of mature green tomato fruit after harvest.3. Effect of storage temperature on quality and physiological changes of postharvest mature green tomato fruitThe effects of different storage temperatures (35℃,25℃,15℃,10℃,5℃and 0℃) on quality and physiological changes of tomato fruit were investugated. Results showed that, fruit sensory quality and titratable acide content decrease with the increase of storage temperature, and fruit weight loss increased with the elevation of storage temperature. It is observed that Vc content and respiration rate increase first and then decrease during the while period of storage. Low temperature storage significantly inhibited respiration rate and weight loss, maintain higher levels of Vc content and sensory score. SOD, APX activity and MDA, H2O2 content significantly increased during earlier storage and then decreased during the last storage time. However, CAT activity declined during the whole storage. Low temperature storage maintains higher levels of SOD, APX and CAT activities, and lower levels of MDA and H2O2 content. These results suggest that low temperature storage could delay the senescence process and reduce the textural and flavor qualities deterioration, thereby extended the storage life of postharvest mature green tomato fruit.4. Development of quality and shelf-life prediction model for postharvest mature green tomato fruitKinetic models were developed to predict the shelf-life of tomato fruit at different temperature during storage. Fruit quality parameters H°, L value, lycopene content and hardness at different storage temperature (273.15K,278.15K,283.15K,288.15K,298.15K) were accessed to investigate the relation between the shelf-life and temperature.The kinetic models of H°, L value, lycopene content and hardness with respect to storage time and temperature were developed based on Arrhenius equation. Significantly regression coefficients (R2>0.9) indicated the acceptability of the first order reaction and Arrhenius model for predicting the changes of H°, L value, lycopene content and hardness. Activation energies(Ea) and arrhenius factor (A) of H°, L value, lycopene content and hardness were 48.09 kJ/mol and 8.93×106,67.06kJ/mol and 9.42×1010,69.20 kJ/mol and 1.38×1012, 85.90kJ/mol and 1.15×1014, respectively. It shows from the reliability assessment between predicted and observed lycopene content of tomato fruit based on L value, H°, hardness and shelf-life that relative error is with±10% calculated by the prediction model for the lycopene content, H°, hardness and shelf-life of tomato fruit. The lycopene content of tomato fruit can be predicted based on L value and the remaining shelf-life can be predicted based on H°and hardness at the storage temperature from 283.15K to 298.15K.