Effects Of Postharvest Factors On Tomato Rot And Quality During Shelf Life

Fresh tomato plays a very important role in the vegetable supply of China, but as a sort of large berry fruit having rich nutrient, tomato is easily damaged and infected in the course of harvest, transport, storage and market. Therefore, it is extremely useful to study the occurrence regularity and relative control technologies of post-harvest diseases, so as to keep tomato good quality, prolong the shelf-life of products and reduce loss in the storage and market. This study depends on the fund of Project"HT-99-081"named"Reducing Spoilage and Contamination Risks of Fresh Vegetables in China and Australia"of Australian Centre for International Agricultural Research (ACIAR), in order to research effects of post-harvest factors on tomato rot and qualtity during storage. These main results of this study show as follows:1. Effects of tomato culticar (Jinguan No.1, FA189 and Zhongza 9) and the postharvest facters including time (1～7d), temperature (4℃±1℃and 26℃±1℃) and package condition (packed by PE film and unpackaged) on the tomato rot caused by Botrytis cinerea Pers were investigated in this experiment. The results showed as follows: inoculation dose and time were extremely significant factors for tomato diseases. There were significant effects of tomato cultivars on disease degree (p<0.05) while no evident impact on disease incidence (p>0.05), and among three cultivars disease degree of tomato"Jinguan No.1"was the most severe; the storage temperature and package conditions were all significant factors (p<0.05) for disease incidences and degrees, of which low temperature storage was beneficial to reduce and relieve diseases, but under package condition tomatoe disease tended to become worse. According to the total statistic analysis, the effect trends of risk factors were that: inoculation dose > time > temperature > package > cultivar. Therefore, decreasing the amount of initial disease microbes on the fruit surface was the basis of reducing tomato rot of postharvest.2. Effects of different washing treatments on tomato rotten rates within 7 days shelf-life, packed by PE film at ambient temperature (28-30℃), were investigated, including tap water, 100mg/kg NaClO and 5mg/kg ClO2 under different temperature (5℃higher and lower than fruits, respectively). The results showed that the rotten rates of the washed tomatoes were decreased significantly from 47 % (no washed, CK) to 9%-25% (p<0.01); and when the fruit temperature was 28-29℃, the temperature had no evident effect of tap water and ClO2 treatments on reducing rotten rate of tomato, however, it reduced the rotten rate significantly by 100mg/kg NaClO washing treatment with 5℃higher than fruits'temperature compared with 5℃lower temperature treatment(p<0.05), which reached 9%, the best treatment after 7 days storage. Generally speaking, the rotten rate of the tomatoes treated by NaClO were significantly lower than those by ClO2 and tap water treatments (p<0.05).3. The effects of temperature (4℃±1℃, 10℃±1℃and 30℃±1℃), package (airtight package, package with two holes and unpackaged) and time (0, 3, 6, 9 and 12d) on the tomato quality were investigated in this experiment, including weight loss, firmness, fruit surface color, sugar-acid ratio and content of lycopene; Then, the grey relational grade analysis was applied to study the effects of various storage conditions on comprehensive quality of tomato, and build the predictive models of tomato quality during storage depending on time and temperature. The results were attained as follows: there were both extremely significant (p<0.01) effects of storage temperature and time on all tomato quality indexes, and also package on weight loss, firmness and content of lycopene; however, effects of package on sugar-acid ratio and a/b were not significant (p>0.05). Predictive models of response surface on weight loss, firmness, a/b, sugar-acid ratio and content of lycopene were built respectively, and their R2 values ranged from 0.7824 to 0.9911, and the lack of fit were not significant. Finally, predictive models of the comprehensive quality were gotten: for losed package, G1=0.1953+0.0406x₁+0.0228x₂-0.0021x₁²+0.0001x₁x₂-0.0006x₂²; for package with hole, G₂=0.2207 +0.0525x₁ +0.0217x₂-0.003x₁² +0.0002x₁x₂-0.0005x₂²; for no package, G3=0.1672+0.0413x₁+0.0173x₂-0.0021x₁²+0.0002x₁x₂-0.0002x₂². Moreover, the models above were verified by experiment at 20℃±1℃and showed well capability of estimating tomato quality changes during storage.