| Nanguo pears are speciality fruits in Liaoning province, they are usually harvested in the early or middle of September. Nanguo pears are good taste whether fresh or processed into juice. They are enjoyed by consumers. Refrigeration is the common storage methods for Nanguo pears. Although it can can effectively extend the storage time, when Nanguo pears refrigeration after a long time, the pericarp browning during shelf life. The harvest maturity may be one important factor that influences the pericarp browning of the Nanguo Pears during the shelf life after cold storage.1-MCP treatment can delay the pericarp browning during the shelf life after cold storage, if the pears harvested too early,1-MCP will exhibite less color change and delay the sale period. If the pre-ripeness time is appropriate, it can accelerate the ripening of Nanguo Pears after cold storage, it also can reduce browning. Therefore, considering combine with harvest maturity,1-MCP treatment, pre-ripeness before storage to extend the shelf life of Nanguo pears after cold storage, reduce browning of Nanguo pears pericarp. With Nanguo pears as the tested material to study the effect of maturity on browning of pericarp. And study the effect of 1-MCP treatment on browning of Nanguo pears pericarp with different pre-ripeness time after storage(Four maturity Nanguo pears were harvested on 120、125、130、135d after flowering, corresponding to maturity Ⅰ,Ⅱ, Ⅲ, Ⅳ, pre-ripeness time were 0、5、10d). The main results were as follows:(1)With the increased of harvest maturity, the content of substance in fruit increased. But the late harvested fruit respiration and ethylene metabolism so exuberant, caused the fruit firmness decreased rapidly, fruits rotting seriously. POD activity decreased and LOX activity increased rapidly caused membrane lipid peroxidation severely, unsaturated fatty acids decreased sharply. The content of MDA and proline increased, with the increased of proline content, the relative conductivity of cell membrane increased, the activity of PPO was increased, the content of total phenol decreased, the browning index of the fruit with high maturity was higher, and the browning of Nanguo pears pericarp was more serious. The titratable acid in the maturity grade Ⅰ changed greatly on the sixth day of the shelf life, and the content of reducing sugar and soluble solid were at a very low level, the quality of maturity grade Ⅰ was poor. By comprehensive consideration that maturity grade Ⅱ and maturity grade Ⅲwere the optimum harvest maturity for long term storage.(2)Observed cell ultrastructure of Nanguo pears on the first harvest day and the sixth day of shelf life after 180 days of cold storage by electron microscopy. The results showed that: On the first harvest day, flesh cell ultrastructure of fruits collected at maturity gradeⅠ、Ⅱ and Ⅲ did not have a significant difference; maturity grade Ⅳ presented the structure of chloroplast deformable. On the sixth day of the shelf life, the cell wall of the maturity grade I crinkle bended, maturity grade II and III presented that the gap functional intercellular enlarged, organelle structure was damaged but cytoskeleton was not damaged. Maturity grade IV presented that the cell empty cavity, cell wall mesogloea dissolved, the structure of membrane was damaged, the higher of the maturity was, the more serious damage of cell ultrastructure was.(3)1-MCP treatment combine with pre-ripeness could decrease the browning index of the Nanguo pears pericarp and fruit stalk during the shelf life after cold storage, it could significantly decreased the respiration rate and ethylene production, the limacteric peak of respireation and ethylene was postponed for 9 days.1-MCP treatment combine with pre-ripeness could delay the soluble solid increased and titratable acid decreased, resisted the emergence of fruit dacay and inhabited the decrease of fruit firmness, extended the Nanguo pears storage time 12d to 20d.1-MCP treatment combine with pre-ripeness inhibited the decrease of PPO and LOX activity, then delayed the total phenol content and unsaturated fatty acid increase, resisted increase of the cell membrane electrolyte leakage、MDA content、the accumulation of praline, delayed the decrease of POD activity, reduced the peroxide action of membrane lipids.(4)The effect of 1-MCP treatment to different pre-ripeness time Nanguo pears:The indexes like activity of PPO、fruit firmness、MDA content、dacay rate、praline content of the 1-MCP treated fruits with pre-ripeness treatment for Od before storage were better than that with pre-ripeness treatment for 5d and 10d. The indexes like browning index of Nanguo pears pericarp、electrolyte leakage、titratable acid of the 1-MCP treated fruits with pre-ripeness treatment for 5d before storage were better than that with pre-ripeness treatment for Od and 10d. To the 1-MCP treated fruits with pre-ripeness treatment for Od before storage,1-MCP will exhibite less color change and delay the sale period. By comprehensive consideration the 1-MCP treated fruits with pre-ripeness treatment for 5d was suitable for long term storage.In a word, browing of Nanguo pears pericarp were related to the maturity, the fruit pericarp with high maturity was more susceptible to browning, and the quality of the fruit with low maturity was poor. So chose Nanguo pears harvested on 125d after flowering and treated with 0.75μl/L 1-MCP and pre-ripeness 5d can extend the Nanguo pears shelf life after cold storage, it could reducing the browning of the fruit after cold storage, it also can maintain fruit quality and improve the value of the goods. |
PDF Full Text Request