Study On The Low Temperature Storage Of Lettuce

To reduce problems of the post-harvested lettuce such as fibration, growing mildew and decaying, this dissertation explored the optimal temperature for the lettuce storage and the effects of the coating, the combination of gibberellin acid and ozone and ozone storage on the quality of the lettuce. The possible mechanism for the lettuce storage technology and theory were also studied.The results were as follows:1. To obtain the optimal temperature for the lettuce storage, the effects of different temperatures (such as 1℃, 3℃, 5℃and 7℃) on the quality of the lettuce were studied according to the indices of respiratory intensity, Vc content, weight loss rate,and cellulose levels. The results preliminarily showed that the lettuce stored at 5℃had lower respiratory rate, cellulose levels and weight loss rate and more Vc content than stored at the other temperatures.2. PE package was used to maintain the quality of the lettuce which was stored at a low temperature of 5℃in this chaper. As a result ,the Vc content, cellulose levels ,chlorophyll contents, weight loss rate, soluble complex and PPO activity of the PE package of lettuce were lower than that without PE package. The result showed that PE package was available to maintain good quality of lettuce.3. Calcium chloride aqueous solution was used to treat lettuce in order to solve the problems of lose green and wet rot during the later storage time to extend the shelf life . The study on the effects of treatment of Calcium chloride aqueous solution combined with PE package on lettuce indicated that the optimized treatment condition is Calcium chloride aqueous solution concentration 2%～6% and soak time 2～6min.4. Studying on the quality of lettuce treated by ozone(treating time containing 5 minutes,10 minutes and 15 minutes) combinated with PE package . The result indicated that the optimal content of the treating time of ozone is 5 minutes. Because it can prolong the storage time and keep in a good condition.5. Selected the concentration of Calcium chloride aqueous solution,the treatment time of ozone and the soak time of Calcium chloride aqueous solution as treating factors to conduct L₉(3⁴)orthogonal experiment.. Results indicated that the treatment of Calcium chloride aqueous solution combined with ozone could restrain a good quality of lettuce effectively and prolonged the preservation period. It would still well maintained the nutrition and appearance qualities of lettuce after 28 days storage .