Research On Cold Storage And Its Effect On The Quality Of Jimaocai(Brassica Chinensis L.)

Cold storage is one of the most common storage method. Through surveying 20 vegetable bases in 8 districts of Shanghai city and analyzing every link of cold-chain system involving vegetables, we found that harvest time, package form and variety may have a strong impact on the post-harvest quality and preservation effects. What’s more, it’s important to improve the consistency of cold-chain system and the monitoring of temperature.Based on the investigation result, we chose Jimaocai(Brassica Chinensis L.), one of the most popular vegetables by consumers, as subject and conducted a research on its intrinsic quality and the quality variation during cold storage.To observe the effect of harvest time on the quality of Jimaocai during 10-day cold storage under 4℃ in darkness, we measured the variation of water content, respiration rate, chlorophyll and carotenoid content, vitamin C content and nitrate-nitrogen content. The result showed that Jimcaocai harvested in early morning has the best quality after storage because it had the highest water content, the relative slow respiration rate in short time and the least reduction of chlorophyll, carotenoid and VC content which were 12.22%, 0.98%, 1.8%, respectively. At the meantime, by determining weight loss and a few indices above, a research on the impact of 4 package forms on the quality of Jimaocai under the same cold storage condition as above has been done. The 4 package forms were PE bag, BOPS box, foam tray plus PE film and perforated oriented polypropylene bag. It turned out that PE bag has the best performance on quality preserving considering Jimaocai’s comprehensive quality although BOPS box showed its advantage in maintaining VC content during storage. According to the result, the weight loss of Jimaocai packaged in PE bag was only 0.89% and the chlorophyll and carotenoid content decrease were only 17.92% and 6.52%. The respiration rate of Jimaocai in PE bag dropped and kept at a low level in early storage time.The evaluation of Jimaocai’s quality was based on the analysis of amino acids and volatile compounds composition. The result indicated that the composition of protein in Jimaocai is nearly perfect and the typical flavor substances in Jimcao include trans-2-hexenal, hexanal, trans-2-hexen-1-ol, isothiocyanate, nitrile, etc. Meanwhile, through comparing the quality difference among 5 varieties of Jimaocai considering their VC content, chlorophyll content, carotenoid content, ash content, crude protein content, mineral elements analysis and amino acids analysis, we can hardly find significant difference. However, we found that Jimaocai has a high nutritional value due to its abundant content of amino acids and mineral elements such as Ca, Fe, Mg, Zn, as well as its reasonable composition of protein.Our research provided a scientific basis for the effective preservation of Jimaocai and sound evaluation of its post-harvest quality.