Study On Storage And Preservation Of Daemonorops Margaritae Shoots Under Low Temperatures

With the aim of providing theoretical and practical foundations for storage and preservation of Daemonorops margaritae shoots through exploring the physiological and biochemical mechanisms affecting the storage of the shoots, changes in apparent quality, relative electronical conductivity, percentage of weight loss, contents of Vc, reductive sugar and total sugar, and activities of POD, CAT and PPO of the shoots stored under the following four temperature treatments of 3, 7, 11 and 25°C were systematically studied with raw materials harvested from a plantation for edible shoot production in Xiegang Forest Farm, Dongguan City of Guangdong Province. The study results are shown as follows:1. The fresh shoot of D. margaritae contains about 90% of water. The contens of Vc and soluable protein are 1.88g/100g and 18.6 mg/100g respecyively in terms of freash weight, while the reductive sugar, total sugar and cellulose account for 0.12%, 3.51% and 0.8%. D. margaritae shoot can be served as a kind of good natural healthcare food. It can be seen as a best-quality vegetable for the people suffering from diabetes.2. The apparent quality of D. margaritae shoot varied with changing temperutres. Low temperures (3, 7, and 11°C) restrain the activity of microorganisms, leading to less damage of shoots by microorganisms and keeping the color and luster of the shoots bright. The chromaticity of the shoots trend to decrease with increasing period of storage. The decreasing ranges of brightness and color and luster of the shoots stored at 7°C and 11°C did not exceed 10%. The shoots stored at 3°C and 7°C suffered from chilling damages on the 14th day and 21st day after storage. The storage temperutre of 11°C is therefore the best temperutre keeping the shoots in good apparent quality.3. On the whole, the hardness, percentage of weight loss and relative electronical conductivity increased with increasing period of storage. The shoots stored under low temperatures (3, 7, and 11°C) recorded highest values of hardness. The percentage of weight loss of shoots decreased with increasing temperatures. The percentages of weight loss of shoots stored under low temperatures was less than 4.5%, while that at the highest temperature of 25°C was higher than 10.5%. The relative electronical conductivity of shoots stored at 3°C had been higher than those at 7°C and 11°C, due to the destruction of cell membrane caused by chilling damages under low temperatures.4. The contents of Vc, reductive sugar and total sugar decreased with increasing period of storage. Low temperature storage restrained the decrease in contents of Vc, reductive sugar and total sugar of the stored shoots, thus improved the quality of the shoots. The content of reductive sugar of shoots stored at 3°C increased rapidly in the first week to prevent the shoots from chilling damage. The content of soluble protein decreased during the first two weeks and increased gradually thereafter. The content of soluble protein of shoots stored at 11°C was higher than those at 7°C and 3°C as a whole. The contents of cellulose of the shoots stored under different temperatures showed an increase with increasing period of storage, in the order of increment of 11°C >7°C >3°C >25°C.5. The activities of CAT of shoots stored under different temperatures increased first and then decreased, forming single-peak curves with peaks occurred on the 7th and 14th days after storing. The acitivity of PPO of shoots showed an overall increase under different temperatures, with the nighest value recorded at 25°C, followed by those at 11°C and 7°C. The The acitivity of PPO of shoots stored at 3°C reached the highest value on the 14th day after storing because of the chilling damage. The activities of POD of shoots showed a general increase with temperatures increased. Shoots stored at 25°C recorded the highest value of POD activity on the 14th day after storing, which was 6 times higher than that recorded before storage. Shoots stored under low temperatures (3°C, 7°C and 11°C) showed relatively stable activities of POD during the 28 days of storage.6. It can be concluded from the above study results that the optimum temperature for storage and preservation of D. margaritae shoots is 7～11°C.