多糖类保鲜材料的结晶性能及其对荔枝常温贮藏的影响研究

为了研究用于荔枝涂膜保鲜的多糖类高分子材料的结构及其结晶度在荔枝常温贮藏过程中的变化规律。自制涂膜保鲜材料，用X-射线衍射仪对涂膜保鲜材料进行衍射实验，测定涂膜保鲜材料的结晶性能，选择结晶度最小的涂膜保鲜材料进行荔枝静态保鲜和动态保鲜实验，静态保鲜；经过保鲜处理后的荔枝鲜果装箱，放在实验室贮存；动态保鲜，模拟商品的实际贮运条件，用普通货车运输，车箱温度35-45℃，到达目的地卸车入库贮藏；两种实验的贮藏温度26-36℃，平均湿度约82.5%。结果表明，涂膜保鲜材料的分子量越小，浓度越大，贮藏时间越长，结晶度就越大，乙酰化能降低材料的结晶度，取代度越高，结晶度越小，贮藏过程中涂膜保鲜材料结晶度增大，导致膜破裂，是引起荔枝果皮褐变。影响涂膜保鲜效果的主要原因之一。静态保鲜期可达10-15d，动态保鲜期可达7-10d，好果率均达到85%以上。

The Effect of Pol ysaccharide-based Material Crystallization on the Postharvest Life of Litchi at Normal Temperatures

To probe into the change of the coating material of polyaccharose in structure and crystallization in litchi storage at normal temperatures, a kind of coating material was produced and examined by X-ray diffractometer. The material in smallest crystallizing degree was used for litchi fresh keeping in static and transport conditions. In the static condition, the fruits of litchi were treated and put in containers in lab. In the transport conditions, the fruits of litchi were treated the same as the static and put in truck at 35 - 45 C inside the truck for transportation; in the destination, the litchi were put in store house which kept at 26-36 C , 82. 5% of average humidity. It is found that crystallizing degree of the coating material increases with decreasing of molecule weight of the coating material and increasing of thickness of the coating material and storage time of litchi. The acetylation of polyaccharose could decrease crystallization of coating membrane, especially at high substitution. The increase of crystallization of the coating material caused cracking of coating membrane, leading to pericarp browning of litchi, which is one of the key causation of fresh keeping failure. The storage time of litchi fresh keeping are 10-15 days at static condition and 7-10 days at transport conditions, with over 85% fine fruit rate.