荔枝不同预冷方式降温特性研究

Cooling characteristics of different precooling methods for litchi

【目的】研究荔枝不同预冷方式的降温特性.【方法】建立差压预冷试验箱,以"淮枝"为材料,采用冰水(L1)、冷库(L2)、差压(L3)以及高湿差压(L4)进行预冷试验.【结果和结论】L1、L2、L3、L4分别需耗时35、55、64和345min将平均果温降至目标温度(5℃).L1不同位置降温无显著差异.L2分别用195、258和228 min将左右侧和上层果温降至5℃,345 min后中下层和中间位置果温仍分别高达5.37、6.16和7.37℃;左右与中间处降温差异显著.L3分别用39、52、42 min将左右侧和上层果温降至5℃,55 min后中下层和中间位置果温仍分别高达6.03、5.67和9.03℃,上层与中下层果温差异显著;L4分别用39、41 min将左侧和上层果温降至5℃,64 min后中下层和中右位置果温仍分别高达5.86、8.83、7.87和6.63℃,左侧和中间处降温差异显著.L1预冷效率高、果温均匀性好,是荔枝较适合的预冷方式.

【Objective 】To study the cooling characteristics of different precooling methods for litchi.【Method】A pressure-difference precooling test chamber was established. Four precooling methods,including ice water( L1),cold storage( L2),pressure-difference( L3) and forced-air pressure-difference with high humidity( L4),were adopted for 'Huaizhi ' litchi. 【Result and conclusion 】 The results showed that L1,L2,L3 and L4 spent 35,55,64 and 345 min respectively to precool the litchi down to the target temperature( 5 ℃). The cooling procedure of litchi fruit at different positions for L1 performed no significant difference. L2 took 195,258 and 228 min to precool litchi at left and right positions and top layer respectively. However,the fruit temperature at middle and bottom layer and middle position were still up to 5. 37,6. 16 and 7. 37 ℃ respectively after 345 min precooling; and the cooling procedure of litchi fruit showed significant differences between the left,right position and its middle position. L3 took 39,52,42 min to precool litchi at the left and right positions and top layer respectively. However,the fruit temperature at middle and bottom layers and middle position were still up to 6. 03,5. 67 and9. 03 ℃ respectively after 55 min precooling. The cooling procedure of litchi fruit showed significant difference among the top layer,left position and its middle and bottom layers. L4 spent 39 and 41 min to precool litchi at the left position and top layer respectively. However,the fruit temperature at the middleand bottom layers,middle and right positions were still respectively up to 5. 86,8. 83,7. 87 and 6. 63 ℃after 64 min precooling. The cooling procedure of litchi fruit showed a significant difference between the left position and its middle position. L1 has high cooling efficiency and good fruit temperature uniformity,which is suitable for cooling litchi.