草莓真空预冷理论分析及实验研究

摘要

为了研究不同预冷压力对草莓真空预冷的影响,本文首先对草莓真空预冷建立了数学模型并进行了理论分析,得出草莓表面水蒸气扩散量与其表面温度的平方根呈正比,与舱内压力呈反比的结论.同时,分别对草莓在0.5、0.8、1.0 kPa的预冷压力下进行真空预冷实验.实验结果表明:舱内温度变化与预冷压力无关,不同预冷压力下的相对湿度变化趋势相同;不同预冷压力对草莓的冷却速率、失水率以及预冷之后草莓的呼吸强度影响较大,预冷压力越低,冷却速率越高,失水率越低,预冷之后的呼吸强度越弱,预冷压力为0.5 kPa时,其冷却速率为2.36℃/(kg·h),失水率为1.67％,呼吸强度为12 mg CO2/(kg·h);并且有预冷压力越低,同一颗草莓不同位置处(草莓表面、草莓1/4处、草莓中心)的温降差异越大;草莓可溶性固形物含量不受预冷压力的影响.%In order to study the effect of different pre-cooling pressure on vacuum pre-cooling of Strawberry,the mathematic model of strawberry vacuum pre-cooling was established firstly and the theoretical analysis was carried out.It was concluded that the water vapor diffusion of strawberry surface was proportional to the square root of surface temperature and was inversely proportional to the pressure in the cabin.Then,the vacuum pre-cooling experiment was carried out on the strawberries at 0.5,0.8 and 1.0 kPa respectively.The experimental results showed that the variation of cabin temperature had no concern with the pre-cooling pressure,and under different pre-cooling pressure,the relative humidity changed in the same trend.The lower the pre-cooling pressure,the higher the cooling rate and the lower the rate of water loss,the weaker the respirtion intensity after pre-cooling,when the pre-cooling pressure was 0.5 kPa,the cooling rate was 2.36 ℃/(kg· h),the rate of water loss was 1.67％,and the respiration rate was 12 mg CO2/(kg·h),and the lower the pre-cooling pressure,the greater the difference in temperature drop of the same strawberry at different positions (strawberry surface,strawberry 1/4,strawberry Center);the soluble solids content of strawberry was not affected by the pre-cooling pressure.