Theoretical analysis and experimental study on strawberry vacuum pre-cooling

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.