不同真空预冷抽气速率对卷心菜预冷过程及贮藏后品质的影响

Effect of Evacuation Rates on Vacuum Precooling of Iceberg Lettuce and Its Post-storage Quality

摘要:

利用风冷预冷、不同真空预冷抽气速率（降压速率指数Y值分别为A-0.126 min-1；B-0.185 min-1；C-0.315 min-1）等技术对卷心菜进行预冷，预冷后包装并放置于5±2 ℃冷库贮藏。通过测定其过程以及贮藏过程中的相关指标来评价不同预冷方式对卷心菜的影响。结果表明，无论何种抽气速率预冷都要快于风冷，但C组(65 min)与B组（70 min）预冷时间相当，且差异性不显著(P>0.05)。同一真空抽气速率对卷心菜不同部位的降温几乎是同时的。贮藏6 d后，B较其他组而言，其呼吸速率183.9 mg/(kg?h)及顶端CO2（7.2%）含量要明显低于A、C组，而维生素含量C（46 mg/kg）及顶端O2（2.1%）则相反，且差异性均显著（p<0.05）。综上所述，0.185 min-1的抽气速率更适合于卷心菜的预冷。

Abstract:

The techniques of slow air precooling and vacuum precooling with different evacuation rates (pressure reduction rates at A-0.126 min-1, B-0.185 min-1, and C-0.315 min-1) were applied to precool iceberg lettuce, and all samples were packaged after precooling and stored in a cold room (5 ± 2 ℃). The effects of different precooling methods on iceberg lettuce were evaluated by measuring related indices for precooling and storage processes. The experimental results showed that vacuum precooling at any evacuation rate was more effective in removing heat than in slow air cooling. However, the precooling times of groups B (65 min) and C (70 min) were equivalent, showing no significant difference (p > 0.05). Nearly the same amount of time was required to remove the heat in different parts of the iceberg lettuce when the evacuation rate was the same. After six days of storage, group B showed a significantly lower respiration rate 183.9 mg/(kg?h) and CO2 concentration (7.2%), and significantly higher vitamin C (46 mg/kg) and O2 (2.1%) concentrations at the top of the packaging bag than groups A and C. All differences were significant (p < 0.05). In conclusion, an evacuation rate of 0.185 min-1 is suitable for precooling of iceberg lettuce.