Combined effect of vacuum and different freezing methods on the quality parameters of cherry tomato (Lycopersicon esculentum var. Cerasiforme)

Freezing has been a convenient technique to maintain the shelf stable properties of tomato fruits and to permit the transportation of the products to remote markets. This study evaluated the effects of four different freezing methods on the quality of cherry tomatoes (Lycopersicon esculentum var. Cerasiforme). Fresh, whole cherry tomatoes were frozen using multistage freezing (I), vacuum pre-treatment + individual quick frozen (IQF) (II), vacuum pre-treatment + static freezing (III), and vacuum pre-treatment + multistage freezing (IV) methods, and afterward stored in polyethylene terephthalate/polyethylene terephthalate/polyethylene (PET/PET/PE) bags at -20 °C and analyzed during 5 months of storage. The percentage of skin cracking, ion leakage, pectolytic enzyme activities, colour values, and lycopene content as well as the total dry matter content and pH values of the cherry tomatoes were significantly affected by both the freezing techniques and storage period. The highest skin cracking and ion leakage and also the highest lycopene retention were found in the vacuum pre-treatment + IQF treated samples. The vacuum pre-treatment + multistage freezing resulted in the lowest skin cracking especially in the early stages of storage. The ion leakage values displayed negative correlations with colour values and lycopene contents. However, the enzyme activities exhibited significant positive correlations with both the colour values and lycopene contents. The lack of correlation between the skin cracking and enzyme activities suggest that the cracking problem is not mainly caused by pectolytic enzyme activities.