Evaluation of the Impact of Hot Water Treatment On the Sensory Quality of Fresh Tomatoes in Cold Storage

Minimizing the effects of chilling injury during shelf-life is important for maintaining the sensory quality of fresh tomato fruit. Postharvest hot water treatments within certain limits of exposure time and temperature have been shown to increase resistance of tomatoes to chilling injury. Mature-green (MG) and Breaker/Turning (BT) ‘BHN-602’ tomatoes harvested in spring 2009 were submerged in water at 25 (control) or 52°C for 5 minutes. MG fruit were then exposed to 100 µl/L ethylene for 2 days at 20°C to uniformly initiate ripening; any fruit not exhibiting external red color after the ethylene treatment were discarded as immature. The remaining MG and BT fruit were stored at 5, 12.5, or 20°C. After 1 week, tomatoes were transferred from 12.5 and 5°C to 20°C until fully ripe. Ripeness was evaluated by measuring color (CIE a*) on the blossom end of the fruit until a* reached an acceptable value. When selected as fully ripe, fruit firmness, sugars, organic acids, and volatile compounds were measured and a trained panel evaluated sensory quality using 15 descriptors measured on a 16-point scale. Sensory data were analyzed by several methods of multivariate analysis including principal component analysis (PCA) and agglomerative hierarchical clustering (AHC). PCA and AHC showed that tomatoes grouped into three clusters defined by their sensory descriptors. Fruit stored only at 20°C were clustered together regardless of heat treatment and had the highest perceived firmness as shown by the PCA biplot. Fruit harvested at the MG stage were characterized by the sensory quality descriptors ‘overall tomato’, ‘fruity’, ‘sweet’ and ‘salty’, regardless of water treatment temperature and storage temperature. Tomatoes at the BT stage had high scores for ‘mealiness’ and ‘sourness’, except those that were treated with 52°C water and stored at 5°C; those tomatoes had high scores for ‘earthy/musty’ aroma and flavor. When the experiment was repeated in fall 2009, tomatoes stored at 20°C had the highest scores on PC1 with descriptors of ‘tomato’, ‘fruity’, and ‘vine’ aroma and flavor.  BT fruit were characterized as ‘mealy’, and MG fruit were described as ‘sour’, ‘salty’, and ‘earthy’.  However, one group of fruit was positively affected by the treatments as they had positive scores on PC1; these were MG and BT fruit treated with 25 or 52°C water then stored 1 week at 12.5°C, and BT fruit without heat treatment stored at 5°C for 2 weeks.