Abstract:
The effect of methyl jasmonate (MJ) and modified atmosphere packaging (MAP) on the reduction of chilling injury and the extension of shelf-life of mature green tomato (Lycopersicon esculentum Mill.) were investigated. This study was separated into 3 parts including (1) determination of the optimum concentration of MJ (2) determination of the optimum modified atmospheric condition and (3) utilization of the optimum MJ combined with the optimum MAP to reduce chilling injury and extend shelf-life of tomato. Firmness, total soluble solid, pH, titratable acidity, weight loss, color and sensory evaluation (degree of chilling injury, defect, color and overal acceptance) were used to indicate the qualities of tomato and were monitored throughout the storage in all experiments. The optimum concentration of MJ was determined by vaporizing tomatoes with 10[superscript -4] M (MJ 10[superscript -4] M) and 10[superscript -5] M (MJ 10[superscript -5] M) before packaged in 8x11 in[superscript 2] FRESHPAC[superscritp TM] bags under atmospheric condition and stored at 5 ํC and 50% relative humidity (RH). Tomatoes without MJ treat were used as control. MJ 10[superscript -4] M showed significantly higher (p [is less than or equal to] 0.05) qualities and less (p [is less than or equal to] 0.05) chilling injury scores than MJ 10[superscript -5] M and control. Control, MJ 10[superscript -5] M and MJ 10[superscript -4] M could be stored for about 4, 4 and 6 weeks, respectively. To determine the optimum MAP, tomatoes were packaged under atmospheric air (control), 2.5%O[subscript 2]/2.5%CO[subscript 2]/95%N[subscript 2] (MAP1), 5%O[subscript 2]/5%CO[subscript 2]90%N[subscript 2] (MAP2), 7.5%O[subscript 2]/0%CO[subscript 2]/92.5%N[subscript 2] (MAP3) and 2%O[subscript 2]/80%CO[subscript 2]/18%N[subscript 2] (MAP4) and stored at 5 ํC and 50% RH. The qualities of tomatoes in MAP2 were significantly better (p [is less than or equal to] 0.05) and less (p [is less than or equal to] 0.05) chilling injury scores than other treatments. The results showed that tomatoes in MAP1, MAP3, MAP4 and control had shelf-life of about 4 weeks, while MAP2 can be kept for up to 6 weeks. In the final experiment, optimum MJ combined with MAP2, MJ+MAP, was used to reduce chilling injury and extend shelf-life of tomatoes and was compared with heat treatment (HT), control and no packed tomato (no pack). Tomatoes in MJ+MAP showed better qualities and less (p [is less than or equal to] 0.05) chilling injury scores than those in HT, control and no pack. Moreover, MJ+MAP could maintain ascorbic acid and lycopene content as well as reduce (p [is less than or equal to] 0.05) ethylene production better than other treatments. Control, HT and no pack could be stored for about 4, 6 and less than 4 weeks, respectively, while MJ+MAP could be stored up to 8 weeks.