EFFECIVENESS OF SOME AROMATIC OILS TREATMENTS ON QUALITY CONSERVATION OF PEPPERMEN FRESH CUT HERB UNDER COLD STORAGE

The effect of lavender, lemongrass and thyme volatile oils as a supplementary cold storage treatments on quality preservation of fresh cut herb of Menthe piperita L. , during storage for 15 days at 5°C and 7°C followed by 5 days at 20°C, as a marketing condition simulation, was evaluated during 2018 and 2019 seasons. Physical properties, chemical constituents, respiration rate and volatile oil contents were recorded. The results illustrated that discarded herb %, weight loss %, and external appearance (scale) were greatly affected by both factors of the study. The great effect in this respect was obtained with storage at 5°C than 7°C and the effect was also continuous during marketing period at 20°C. An evident decrease in discarded herb % and weight loss % were obtained due to the applied treatments, whereas external appearance values were higher with applied treatments than control during cold storage durations and marketing period. Aromatic oils treatments with 0.50% of lavender, lemongrass and thyme oils were effective than 0.25% of the three aromatic oils. However, chemical constituents i.e total chlorophyll, L-ascorbic acid and total phenols of fresh cut herb were scored highly increases by storage at 5°C than at 7°C storage conditions. Furthermore, The richest chemical constituents mentioned above were obtained with 0.50% of the three aromatic oils treatments and with superior for marketing durations for 5 days at 20°C. On contrary, total acidity of fresh cut herb recorded the minimum values with applied treatments than control (except the treatment of 0.25% thyme oil) during all cold storage durations and marketing period. On the reverse , electrolyte leakage and respiration rate values were controlled and minimized with the applied aromatic oils treatments under 5°C or 7°C cold storage conditions and followed by 5 days at 20°C as a marketing period. The decreases of both electrolyte leakage and respiration rate of fresh cut herb either with cold storage or due to the applied treatments are considered a good indicators to increase storage longevity and high quality. Meanwhile, volatile oil was greatly affected by both cold storage conditions and supplementary refrigeration treatments with lavender, lemongrass and thyme aromatic oils. Conclusively , it could be concluded that the peppermint fresh cut herb can be treated with lavender, lemongrass and thyme aromatic oils before storage at 5°C for 15 days , handling and marketing under 20°C to conserve the quality of the herb.