تاثير پوشش خوراكي ژل آلوئه‌ ورا بر تركيبات زيست‌ فعال گوجه‌ فرنگي گيلاسي حين نگهداري در دماهاي مختلف

Effect of Aloe vera gel edible coating on bioactive compounds of cherry tomato during storage at different temperatures

در اين پژوهش با توجه به لزوم حفظ ويژگي‌هاي كيفي محصولات كشاورزي در مرحله پس از برداشت و افزايش زمان ماندگاري آنها تاثير پوشش خوراكي ژل آلوئه‌ورا (صفر، 25، 50، 75 و 100 درصد حجمي/ حجمي) و دماي نگهداري (5، 12 و 25 درجه سلسيوس) بر تغييرات برخي از تركيبات زيست‌فعال گوجه‌فرنگي‌هاي گيلاسي حين دوره نگهداري مورد بررسي قرار گرفت. بدين منظور گوجه‌فرنگي‌هاي گيلاسي با غلظت‌هاي مختلف از ژل آلوئه‌ورا به‌روش غوطه‌وري پوشش‌دار شدند و پس از بسته‌بندي به مدت 24 روز در دماهاي مختلف نگهداري شدند. تجزيه و تحليل آماري نشان داد غلظت ژل آلوئه‌ورا، دما و زمان نگهداري تاثير معني‌داري بر روند تغييرات تركيبات زيست‌فعال داشتند (0/05p<) هرچند اين تفاوت بين سطح 75 و 100 درصد غلظت ژل آلوئه‌ورا معني‌داري نبود (05/0

Introduction: Tomatoes are versatile climacteric fruit consumed as raw or processed form. Tomatoes are rich in essential amino acids, monounsaturated fatty acids, minerals and bioactive compounds such as tocopherols, lycopene, ascorbic acid and flavonoids. Unfortunately, climacteric fruits have relatively shorter postharvest life due to ethylene production and high rates of respiration and transpiration. Controlling the atmospheric gas composition, temperature and humidity of the storage room could extend the postharvest shelf life of tomatoes. Alternatively, the postharvest shelf life of tomatoes could be extended through using of the edible coatings. The edible coating consists of a thin layer of the edible material such as proteins, polysaccharides and lipids that can act as a water vapor, gas and solute barrier through creating a semi-permeable membrane around the fruit. The edible coating could prolong the postharvest shelf life and maintain quality of fruits by minimizing respiration rate, water loss and oxidation process. Furthermore, the increasing human demand to use natural agents has also been encouraged the researchers towards the exploitation of effective natural edible coatings from renewable resources. Polysaccharides-based edible coatings have been used to effectively prolong the postharvest shelf life of some climacteric fruits. Aloe vera gel is a polysaccharide matrix rich in physiologically active substances that successfully applied as edible coating to effectively maintain quality and extend the postharvest life of some climacteric fruits. According to the literature review, there is no evidence on the use of fresh A. vera gel as edible coating in cherry tomatoes. Therefore, the main objective of the current research was to compare the effects of using different concentrations of A. vera gel as edible coating and storage temperature on some bioactive compounds of cherry tomato such as ascorbic acid, lycopene, and total phenolic content as well as free radical scavenging activity during a storage period of 24 days. Materials and Methods: Cherry tomatoes were obtained from a local market in Zanjan, Iran. Cherry tomatoes were selected based on uniform size, without any physical damage or infections. Aloe vera leaves were obtained from a local market in Zanjan, Iran. Cherry tomatoes were coated with different concentrations of A. vera gel (0, 25, 50, 75 and 100% v/v) and stored at different temperatures (5, 12, and 25ºC) and 85% RH for 24 days. The ascorbic acid, total phenolic and lycopene contents, as well as antiradical activity of the all-treated samples, were evaluated during the storage. All experiments and analysis were performed in triplicate. Results and Discussion: Statistical analysis showed that A. vera gel concentration, temperature and storage time had a significant effect on the changes in bioactive compounds (p<0.05), although this difference between 75% and 100% A. vera gel concentration was not significant (p<0.05). Based on the results, the amount of ascorbic acid decreased significantly with increasing temperature and storage time, while the application of coating could preserve the ascorbic acid content. On the contrary, lycopene was accumulated during the storage period. During the storage period, the total phenolic content and free radical scavenging activity of cherry tomatoes increased with increasing temperature. Unlike the temperature of 5ºC, which shows a continuous increase, the amount of total phenolic content and free radical scavenging activity of cherry tomatoes began to decrease from the 12th and 8th day of storage period with the increasing of temperature from 12 to 25 ºC. However, with increasing concentration of A. vera gel, the total phenolic content and free radical scavenging activity of cherry tomatoes increased. Conclusion: Based on the findings of the current study, the 75% v/v A. vera gel coating could be a promising natural coating agent for preservation of bioactive compounds of cherry tomatoes during the postharvest life especially at storage temperature of 5 ºC.