Perfil antioxidante de tomates submetidos a métodos de conservação pós-colheita

Abstract

Post-harvest conservation methods can minimize the oxidative stress of fruits to guarantee the maintenance of their antioxidant status. Some conservation methods may even raise the nutritional and antioxidant profile through the accumulation of phytochemicals, such as carotenoids and ascorbic acid, by activating the defense system of the plant organ. The objective of this work was to evaluate the antioxidant profile of tomatoes subjected to storage in a modified atmosphere and to thermal shock. Two experimental tests were carried out using two methods of post-harvest conservation: tomatoes stored in a modified atmosphere and tomatoes subjected to heat shock treatment with hot water (45 °C ±2; 10 min). In the first trial, 'BRS Nagai' tomato fruits were used, and in the second trial 'Sweet Grape' tomatoes were used. Both trials consisted of 5 replicates per treatment. β-carotene, ascorbic acid, total phenolic compounds, antioxidant activity (DPPH, ABTS and FRAP), respiration rate and loss of fresh weight were evaluated every 7 days in the first trial, and every 3 days in the second trial. The data were subjected to statistical analysis, except for data from analyzes performed on liquid chromatography, which were presented by average values. The data were also submitted to Pearson's correlation analysis in order to exclude the relationship between the bioactive compounds analyzed and the methods of analysis of antioxidant activity. The results showed that in the test with modified atmosphere there was retention of the content of β-carotene in the pulp and an increase of β-carotene in the skin of 'BRS Nagai' tomatoes during storage. There was a decrease in ascorbic acid, total phenolic compounds and antioxidant activity of the pulp and skin of tomatoes. The appearance of pathogens in tomatoes during storage in a modified atmosphere at room temperature contributed to their greater stress, with a consequent increase in respiratory rate. The thermal shock, in turn, promoted an increase in the β-carotene content and the antioxidant DPPH activity in the peel, in addition, it promoted retention of the antioxidant activity ABTS and FRAP in the pulp of 'Sweet Grape' tomatoes. The moderate stress caused by heat shock was associated with an increase in the content of β-carotene, as well as other compounds were positively affected by heat treatment. There was an increase in the respiration rate and loss of fresh weight of the treated tomatoes, however, wilting or dehydration symptoms were not observed, showing good appearance until the last day of storage. The results of the correlation analysis indicated that ascorbic acid was associated with antioxidant DPPH activity, while β-carotene and total phenolic compounds from the peel of tomatoes in both trials were associated with ABTS antioxidant activity. In view of the results presented, the thermal shock treatment provided better retention and increase in the antioxidant properties of tomatoes, compared to the treatment with modified atmosphere, demonstrating to be an effective treatment in maintaining the antioxidant profile of tomatoes.