Qualidade pós-colheita de Longans submetidas ao tratamento hidrotérmico e de desidratação, embaladas e armazenadas sob refrigeração

Abstract

The longan (Dimocarpus longan Lour) is a major crop, grown commercially in tropical and subtropical climate zones. Due to the lack of information related to postharvest conservation, it is necessary to carry out studies that help to improve the conservation conditions of the fruit, seeking to increase shelf life and maintenance of organoleptic properties. Therefore, this work aimed to study longan’s post-harvest quality submitted to different drying temperatures and hydrothermal treatment, in addition to the effect related to the presence and absence of packaging in refrigerated environment, verifying the quality variables: physical, physical-chemical and bioactive. After the harvest, the fruits were transported from Fazenda Coqueiro, located in Santa Rita do Passa Quatro – SP, to the Laboratory of Drying and Storage of Vegetable Products, Universidade Estadual de Goiás - Campus of Exact and Technological Sciences - Henrique Santillo, in Anapolis - GO. The project was divided into two experiments, both in a completely randomized design with four replications. In the first experiment, with a 6x2x6 factorial scheme, the fruits were submitted to six temperatures of hydrothermal treatment (25 (control), 45, 47, 49, 51 and 53 °C); packed in low density polyethylene packaging - LDPE or without packaging (control); and evaluated every three days for a total of 6 days of analysis (0, 3, 6, 9, 12 and 15 days). The second experiment used a factorial scheme of 5x9, five dehydration temperatures (60, 65, 70, 75 and 80ºC), lasting 12 hours each, and nine days of analysis, which were performed every three days (0, 3, 6, 9, 12, 15, 18, 21 and 24 days) and stored in LDPE packaging. In both experiments, after application of the treatments, the fruits were stored and kept in a BOD incubator at 75+5% U.R and storage temperature of 4+2ºC. The following analysis were studied during storage: mass loss, firmness (1st experiment), soluble welds (SS), titratable acidity (AT), maturation index (IM), coloring (L *, ° Hue, Chroma and Darkening Index), hydrogen potential (pH), pulp / peel and pulp / seed ratio (1st experiment), ascorbic acid (vitamin C) (1st experiment), antioxidant activity (1st experiment) and extractable polyphenols (1st experiment). The data obtained with the respective tests were subjected to analyze of variance (P≤0.05) and, when significant, the means were compared by Scott Knott's test at 5% probability for the packaging factor and regression for the other factors. It was possible to conclude that the fruits that were submitted in different hydrothermal treatment temperatures have obtained positive results, with emphasis on the treatment at 45ºC, which provides greater conservation in the longan’s physicochemical characteristics, and 53ºC, which generates improvements in longan’s bioactive characteristics, due to an increase in the antioxidant activity and polyphenols parameters. While longans that were packaged in LDPE it was observed a greater conservation of desirable qualities. Regarding the dehydration experiment, the temperatures that stood out the most were 80ºC, due to the higher results in all parameters, and 75ºC, which furthermore have obtained positive results for all tests, maintaining the fruit’s quality during storage, in addition to extending the longan’s useful life. Both experiments were able to conserve the fruits for their respective entire storage period.