Monitoração por termografia infravermelha da qualidade pós-colheita de goiabas armazenadas sob refrigeração

Abstract

This work aimed at evaluating the postharvest quality of guavas stored at different temperatures by using infrared thermography. We conducted three experiments with three different temperatures and one storing time. The first experiment was done with static air in a refrigerator with a constant temperature of 5 °C; the second experiment was conducted in a refrigeration chamber with forced air at a constant temperature of 10 °C; and the third in an air conditioned environment at a constant temperature of 20 °C. The determined analyses were of mass loss, firmness, respiration rate, color, pH, soluble solids, titratable acidity, SS/AT, vitamin C, total and soluble pectin, total sugars, PME and PG. The experiment was conducted in a completely randomized design, disposed in a 2 x 3 factorial arrangement. Through the thermography it was possible to distinguish the injured tissues of those unaffected at temperatures of 5 and 20 ⁰C, however it was not possible to distinguish deep and shallow injuries on the guavas. The temperature variations between the surface of the intact and injured tissues can be quantified, and this difference in temperature is correlated to injury. In the guava stored at 5 ⁰C, the injured tissue presented itself at a lower temperature than the intact tissue; in those stored at 20 ⁰C, the injured tissue presented itself at a higher temperature than the intact tissue; while at the temperature of 10 ⁰C, there was no significant change between the injured and intact tissues. Infrared thermography has potential application in assessing and monitoring the quality and safety profile of guavas stored at different temperatures, since it detects the appearance of injuries, both mechanic and by cold, and fruit senescence. The refrigerated storage at 10 ⁰C was important for maintaining the quality of guavas, while the 5 ⁰C the guavas suffered chilling injury and 20 ⁰C they lost the characteristics acceptable for consumption. The quality parameters evaluated by the physical and chemical analyses confirmed the results observed in the thermographic analysis.