Removedores de etileno baseados em plataformas nanométricas de sílica e alumina impregnadas com permanganato de potássio para aplicações em póscolheita de frutas e hortaliças

Abstract

Horticultural crops are an important food source for global population. However, crops still show high rates of postharvest losses, due to its high perishability. Ethylene is a plant hormone that regulates aspects such as growth, development, maturation and senescence of plants and their organs. Ethylene production varies between crops and its control can extend the life of fruits and vegetables. Many technologies have been developed in order to control the synthesis and reduce ethylene produced by plants. Oxidation through potassium permanganate (KMnO4) has application in storage, transportation and marketing. Typically, KMnO4 is impregnated in porous platforms displaying high specific surface are, which are aimed at removing ethylene within packaging. Ethylene can be oxidized by KMnO4, which subproducts (after subsequent oxidation), can be converted into water (H2O) and carbon dioxide (CO2). The use of platforms based on mesoporous nanoparticles (with diameters of 5-110 nm) impregnated with KMnO4 allows ethylene oxidation to be carried out more efficiently, once it increases the contact surface area. In this context, this study aimed at developing ethylene absorbers based on nanometric platforms (nanosilica and nanoalumina), associated with potassium permanganate (KMnO4), to remove ethylene produced during postharvest and use color changes during ethylene oxidation as a colorimetric indicator. The performance of nanometric platforms was compared to conventional silica and alumina. The following KMnO4 concentrations impregnated in the platforms were tested: 0; 2.5; 5 to 10%, which values are, respectively, half, equal and twice the values found in commercial ethylene removers. Since relative humidity is a factor that influences ethylene oxidation by KMnO4, the following UR were tested: 45, 60, 75, and 90%. The platforms impregnated with different KMnO4 concentrations and subjected to several RH in closed system, were exposed to a standardized amount of ethylene produced in the laboratory. After 1h and 24h of exposition, injection aliquots were collected for analysis by gas chromatography. The color was measured before placing samples in the closed system and after 24 hours. The silica nanoparticles, synthesized silica and alumina showed superior performance for ethylene absorption, especially when aliquots removal was evaluated in 1h. Among the tested nanoparticles, alumina nanoparticles showed to be the most effective, being able to completely remove the ethylene after 1h, under a greater variety of RH conditions and KMnO4 concentrations. The most suitable combinations, in accordance with the highest color difference and high ethylene absorption performance were synthesized nano-silica + 10% KMnO4 and nano-alumina + 10 % KMnO4 for RH = 45%; nanosilica + 10% KMnO4 and nano-alumina + 10% KMnO4 for RH= 60%; nano-silica + 10% of KMnO4, nano-alumina + 5% KMnO4 and nano-alumina + 10% KMnO4 for RH= 75 and 90%.