Respiration substrates oxidation kinetics of grape for table use at refrigerated storage with track membranes

Abstract
The article deals with fruit long term storage issue. The goal of the storage is to minimize losses due to pathogens or physiological reasons. It of crucial importance then to maintain a certain temperature as well as an atmosphere composition with lowered level of oxygen and higher level of carbon dioxide. Different polymer or woven membranes are used for storage fresh fruits under modified atmosphere conditions. They have gas-selective and adhesive properties. The authors analyze using new high-tenacity gas selective track-membrane based material. It is used to create an atmosphere with lowered level of oxygen and higher level of carbon dioxide in an enclosed volume by self-regulation of fruit respiration. The changes in mono- and disaccharide content and organic acid content during storage of Sultana and Tayfi pink grape for table use with track membranes with pores of different diameter are analyzed. Constants of pseudo-first order oxidation speed for mono- and disaccharides К1 and organic acids К2 are calculated. The maximum of mono- and disaccharides and organic acids is shown to be preserved in Sultan grape at the temperature of 3±1º С up to 75 days, and in Tayfi pink grape – up to 120 days. For reference samples the storage time equals 45 and 80 days. The advantages of using modified atmosphere created by gas selective composite membrane of (16±2) sм²/kg square S for refrigerated storage of Sultana and Tayfi pink grape for table use are shown. The membrane consists of polyethyleneterephthalate track-membrane base and selective layer from organosilicon block copolymers of 2,2% concentration with pore diameter d = 0,2 mkm.