Texture and structure of glucose-infused melon

Abstract

The effect of glucose and calcium infusion on texture characteristics and ultrastructure of melon was studied using an Instron Universal Testing Machine and optical and transmission electron microscopy. Resistance to puncture was significantly greater when treatment was performed under vacuum or when Ca 2+ was present during atmospheric and vacuum glucose infusion. Atmospheric treatment produced a smaller resistance to puncture than the one shown by raw fruit. Processing reduced residual relaxation force and relaxation time, showing, the high internal fracture suffered by the fruit during treatment. There was a good correlation between textural changes detected through instrumental measurement and structural alterations of flesh tissues. Vacuum-treated samples showed cell walls with good optical density and a middle lamella still visible. Atmospheric impregnation caused very much reduced staining and disruption of cell walls as well as rupture of membranes. Addition of Ca 2+ during both infusion procedures resulted in more electron-dense cell walls as compared with those impregnated without Ca 2 + .