ABSTRACT
Calcium is used to decrease undesirable softening in fresh apples during storage. Calcium is believed to act by two general mechanisms. One involves regulation of cell function, such as changes in cell wall structure and membrane permeability. The other is the interaction of calcium with pectin to form a cross-linked polymer network that increases mechanical strength (Poovaiah, 1986; Glenn and Poovaiah, 1990). Infiltration of calcium into fresh apple tissue and processed apples has been utilized to maintain firmness (Mason, 1976; Johnson, 1979; Sams and Conway, 1984; Abbott et al., 1989; Glenn and Poovaiah, 1990). From ultrastructural studies, infiltrated calcium is shown to bind to cell walls and the middle lamellae where it exerts its major influence on firmness (Glenn and Poovaiah, 1990). The objectives of this study were to relate textural and structural changes induced by the osmotic adjustment of aw and to examine the role of calcium in preventing the softening of apples preserved by combined methods.
