Mass Transfer and Textural Changes during Processing of Apples by Combined Methods

Mass transfer and textural changes of ‘Red Delicious’ apple slices and cylinders during osmotic adjustment of aw by the combined method approach were studied at 30, 40 and 50°C. Mass transfer of water and sugar in the treated apple followed typical log-normal behavior with most changes occurring during early stages of the process. The changes followed Crank's equation for diffusion. A negative correlation between apple texture and sugar diffusion was observed. Softening, as well as mass transfer changes, occurred at early stages of osmotic treatment. The texture changes were most pronounced at the edges of the apple tissue where the sugar had penetrated. Softening and sugar uptake were more pronounced when apples were acidified. Apples became firm within 2 hr of the process, when the external layer of the apple cylinders penetrated by sugar was trimmed. Calcium chloride beyond 0.30% minimized tissue softening, but the typical crispy structure of the fresh apple was not restored.