Osmotic-treatment-induced cell death and osmotic processing kinetics of apples with characterised raw material properties

Three apple varieties cultivated in southern Sweden namely Jonagold, Kim and Mutsu were subjected to osmotic treatment at 5, 20 and 40 degreesC with a 50% sucrose solution. The evaluation of cell viability after osmotic processing, was carried out in Granny Smith apples from Argentina. The processing conditions were 50% sucrose solution at 20 degreesC and the viability assay used was based on the reduction of 2,3,5-triphenyltetrazolium chloride (TTC). The experimental samples were separated into inner (close to the apple core) and outer (close to the skin) specimens, due to the existence of pronounced structural differences between them. The kinetics revealed that for each apple variety and at each process temperature, samples of the outer structure exhibited higher water loss and lower solids gain than those of the inner structure. Overall, the Jonagold and Kim apples exhibited similarly high water loss, while Mutsu showed a lower loss. Jonagold absorbed the lowest amount of solids with Kim rating second and Mutsu apples showing the highest solids gain. The cell viability assay on the experimental samples revealed the first layer of cell in a depth 1-2 mm from the surface to die as a result of the severe osmotic shock. (C) 2003 Elsevier Ltd. All rights reserved.