Compositional and physicochemical changes associated to successive osmodehydration cycles of pineapple (Ananas comosus)

As a technique for obtaining minimally processed fruits, osmotic dehydration (OD) is adequate, and does posses advantages over other drying techniques, yet it seems that some hydrosoluble components may escape into the osmotic solution (OS) during the process. On the other hand, the re-use of the OS in successive OD operations can be a good way of making the process economical and environmentally friendly. In this work, 15 successive cycles of pineapple dehydration were programmed. OD was carried out for 2 h at 30 °C with an OS:fruit rate of 20:1, using a 55 °Brix sucrose solution. In each OD cycle, the fruit was renewed but the OS was re-used without any re-concentration treatment. In each cycle, soluble solids (°Brix), water content (xw), water activity (aw), pH, citric acid (CA), majority minerals (Ca, Mg, K, P and Na) and pectin content were analysed in the pineapple slices and in the OS. Electrical conductivity (EC) and viscosity (μ) of the OS were also analysed. The results obtained allow us to confirm a loss of CA, pectin and studied minerals that ranged between 21 and 59 mg/100 mg of the component present in the fresh fruit. The flow of these components to the OS may be predicted from EC and μ measurements of the OS.