OSMOTIC DEHYDRATION OF POMEGRANATE SEEDS (PUNICA GRANATUM L.): EFFECT OF FREEZING PRE‐TREATMENT

Abstract

ABSTRACTThe osmotic dehydration of pomegranate seeds was compared using fresh and frozen seeds. The process was carried out at 50C in a 55°Brix solution of sucrose. Freezing pomegranate seeds before osmotic dehydration involved an increase of effective diffusivity and a reduction in dehydration time. The most significant changes of water loss (WL) (46 g/100 g of fresh seeds [FS]) and solids gain (SG) (7 g/100 g of FS) took place during the first 20 min for frozen seeds. After this period, seeds WL and SG ranged on average close to 43 and 8 g/100 g of FS, respectively. Osmotic dehydration was slower starting from fresh fruits but led to a higher rate of WL (62 g/100 g of FS) at the end of the process. Both scanning electron microscopy and texture analysis showed a destruction of cell structure and seed texture during the pretreatment (freezing). The same techniques also revealed a texture/structure modification induced by the osmotic dehydration process.PRACTICAL APPLICATIONSIn Tunisia, the research of addition value to pomegranate seeds is very limited and presents a traditional feature such as jam preparation or direct consummation of fruit during the crop season (between September and December). However, other perspectives of transformation and exploitation of the pomegranate seeds should be undertaken to give an added value to this typical fruit. Osmotic dehydration can be an alternative process to increase the conservation time of fruit and to give a new osmodehydrated fruit that can be included in some food formulation such as ice cream, cereals, dairy, confectionery and bakery products.