KINETICS OF DRYING AND QUALITY OF THE APPLE CULTIVARSGRANNY SMITH, IDARED AND JONAGOLD

Apple is nutritionally valuable and present as fresh fruit in humannutrition throughout the year. Also apple is a raw material in food processing,primarily in the production of juices, nectars, refreshing soft drinks, marmalades,jams, compotes, apple cider vinegar and dried fruits. In the last decade on theworld market there is a great interest in dried apple products (commercially calledapple chips). During preservation by drying the technological process aimed at thefinal product of optimal quality is required. The subject of this paper is the kineticsof the apple cv. Granny Smith, cv. Idared and cv. Jonagold drying in laboratorydehydrator for the purpose of pinpointing at which level of humidity the maximumspeed of evaporation is achieved and at which level of humidity apple slices beginto change in colour and geometric shape. Parameters of the drying process were thesame for all three cultivars, 3hrs at air temperature of 70oC and 5hrs at airtemperature of 50o. The amount of evaporated water is expressed in relative andabsolute units of measure. The purpose of this paper is to determine which one ofthe three tested cultivars provides the best properties for drying, i.e. in terms ofoxidation of polyphenolic compounds to find the cultivar which will provide thatthe final product is technologically and organoleptically the most acceptable. Theresults showed that the sample cv. Granny Smith expressed the least oxidation ofpolyphenolic compounds (browning), curved edges and shrivelled apple slices.After that the sample cv. Jonagold followed. The sample cv. Idared showed theworst results. Following the drying kinetics of all three samples, it can beconcluded that the cultivars Granny Smith and Jonagold were achieving the lowermaximum speed of evaporation, unlike the cultivar Idared. The cultivars GrannySmith and Jonagold have attained consistent drying and in this way thetechnological process was finished with a smaller temperature stress for planttissue, resulting in a much better quality of the final product.