The kinetics of the apple cv. Granny Smith drying in laboratory conditions

Abstract

In the last decade on the world market there is a great interest in dried apple products (publicity-called apple chips). The subject of this paper is the kinetics of the apple cv Granny Smith drying in laboratory dehydrator with the idea of pinpointing at which level of humidity comes to achieving a maximum speed of evaporation and at which level of humidity apple slices are beginning to change in color and geometric shape. The experiment included two temperature regimes of drying, batch process (constant air temperature of 70°C for a period of 8h) and simulated continual process (the air temperature of 70°C for a period of 3 h and the air temperature of 50°C for a period of 5 h). The amount of evaporated water is expressed in relative and absolute units of measure. The purpose of this paper is to optimize the technological process of drying apple slices and in terms of oxidation of polyphenolic compounds to find an adequate temperature treatment which will provide that the final product contains no additives and to be technologically and organoleptically acceptable. The results showed that in simulated continual process of drying the lower maximum speed of drying is achieved, drying is more evenly and in this way the technological process is finished with a smaller temperature stress for plant tissue, resulting in a much better quality of the final product.

Poslednjih decenija na svetskom tržištu postoji veliko interesovanje za sušene proizvode od jabuke (marketinški nazvane čips od jabuke). U ovom radu je izučavana kinetika sušenja jabuke sorte Granny Smith u laboratorijskom dehidratoru sa idejom da se uoči pri kojim sadržajima vlage dolazi do postizanja maksimalne brzine isparavanja i pri kojoj vlažnosti kolutovi jabuke počinju da menjaju boju i geometrijski oblik. Primenjena su dva temperaturna režima sušenja: šaržni (konstantna temperatura vazduha od 70 °C u trajanju od 8h) i simulirani kontinualni (temperatura vazduha od 70 °C u trajanju od 3h i temperatura vazduha od 50°C u trajanju od 5h). Količina isparene vode je izražena u relativnim i apsolutnim jedinicama mere. Cilj ovog rada je da se optimizuje tehnološki postupak sušenja kolutova jabuke tako da se, sa aspekta oksidacije polifenolnih jedinjenja, pronađe adekvatni temperaturni režim koji omogućava da gotov proizvod ne sadrži aditive, a da je tehnološki i organoleptički prihvatljiv. Rezultati su pokazali da se pri simuliranom kontinuelnom načinu sušenja postiže manja maksimalna brzina, sušenje je ravnomernije i da se na taj način tehnološki postupak vrši sa manjim temperaturnim stresom za biljno tkivo što rezultira mnogo boljim kvalitetom gotovog proizvoda.