Stone fruit drying parameters

Abstract

The paper presents the study results on technical and technological parameters in the process of low-temperature drying of stone fruit (plum and apricot) under both laboratory conditions and in a multi-purpose prototype dryer intended for plant material drying. The experimental investigations comprised flow and thermal measurements, technological and kinetic drying parameters. Major emphasis was on temperature and relative humidity of the drying agent and moisture and temperature of the dried material, as well as the drying rate. According to the results obtained, the preheating period was 2-3 hours depending on the type of the material and the drying regime i.e. on the condition of the drying agent. Maximum plum drying rate was recorded 2 h after the beginning of the process and amounted to about 1.15 kg w/kg d.b.h. In the case of apricot drying, maximum drying rate was approx. 0.45 kgw/kg d.b.h. and was registered only 4 hours after the beginning of the drying process, which differed from the plum drying rate under approximately equal drying regime. In addition, the apricot drying kinetics curve differed in shape from the plum drying kinetics curve. The obtained quality of both dried fruits under low-temperature drying conditions was found to meet standard requirements to a great extent primarily respecting sugar and acid loss and the fact that there was no odor or contamination of the fruit. The results obtained showed that, in addition to the technical designs of the drying system, the fruit drying process was found to be significantly affected by how the process itself the duration of which could be reduced, was being managed.

U radu su prikazani rezultati istraživanja tehničko tehnoloških parametara procesa niskotemperatuskog sušenja plodova koštičavog voća (šljiva i kajsija). Eksperimentalna istraživanja sprovedena na laboratorijskoj instalaciji i na prototipskoj univerzalnoj sušari namenjenoj za sušenje biljnih materijala, obuhvatila su strujnotermička merenja, parametre kinetike procesa i tehnološke parametre sušenja. Posebno su analizirani temperatura i relativna vlažnost agensa sušenja, vlažnost i temperatura materijala za sušenje kao i brzina sušenja. Rezultati pokazuju da period pregrevanja materijala iznosi od 2-3 h, što je uslovljeno vrstom materijala i režimom sušenja tj. stanjem agensa sušenja. Maksimalna brzina sušenja plodova šljive nastaje nakon 2 h i iznosi oko 1,15 kg w/kg s.m.h. Kod sušenja plodova kajsija maksimalna brzina sušenja iznosi približno 0,45 kgw/kg s.m.h. i pojavljuje se tek nakon 4 časa od početka procesa u čemu se razlikuje od brzine sušenje plodova šljive za približno isti režim sušenja. Pored toga, kriva kinetike sušenja kajsija ima drugačiji oblik u odnosu na krivu sušenja šljiva. Ostvaren kvalitet obe vrste osušenih plodova sa navedenim niskotemperaturskim režimima u velikoj meri odgovara standardima pre svega u pogledu gubitka šećera i kiselina, kao i odsustva bilo kakvih mirisa i zagađenosti plodova. Dobijeni rezultati ukazuju da, pored tehničkih rešenja sistema za sušenje, na uspeh procesa značajan uticaj ima i samo vođenje procesa čije se trajanje može redukovati.