Kinetika sušenja smrznutih plodova šlјive

Abstract

Za sušenje se koriste sorte šlјive kombinovanih svojstava, svrstane u grupu srednje kasnih i kasnih sorti, koje sazrevaju od sredine avgusta do sredine septembra. Kako kampanja sušenja traje oko mesec dana, da bi se povećala proizvodnja treba skratiti vreme sušenja, što se postiže različitim predtretmanima, na primer dipovanjem. Druga mogućnost povećanja proizvodnje je produženje sezone sušenja korišćenjem smrznutih plodova, s obzirom da je smrznuto voće dostupno tokom cele godine, a njegov nutritivni sastav se ne razlikuje od svežeg voća. Na taj način smrzavanje se može smatrati predtretmanom u proizvodnji sušene šlјive. Za ispitivanje su korišćene sorte šlјive Instituta za voćarstvo Čačak koje se preporučuju za sušenje (mildora, nada, čačanska rodna i valјevka) i sorta stenlej koja se u Srbiji najčešće koristi za sušenje. Za potrebe eksperimenta plodovi su ubrani probirno u fazi tehnološke zrelosti za preradu sušenjem. Sušenje plodova je obavlјeno u eksperimentalnoj konvektivnoj sušari na temperaturi vazduha 90 °C do postizanja 75% ukupne suve materije. Cilј rada je ispitivanje kinetike sušenja smrznutih plodova u poređenju sa dipovanim (uobičajeni predtretman) i netretiranim plodovima (kontrola). Kod svih ispitivanih sorata netretirani plodovi su se najduže sušili, izuzev kod sorte mildora kod koje se plodovi suše za isto vreme bez obzira na primenjeni predtretman. Smrzavanje se može preporučiti kao predtretman jer sa jedne strane produžava sezonu sušenja, a sa druge strane skraćuje vreme sušenja u odnosu na netretirane plodove, pri čemu se dobija suva šlјiva koja po kvalitetu ne zaostaje za suvom šlјivom dobijenom od svežih plodova. U našim ispitivanjima smrznuti plodovi sorata čačanska rodna, valјevka i stenlej su se osušili za najkraće vreme, dok je kod sorte nada vreme sušenja isto bez obzira da li su plodovi dipovani i smrzavani pre sušenja.

Plum cultivars of combined characteristics, classified into the group of medium late and late cultivars, which ripen from mid-August until mid-September, are used for drying. As drying period lasts about a month, in order to increase production, drying time should be decreased, which is achieved by different pre-treatments, like dipping. Another possibility to increase production is to extend drying season by using frozen fruits, since frozen fruit is available throughout the whole year and its nutritional composition does not differ from fresh fruit. In this regard, freezing can be considered as a pre-treatment in the production of prunes. Plum cultivars of the Fruit Research Institute Čačak intended for drying (ˊMildoraˊ, ˊNadaˊ, ˊČačanska Rodnaˊ and ˊValjevkaˊ) and cv ˊStanleyˊ, commonly used for drying in Serbia, are used for examination. For the purpose of the experiment, fruits were picked selectively at the stage of technological maturity for drying. Drying was performed in an experimental convective drier at air temperature of 90 °C until 75% of total dry matter was reached. The aim of the paper is examination of drying kinetics of the frozen fruits compared to dipped ones (common pre-treatment) and non-treated fruits (control). In all examined cultivars, non-treated fruits were dried the longest, except cv ˊMildoraˊ, which fruits were dried the same time regardless the applied pre-treatment. Freezing can be recommended as a pre-treatment because, on the one side, it extends the drying season, and on the other, decreases drying time compared to non-treated fruits; furthermore the quality of prunes obtained in this way does not lag behined the quality of prunes obtained from fresh plums. In our examinations, frozen fruits of cv ˊČačanska rodnaˊ, ˊValjevkaˊ and ˊStanleyˊ were dried the shortest, while in cv ˊNadaˊ, drying time was the same regardless of whether the fruits were dipped or frozen before drying.