Drying of Vitis vinifera L. cv “Sultanina” in tunnel solar drier

Ege University, Agricultural Faculty, Horticulture Department, İzmir, Turkey

^a Corresponding author: burcak.isci@ege.edu.tr

Abstract

Raisin production and export is an important business in Turkey. In this research V. vinifera L. cv. “Sultanina” was dried in polythene tunnel type rack systems solar drier and in direct sunlight (traditional drying method). The inside temperature of the tunnel has been increased by adding solar panels to the drying tunnel. The cluster of grapes was dipped in four different alkali solution (dipping solution); such as 1%, 2%, 3%, and 5% of sodium hydroxide + 1% olive oil. Each application was two replicates and at each repetition to be 2 kg/m² grapes. After dipping grapes were placed on the rack. Drying process were continued until 14% humidity. In the study drying period of the grapes, drying ratio, % moisture, % total soluble solids content, 100 berry weight, berry surface color (CIE, L, a, b), alcohol-soluble color values were measured.

Drying period of grapes in the solar drying tunnel is faster than direct sunlight. Solar tunnel drying was found to be satisfactory and competitive to traditional drying method. The color of grapes dried in the sun drying tunnel not seen a negative change.

Provision of solar dryers in drying, air distribution and heat conservation is to make a positive impact on the drying process and capacity. The most important advantage of the dried product in the tunnel type solar drier is protected raisins from external environment.

The main factor in the drying process is to obtain minimum energy consumption of the product with the desired quality and reach a maximum speed of drying. The results obtained from this research are used in practice compliance.