Abstract
ABSTRACT After harvest, onion bulbs are submitted to curing, whose objective is to provide loss of moisture in leaves and drying of outer layers (peel) of bulbs, reaching attractive external coloration and reduction in the intensity of rottenness. The objective of this study was to use an air treatment unit (ATU) - known as heat pump - as an alternative drying method, and to evaluate drying time and preservation of the chemical and physical characteristics. The experiment was carried out in a complete random design with ten replicates and three treatments, which were the following: T1- (control) natural curing in shed; (2) T2- (aeration with air artificially heated by propane burning); and (3) T3- (aeration with artificially dehydrated and heated air using ATU). Curing completion time, relative water content (RWC) of the skin and inner layers, pulp color and skin coloring, total titratable acidity (TTA), total soluble solids (TSS), visual index of dormancy breaking (VID), and fresh weight loss (FWL) were evaluated in this study. No significant difference (p < 0.05) were found for TTA, TSS, VID, FWL, and pulp color among treatments. It can be concluded that T3 promoted a faster curing (12 hours) of bulbs, which provided bulbs with drier skin and intense yellow color.
Highlights
In Brazil, onion, together with potatoes and tomatoes, are the most economically important vegetable crop, both for volume production and the generated income
The air was heated by propane burning conducted by a 1.5kW axial triphase power fan positioned at the silo entrance, with average drying temperature and air relative humidity of 36 °C and 47.9% respectively
While in T2, curing of the bulbs was completed at 27 hours, with a 12-hour cycle and another 3-hour cycle (15 hours with the equipment on plus 12 hours with equipment off)
Summary
In Brazil, onion, together with potatoes and tomatoes, are the most economically important vegetable crop, both for volume production and the generated income. Curing is one of the main processes that determine the maintenance of the quality, aiming at reducing moisture after harvest, which allows the change of skin color, production of volatile sulfurate compounds that enhance the aroma, reduction in the susceptibility of the bulbs to penetration by microorganisms, which are characteristics that change according to the genotype (Finger & Casali, 2002). It can be carried out naturally or artificially. They are carried to the completion of the curing that is completed in a few weeks (Boeing, 2002)
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