Home-Drying Operation Effect on Moisture Content, Electric Energy Consumption, Ascorbic Acid, Total Polyphenol Content, and Color of Sliced "Fuji" Apples

Abstract

A home dehydrator allows obtaining dried apples that are beneficial to human health, but its operations will affect the chemical and organoleptic quality of this fruit. In this study, the effect of the drying temperature and mass load of sliced fresh "Fuji" apples in a home dehydrator was evaluated with regard to moisture content, electric energy consumption, ascorbic acid, total polyphenol content, and color of the dried fruit. Fresh "Fuji" apples were cut to obtain a uniform slice with a thickness of 4 mm and diameter from 60 to 75 mm. A home dehydrator was operated at 50 and 70°C (nominal temperatures), with a total sliced apple load of 250 and 500 g, uniformly distributed in five trays. Drying was carried out for 7 hours, and every hour, the trays were rotated, changing their position from the top to the bottom. Only the middle tray was always kept in the same position. As result, the level of nominal temperature (50/70°C) was not reached for any of the trays, regardless of the mass load (250/500 g) in the home dehydrator. The temperature average for fruits dried in trays of the home dehydrator that were rotated (top and bottom) and kept in the same position (middle) did not differ (p > 0.05) among them. At the end of drying, the apple treatment at 50°C/250 g, 50°C/500 g, 70°C/250 g, and 70°C/500 g reached 23.1, 26.2, 4.3, and 4.5% (w.b.), respectively. The drying conditions at nominal 50°C favored the quality of the dried sliced apples with regard to ascorbic acid and total polyphenol content; however, the treatment at nominal 70°C produced less variation in color with respect to the fresh fruit. The home dehydrator allowed obtaining sliced dried "Fuji" apples that adequately preserve the ascorbic acid, total polyphenol, and color with respect to the fresh fruit.

Figure 1

Temperature evolution inside the middle tray of home dehydrator during drying of sliced “Fuji” apples.

Figure 2

Temperature evolution inside the top tray of home dehydrator at the beginning of drying of sliced “Fuji” apples and their sequential rotation at the bottom position.

Figure 3

Temperature evolution inside the bottom tray of home dehydrator at the beginning of drying of sliced “Fuji” apples and their sequential rotation at the top position.

Figure 4

Evolution of moisture content (w.b.) of sliced “Fuji” apples (middle tray) during drying in home dehydrator.

Figure 5

Evolution of electric energy consumption with respect to moisture content (w.b.) of sliced “Fuji” apples (middle tray) during drying in home dehydrator.