Agriculturae Conspectus Scientificus, Vol 63, No 3 (1998)

Influence of Conective Drying on the Properties of Idared and Božićnica Apples, Cut Into Slices


Pages: 121-127


This paper deals with the research that was carried out into the influence of convective drying on the properties of slices of Božičnica and Idared apples. The average sample of fruits weighing from 107.59 to 151.71 grammes produced 17.49 to 21.36% of epidermis, and 13.94 to 17.01% of seed cases, whereas the exploitability of fruits was 49.96 to 54.59%, with significant differences in Idared apples.
Prior to drying, the fruits were cut into 6 to 8 mm-thick slices which were then treated with an antioxidant and immersed into a 0.1% solution of L-ascorbic acid. Next, they were exposed to convective drying which was done in two stages and at different temperatures. During the first stage of drying, the air temperature varying from 80.37 to 83.90 0 C heated the slices to 45.28 0 C - 46.18 0 C. The average drying air speed was 1.98 m/s, while the drying time was from 58 to 73 minutes for the 229.6 - 275.0 gramme samples. In the course of the second stage of drying, the air temperature from 65.25 to 70.90 0 C heated the slices to 40.06 0 C - 42.15 0 C, with the air speed of 1.85 m/s and the drying time of 92 -114 minutes.
Fresh slices contain 12.36 - 15.60% of dry matter which increases after drying to 82.59 - 84.61%. The drying curves of the samples under research were modelled by the following equation of linear regression, showing no significant differences:
y = 88.0627 + (- 0.4281x * min)
where determination coefficient
r = - 0.9812; R2 = 0.9628 and sx = 4.33.
The properties of fresh and dried slices were worked out by means of chemical analyses, organoleptic evaluations and rehydration ratios. Testing of differences in dry matter content and saccharose among fresh and dried slices showed some statistically significant variations, whereas testing of differences in the amount of L - ascorbic acid, pH values and overall acidity among fresh and dried samples resulted in no statistically significant variations. Rehydration ratio, one of the most important indicators of the quality of drying, varied from 4.03 to 4.90 and showed no significant differences. Testing of differences in organoleptic colour values among dried slices showed some statistically significant variations in Božičnica apples.


convection; drying; Božičnica ; Idared; slices

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