Articles
Effect of freeze drying, oven drying and their combinations on energy conservation and quality of carrot slices
Article number
1387_10
Pages
75 – 82
Language
English
Abstract
An efficient and effective drying method is desired by food processors to preserve fresh carrots.
The present study evaluated the impact of combining oven drying (OD) with freeze-drying (FD) on the drying behaviour, energy requirements, cost implications and physicochemical properties of dried carrots.
The drying conditions were as follows: 36 h of FD, 1 h of OD + 21 h of FD, 2 h of OD + 18 h of FD, 3 h of OD + 15 h of FD, and 9 h of OD. Although the OD had the shortest (9 h) drying time, the dried carrot slices were of poor quality.
Compared to FD only, the combination of OD and FD (OD-FD) reduced the drying time by 39-50%. When compared to OD and OD-FD combinations, FD carrot slices showed significantly (p<0.05) higher β-carotene (0.30-0.72 mg g‑1 DM), lycopene (0.36-0.87 mg g‑1 DM), total phenolic content (7.12-10.36 mg GAE 100 g‑1 DM), and DPPH antioxidant capacity (6.54-9.88 mM AAE 100 g‑1 DM). However, OD-FD significantly decreased energy consumption and cost by 40-56% compared to only FD. Overall, drying at 1 h OD+ 21 h FD produced better β-carotene, total phenolic content and radical scavenging activity retention while reducing energy consumption and costs; therefore, this could be an energy-efficient and time saving drying method to produce good quality and nutrient-rich dried carrot slices.
The present study evaluated the impact of combining oven drying (OD) with freeze-drying (FD) on the drying behaviour, energy requirements, cost implications and physicochemical properties of dried carrots.
The drying conditions were as follows: 36 h of FD, 1 h of OD + 21 h of FD, 2 h of OD + 18 h of FD, 3 h of OD + 15 h of FD, and 9 h of OD. Although the OD had the shortest (9 h) drying time, the dried carrot slices were of poor quality.
Compared to FD only, the combination of OD and FD (OD-FD) reduced the drying time by 39-50%. When compared to OD and OD-FD combinations, FD carrot slices showed significantly (p<0.05) higher β-carotene (0.30-0.72 mg g‑1 DM), lycopene (0.36-0.87 mg g‑1 DM), total phenolic content (7.12-10.36 mg GAE 100 g‑1 DM), and DPPH antioxidant capacity (6.54-9.88 mM AAE 100 g‑1 DM). However, OD-FD significantly decreased energy consumption and cost by 40-56% compared to only FD. Overall, drying at 1 h OD+ 21 h FD produced better β-carotene, total phenolic content and radical scavenging activity retention while reducing energy consumption and costs; therefore, this could be an energy-efficient and time saving drying method to produce good quality and nutrient-rich dried carrot slices.
Publication
Authors
Z.P. Mina, T. Kaseke, T. Fadiji, O.A. Fawole
Keywords
carrot slices, oven drying, freeze drying, bioactive compounds, energy requirements
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