1- Biosystems Engineering Department, College of Agriculture, Shiraz University, Shiraz, Iran , h.aziminejadian@shirazu.ac.ir
2- Mechanical Engineering of Biosystems, Faculty of Agricultural, University of Jirof, 78671-61167, Jiroft, Iran
3- Biosystems Engineering Department, College of Agriculture, Tarbiat Modares University, Tehran, Iran
Abstract: (3905 Views)
In the present study, the influence of drying temperature on energy consumption and qualitative characteristics of onion including rehydration capacity, vitamin C content and total phenolic content (TPC) was investigated. Onion slices with 3 mm thickness was dried in a hot air dryer at temperatures 0f 40‒70 °C. Specific energy consumption and energy efficiency were significantly (P < 0.05) improved by increasing temperature and obtained to be in the range of 35.83‒59.33 MJ/kg and 4.01‒6.52%, respectively. Increasing air temperature resulted in significant (p < 0.05) improvement in energy consumption indices. Rehydration capacity in the dried onion samples varied from 4.01% (at drying temperature of 40 °C) to 6.52 (at drying temperature of 70 °C). Vitamin C content in fresh samples was 50.19, and in dried samples varied from 14.92 to 21.38 mg/100 g dry matter. TPC was measured using Foline–Ciocalteu reagent and found that the TPC in fresh onions (389.6 mg GAE/100 dry matter) was significantly (p < 0.05) decreased in the dried samples (212.3‒295.8 mg GAE/100 dry matter). Based on the obtained results, drying of the onions at higher temperatures led to more deterioration in vitamin C content and the TPC.
Article Type:
Original Research |
Subject:
Drying, frying, freezing, osmotic dehydration Received: 2019/12/2 | Accepted: 2020/03/9 | Published: 2020/04/29