Energy analysis and quality characteristics of flaxseed oil by using an infrared rotary dryer

Abstract

An infrared (IR) rotary dryer was designed and fabricated to sterilize flaxseeds under different experimental treatments. The investigations were conducted under varying IR intensities (882, 964, 1050, and 1140 W/m2) and exposure times (6, 9, 12, and 15 min). Data analysis showed the minimum amount of specific energy consumed at 882 W/m2 and 6 min for the studied varieties Sakha 3 and Sakha 6. The highest thermal efficiency belonged to the highest radiation intensity and the lowest exposure time, with values of 77.26 % and 86.17 % for Sakha 3 and Sakha 6, respectively. Different IR intensities caused an increase in oil yield (OY), acid value (AV), and peroxide value (PV). For example, 1050 W/m2 for 15 min showed the highest OY for Sakha 3 (37.37 %), whereas 964 and 1050 W/m2 for 12 min reported the highest activity for Sakha 6 (43.20 and 43.43 %, respectively); 1140 W/m2 was the intensity that recorded the highest content of AV (range of 2.67–3.93 mg KOH/g for Sakha 3 and 3.19–4.22 mg KOH/g for Sakha 6) and PV (range of 4.05–6.91 meq. O2/kg for Sakha 3 and 5.21–5.92 meq. O2/kg for Sakha 6). Moreover, increasing IR intensity caused an increase in total phenolic content. The maximum amount was obtained at 1140 W/m2 for 12 min (153.27 and 154.59 mg GAE/100 g sample for Sakha 3 and 6, respectively) without significant changes at 1050 W/m2 and 12 min. For radical scavenging activity, 1050 W/m2 at 9, 12, and 15 min represented the highest activity for Sakha 3 (range of 30.27%–32.64 %) and Sakha 6 (range of 36.58%–37.37 %). Thus, IR pretreatment at 1050 W/m2 and duration between 12 and 15 min is recommended for Sakha 3 and 6. After the oil extraction and storage period (4 weeks), PV increased in all the investigated oil samples. In general, the heat-treated seeds’ oil will stay stable and maintain quality as long as the seeds are stored before the oil is extracted.