Intermittent Microwave-convective Air Drying of Oregano

Abstract

Effectiveness of intermittent microwave-convective air drying (IMWC) was investigated and compared to continuous microwave-convective air drying (CMWC) and convective air drying for oregano. Both CMWC and IMWC increased the drying rate of oregano compared to convective drying. The CMWC and IMWC were 12.714.0 and 4.711.2 times more energy efficient in drying than convective drying, respectively. The highest essential oil contents were obtained from convective drying at 40 C and 45 C. However, these treatments had the longest drying time and the highest energy consumption. The CMWC yielded the lowest essential oil content and resulted in an extreme change in the essential oil composition. The IMWC, except with the pulse ratio of 3.0, resulted in similar essential oil content compared to convective drying at 50 C and shade drying. No identical result was found among the prevailing compounds of essential oil of oregano obtained from shade drying, convective drying and IMWC. Both CMWC and IMWC did not yield acceptable results of product color. However, in terms of essential oil content and quality, the IMWC at 25 C room temperature with the pulse ratio of 5.0 was judged as the most suitable drying method for oregano due to its rational drying time and energy consumption compared to CMWC drying, convective air dying, and shade drying.

Real-time color change monitoring of apple slices using image processing during intermittent microwave convective drying

“…The downward drying rate trend, created by reduction in moisture content resulting in low microwave energy, was absorbed by the sample (Feng et al, 2002). Similar drying curves were reported for intermittent microwave-convective air drying of red pepper (Soysal et al, 2009b), sage leaves (Es¸tu¨rk, 2012), oregano (Soysal et al, 2009a), and dill (Es¸tu¨rk and Soysal,Figure 7. The interaction of PR and microwave power on drying rate.…”

“…Intermittent microwave convective air drying (IMWC) has been successfully used for a limited number of agricultural products such as potato and carrot (Chua and Chou, 2005), sage leaves (Es¸tu¨rk, 2012), red pepper (Soysal et al, 2009b), dill (Es¸tu¨rk and Soysal, 2010), apple (Aghilinategh et al, 2015), and oregano (Soysal et al, 2009a). Color is the most important factor of dried food for quality evaluation and consumer acceptability (Bal et al, 2011) since changes may occur during drying which make the food taste unpleasant, and color can be an indicator of these undesirable changes.…”

Optimization of intermittent microwave–convective drying using response surface methodology

“…IMWC air drying has been successfully used for a number of agricultural products such as potato, carrot (Chua and Chou ), sage leaves (Esturk ), red pepper (Soysal et al. ), and oregano (Soysal et al. ).…”

Peppermint Drying Performance of Contact Dryer in Terms of Product Quality, Energy Consumption, and Drying Duration

“…[11,12] Microwave drying has been shown to drastically shorten drying time but causes considerable essential oil loss and color change. [13] Therefore, microwave dryers should be continuously monitored and elaborately controlled to preserve the product quality. These requirements increase manufacturing and operating costs.…”