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 12.7-14.0 and 4.7-11.2 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.

Black garlic is a relatively new product that has become very popular in recent years. It is obtained by fermenting raw (white) garlic by the application of heat treatment. The undesirable pungent odor of the white garlic disappears and the black garlic product with a sweet-sour flavor is formed after various reactions during the applied heat process. As a result, black garlic is more preferred and easily consumed by the consumers compared to white garlic. This review aims to summarize the studies on the changes in the odorants during the heat treatment employed in the production of black garlic as well as the factors affecting the changes in the aroma and aroma-active compounds and the use of molecular sensory science (MSS) approach, which has been applied in recent years as a new method for the determination of the aroma compounds. This work revealed that the use of the MSS on the aroma changes in black garlic is quite limited in the literature. Thus, more studies are needed to understand the aroma changes that occur during the formation of black garlic from white garlic in more detail.