Influence of drying conditions on the quality ofOriganum syriacumL.

Abstract

The temperature and the speed of drying may affect the quality of the end product of medicinal plants. In addition, ecotypes and chemotypes could be factors influencing this quality. Thus, the aim of our study was to explore various techniques of drying of Origanum syriacum L., which is considered as a main ingredient in the Lebanese diet. For all these reasons, we decided to study two types of O. syriacum originating from Rkai and Ibrine regions on which analyses were carried out. In view of our results, a moderate temperature, in the absence of light, is more favourable for the safeguarding of the flavours and chlorophylls. On the other hand, these conditions seem to be unsuitable for other substances. In order to clarify the optimal conditions for drying of O. syriacum to lead to a product of quality, the choice of a technique of suitable dehydration seems to be delicate.

Comparison between Quality Traits of Solar-Dried and Freeze-Dried Origanum syriacum L. (Za’atar)

“…Drying temperature had critical effect on chlorophyll and carotenoids contents of O. syriacum. High drying temperature led to higher destruction chlorophyll and carotenoids contents in comparison to low drying temperature [8].…”

Origanum syriacum L. (Za’atar), from Raw to Go: A Review

“…Once drying of za’atar is achieved, it can be stored for several months if the storage area is dry and isolated from moisture, sunlight, heat, and polluting substances. Dried za’atar can be manually or mechanically threshed [ 18 ]. Za’atar grinding is the next step after threshing and sieving dried flowers and leaves to further mix with other ingredients to produce the za’atar mix.…”

“…Another study found that drying at a lower temperature was better for preserving chlorophyll and carotenoids contents in O. syriacum, while drying at a higher temperature produced O. syriacum with higher phenols content. It was also reported that shade drying at lower air velocity was the best for preserving alpha-tocopherol content [ 18 ]. Every processing method has its strengths and weaknesses, and every quality trait in za’atar responds differently to processing conditions.…”

“…The higher levels of TP content and antioxidant capacity in vacuum oven-dried samples than freeze-dried samples might be due to the reactivation of degradation enzymes in freeze-dried herbs or the release of phenolic compounds by the high heating temperature during vacuum oven-drying. Wakim et al [ 18 ] studied the influence of various drying conditions on the quality of two types of Lebanese O. syriacum from Rkai and Ibrine regions. Solar drying, shade drying, and four drying treatments using forced air artificial dryers with two different temperatures (26 and 45 °C) and two different air speeds (0.1 and 0.2 m/s) were used.…”

“…Drying temperature Loss of essential oil by evaporating at drying temperatures higher than 30-35 • C. [7] Drying at a lower temperature is better for preserving chlorophyll and carotenoids contents. [18] Air-drying The best for preserving the aroma, flavor, and color compared to oven and freeze-drying. [16,17] Vacuum oven-drying Higher levels of total phenols content and antioxidant capacity compared to freeze-drying.…”