Drying Technologies: Vehicle to High-Quality Herbs

Abstract

Herbs are usually marketed as dry due to a consumer demand beyond their seasonality; dehydration leads to a stable, easily moveable product that is available throughout the year. The process of drying, though, leads to modifications in the appearance, composition and quality of the raw material. The extent of these alterations depends on the applied drying methodology and its parameters, rendering the optimization of this process imperative. Numerous studies examining the effect of drying on the main characteristics of herbs have been published in recent years, and this review aims at organizing the available information of the studied herbs, drying methods and measured parameters in a comprehensive manner. Primarily, since aroma is the main characteristic of herbs and the principal aim for the end product is to retain the raw material's character, this review will focus on the most widely studied effect of drying, which is the essential oil yield and composition. Secondly, results from various studies on the influence of drying on biochemical compounds, organoleptic properties of dried herbs are also presented. The most common approach to the study of drying kinetics is also presented. Finally, novel technologies targeting to minimize the magnitude of changes from the raw material are described.

Changes in the Content of Phenolic Compounds and Biological Activity in Traditional Mexican Herbal Infusions with Different Drying Methods

“…Drying is necessary as a means to remove moisture and ensure that the product is enzymatically and microbiologically stable. However, previous research has also focused on the drying of various herbs associated with highly biologically active components [26]. Approximately 85% of these traditional herbs contain phytochemicals, which confers beneficial effects on health.…”

Structural and health functionality of dried goji berries as affected by coupled dewaxing pre-treatment and hybrid drying methods

“…[7,9] In terms of freeze drying, owing to the low temperature and the deficiency of water required for the process, many microbiological reactions are mostly inhibited which extends to an excellent quality of the final product. [10] However, its operation cost is much higher than other drying methods. Every drying technique has advantages and restrictions.…”

Influence of Air-Drying on the Quality Characteristics of Spearmint: Effects of Air Temperature and Velocity

“…The main objective of drying is to lower water levels to less than 15% in order to inhibit microbial growth and spoilage, preserving at the same time as much as possible from the fresh material characteristics (Orphanides et al 2016). Indisputably, color is the primary indicator for consumer acceptance and is associated with better flavor expectation, especially from a dried product (Garber et al 2000;Demirhan and € Ozbek 2009).…”

“…The use of high temperatures causes the decomposition of bioactive and colorful components leading to a dramatic reduction in quality of dried aromatic plants. The effect of air velocity on quality of end products had been also described (Orphanides et al 2016). Regarding to food safety, higher temperatures lead to a greater killing effect of bacteria.…”