Novel Drying Techniques for Spices and Herbs: a Review

Spices and herbs are important parts of human daily food consumption and play an essential role in seasoning and/or preserving food, curing illness, and enhancing cosmetics. Proper processing is necessary because the fresh produce has high moisture content and often high load of microorganisms. Dehydration is the most common method used to lower moisture content and hence the water activity to a safe limit which prolongs shelf life. However, consumers' demand on processed products with most of the original characteristics of the fresh plants has increased. Consequently, drying must be executed carefully in the interest of retaining the taste, aroma, color, appearance, as well as nutritional value of the plants to maximum possible extent. In addition to quality considerations, drying efficiency is another key aspect for evaluating drying performance. This article reviews recent developments in the production of high dried spices and herbs. It attempts to detail the relative merits of selected recently developed drying techniques with focus on solar-assisted and microwave-assisted hybrid drying techniques which offer high-quality drying with excellent efficiency. Outlook for future research trends and challenges for dehydration of spices and herbs is also discussed.