THE EFFECT OF INTERMITTENT COOLING DURING DRYING ON PHYTOCHEMICAL CONTENT OF MISAI KUCING (ORTHOSIPHON STAMINEUS)

Misai kucing (Orthosiphon stamineus) is one of the priority herbs under the Entry Point Projects (EPP) of the National Key Economic Areas (NKEAs) which has been identified by Ministry of Agriculture (MOA), Malaysia. Most herbs including misai kucing are always consumed in dried form, so drying is the most important process in herbal preparation. Efficient drying technique needs to be established in order to produce herbal products of a premium quality for maximum health benefits. Improper drying will cause reduction in product quality especially the content of bioactive compounds. Continuous drying is the most common method used by herbs producers in Malaysia and its effect on phytochemical content is well documented. However, there is a need to explore other drying technique such as adopting intermittent cooling process during drying for highest retention of phytochemicals in herbs. Stopping the drying process temporarily and putting the material under ambient condition is called intermittent cooling or ambient resting. So, this paper discusses the possibility to adopt intermittent cooling during drying of misai kucing. The effect of intermittent cooling time during drying on phytochemicals retention in misai kucing was investigated using a cabinet dryer. Intermittent cooling of 2 h during drying showed better retention of phytochemical contents in misai kucing as compared with continuous drying. The drying time and drying rate were not significantly affected by intermittent cooling treatment. Intermittent cooling for 2 h showed better retention of total flavonoid and rosmarinic acid contents. The level of rosmarinic acid which is the marker compound of misai kucing remained high after 2 h treatment.