Investigating some physical and functional properties of peppermint powder encapsulated by spray drying: effect of different storage conditions on phenolic compounds and antioxidant activity of the obtained powder

Recently, essential oils of plants such as peppermint have gained more interest due to their antibacterial, antifungal, antioxidant activity and free radicals scavenging ability. Microencapsulation by spray drying is a common method to preserve volatile and heat/oxygen sensitive compounds. This method retains essential and volatile compounds of peppermint against chemical spoilage and helps to improve handling properties of the obtained powder. The aim of this study was to investigate some physical and functional properties of spray dried peppermint powder, and to study the effect of storage conditions on phenolic compounds and antioxidant activity of the resulting powder. For this purpose, three air temperatures (140, 160 and 180 °C), three Arabic gum concentrations (10, 20 and 30 % w/v) were used. Bulk and tapped densities, repose angle, Husner ratio, total phenolic content (TPC) and free radical inhibition ability (DPPH) of the powders were measured. Powders were stored under three different atmosphere namely day light (25 °C), darkness (25 °C) and fridge (4 °C) for 120 days. Then, the TPC and DPPH of stored powders were measured at time intervals of 30 days. Results showed that increasing inlet air temperature and career substance concentration led to decrease in bulk and tapped densities and Husner ratio. TPC of powders were decreased by increasing inlet air temperature. However, at higher temperatures (160 and 180 °C), increasing Arabic gum concentration increased TPC of powders. Results of storing powders for 120 days indicated that storage conditions under low temperatures and darkness could more preserve TPC and DPPH scavenging ability of peppermint powders.