Effect of different concentrations of Arabic gum and different drying temperatures on physiccal properties of spray dried peppermint extract powder

Peppermint is an aromatic herbal plant in which its essential oil possesses many polyphenolic compounds with anti-bacterial, anti-fungal, antioxidant and free radicals scavenging properties. Microencapsulation by spray drying is one of the most effective methods which has increasingly being used in recent years. This process is regarded as an important industrial operation for physical coating of liquid or semi-liquid foods with a thin layer of protective layer to preserve them against any chemical spoilage, to increase powder productivity, to facilitate dry blending of powdered food with other ingredients and finally, to increase the shelf life of dried food. The objective of this study was to investigate different concentrations of carrier substance, Arabic gum (AG) and different inlet air temperatures on production yield of powder and different physical properties of spray dried peppermint powder.

A co-current pilot scale spray drier with rotating atomizer was used. AG as a drying aid substance at concentrations of 10, 20 and 30% (w/w) was used. Inlet air with a temperature of 140, 160 and 180 °C was used at a co-current stream with feed material. In all experiments, atomizer rotational speed, raw material feeding rate, feed temperature, and air nozzle pressure were 18000 rpm, 25 ml/min, 30±1 °C and 4.2±0.1 bar, respectively. Moisture content, aw, production yield, solubility, hygroscopicity, wettability, and objective color parameters of spray dried powders were determined. Inlet air with a temperature of 140, 160 and 180 °C was used at a co-current stream with feed material. In all experiments, atomizer rotational speed, raw material feeding rate, feed temperature, and air nozzle pressure were 18000 rpm, 25 ml/min, 30±1 °C and 4.2±0.1 bar, respectively. Moisture content, aw, production yield, solubility, hygroscopicity, wettability, and objective color parameters of spray dried powders were determined.

Results showed that increasing inlet air temperature and AG concentration (up to 20%) led to an increase in production yield. However, concentrations more than 20% decreased production yield. Hygroscopicity of powders was increased with temperature, and decreased with increasing in concentrations of AG. Moisture content, aw, wettability, solubility were decreased with increasing in air temperature and AG concentrations. The results of objective color measurement revealed that increasing in air temperature and AG concentration led to an increase in L*; However, a*, b*, chorma and hue indices were decreased.

It was concluded that the inlet air temperature of 160 °C and Arabic gum concentration of 30% were the optimal parameters in spray drying of peppermint yeast extract.