Impact of Different Drying Methods on Nutritional, Colour Change, Solubility and Microbial Count of Selected Herbal Plant Powders

The research aimed to study the effect of drying processes (spray and freeze drying), and feed concentrations (80%, 65% and 50% of plant in water, w/w) on physicochemical and microbiological characteristics of star gooseberry (Sauropus androgynus), ceylon spinach (Basella alba), and cowslip creeper (Telosma minor). After drying, the powder recovery of herbal plant powders was up to 77.47%. The aw and moisture content of spray-dried powder (SDP) were lower than that of freeze-dried powder (FDP). The drying method did not significantly affect nutritional values of both powders, whereas the feed concentrations markedly affected the nutritional values of the powders. The fibre and fat contents of powder prepared from 80% feed concentration had the highest values (p<0.05). The dried star gooseberry powder was rich in protein (13.01-16.81%) and fibre (5.03-5.52%). The colour of FDP represented a smaller change than that of SDP. The dried powders prepared by 80% showed the highest solubility, up to 85.44%. The microbial counts of SDP were lower than that of FDP. The colour might well have been preserved by freeze drying, whereas a low moisture and microbial count were likely due to the spray drying.