The effect of different drying methods on antimicrobial andantioxidant activity of stinging nellte, celery, red onion, ginger and umuravumba

Nowdays spices and herbals are becoming an interesting subject due to their poperties linked with thier antioxdent, antimicrobial and thier nutrition values. Some of those properties may be lossed during the drying method which is the most used perservation method for spice and herbals. In this study called the effect of drying method such as open air sun drying, oven drying at 40 and 60oC and freeze drying on DPPH radical scavenging, metal chelating, total phenolic component and antimicrobial activity were investigated.In terms of antioxidant properties, the activity changed significantly according to the origin of the extract and the applied drying method; The open air sun drying method showed to be a good drying method to maintain the functional quality and value of the samples and this was followed by drying at 60°C. The highest DPPH value was found in the open-air sun dried extract (94.50±0.59%) of the umuravumba; Metal chelating value was obtained from open air sun dried extract of the stinging nettle (48.540±0.37%) and phenolic high content value was found in the freeze-dried extract of Iboza riparia (2855 mg GAE / L).Stinging netlles and celery showed antimicrobial effect on B. subtilis, ginger and umuravumba showed effect on both B. subtilis and L. monocytogenes strains while red onion extracts did not show any antimicrobial activity on the microorganisms tested in the study. The antimicrobial activity of the extracts varied according to the sample origin and drying method. The highest antimicrobial effect on B. subtilis was found in freeze-dried celery (17 mm zone); and the highest antimicrobial effect on L. monocytogenes was found in the open air sun dried ginger (12 mm zone).For the killing time experiments of extracts with antimicrobial activity the greatest decrease in the initial number of 6 log CFU/mL occurred following the first treatment for the majority of the samples. The drop below the detectable count varied between 24 hours after treatment and immediately after treatment, depending on the origin of the extract and the used drying method, but not for other drying methods except for celery.Umuravumba grown in tropical countries has good antioxidant and antimicrobial activity among the tested samples; It has been concluded that the choice of drying method is effective on the antioxidant and antimicrobial properties of the products, where it is encurraged to increase the studies on this plant.