Physicochemical properties of winter savory extracts prepared using ultrasound-assisted extraction

Abstract

This study aimed to assess the optimal extraction parameters, solvent-to-solid ratio, and extraction time, for ultrasound-assisted extraction of Satureja montana L. (winter savory) harvested from a 6-year-old experimental plantation. The optimization was performed in order to acquire extracts that are rich in the content of polyphenols (TPC), flavonoids (TFC), and proteins, and also exhibit strong antioxidant activity, while maintaining satisfactory physical characteristics. Besides this, the influence of UV irradiation on the physicochemical properties of the selected extracts was also analyzed. The TPC values increased with longer extraction time and higher ratio (ranging from 41.4 to 56.9 mg gallic acid equivalent (GAE)/g for the ratio 30:1, and 52.4-58.4 mg GAE/g for 40:1), and the TFC followed the same trend. Total protein content values increased with the increase in the solvent-to-solid ratio, while the extraction time had no significant influence. All used antioxidant assays showed better activities when a higher solvent-to-solid ratio has been performed. pH values ranged from 6.00 to 6.46. The extraction time and solvent-to-solid ratio did not significantly influence the conductivity, whereas the zeta potential was significantly affected. The highest density was detected in the extract acquired at a 40:1 ratio after 30 min (0.994 g/mL), and higher viscosity of the extracts attained at a 30:1 ratio compared to the parallels at a 40:1 ratio. According to the results of UV stability, UV light significantly affected the TPC, TFC, total proteins, ABTS radical scavenging, cupric, and ferric ion-reducing activities, with a positive effect on ferric ion-reducing potential, and the denisty. In conclusion, the extraction conditions that yielded the best phenolic-rich extract with good antioxidant potential and satisfactory physical properties were a 40:1 solvent-to-solid ratio and a 30 minute extraction time.