Sage processing from by-product to high quality powder: I. Bioactive potential

Nowadays, valorization of food industry by-products and agricultural waste has been in the focus of investigation worldwide. Therefore, the aim of this study was utilization of sage (Salvia officinalis L.) herbal dust, by-product from filter tea factory, for production of high-quality dry extracts by spray drying technique. Liquid feed for spray drying was obtained using conventional (maceration (MAC) and hydrodistillation (PHD)) and novel (ultrasound-assisted (UAE), microwave-assisted (MAE) and subcritical water extraction (SWE)) extraction techniques, whereas sage by-product from filter tea factory was used as raw material. Dry powders were characterized in terms of polyphenol content (total phenols (TP) and total flavonoids (TF)), antioxidant activity and antimicrobial activity towards selected gram-positive bacteria strains. Particularly high TP and TF were observed in all dry extracts (90.20-290.28 mg GAE/g and 56.98-154.88 mg CE/g, respectively), while applied extraction technique had significant effect on polyphenol content. Antioxidant activity was determined by DPPH, FRAP and ABTS assays and extracts obtained by MAC, UAE and MAE were more potent comparing with SWE and PHD. In case of antimicrobial activity, all investigated samples exhibited certain antimicrobial effects towards selected Gram positive bacteria (MIC < 50 mg/mL). Good correlation between polyphenol content, antioxidant potential and antimicrobial activity was observed, whereas sample obtained by UAE had the best balance of biochemical properties.