Sustainable phenolic extraction from Olive mill wastewater: methods and environmental insights

Alifaki Y. O., Yilmaz M. S., Dogru I. S., Demir E. A., İŞCİ YAKAN A., ŞAKIYAN DEMİRKOL Ö.

Journal of Food Measurement and Characterization, 2025 (SCI-Expanded, Scopus) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Basım Tarihi: 2025
  • Doi Numarası: 10.1007/s11694-025-03708-6
  • Dergi Adı: Journal of Food Measurement and Characterization
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Agricultural & Environmental Science Database, CAB Abstracts, Compendex, Food Science & Technology Abstracts, Veterinary Science Database
  • Anahtar Kelimeler: COD, DES, Microwave, Ohmic, Olive mill wastewater, Ultrasound
  • Ankara Üniversitesi Adresli: Evet

Özet

In this study, microwave assisted extraction (MAE), ohmic assisted extraction (OAE), and ultrasound assisted extraction (UAE) of phenolic compounds from olive mill wastewater were investigated. Deep eutectic solvents (DES) were used as green solvents for extractions for three different molar ratios (1:2, 1:3, 1:4) and solvent types (choline-chloride: formic acid (C: F), choline-chloride: glycerol (C: G), choline-chloride: acetic acid (C: A)). DES: water ratio and wastewater: solvent ratio were kept constant at 1:1 and 1:5 for a sample volume of 100 ml, respectively. The effects of treatment type (microwave, ohmic, ultrasound or maceration), solvent type (choline-chloride: formic acid, choline-chloride: glycerol, choline-chloride: acetic acid) and solvent molar ratio (1:2, 1:3, 1:4) on total phenolic content (TPC), antioxidant activities (DPPH and ABTS inhibition values), pH values, total monomeric anthocyanin contents (TMAC), polymeric colour, colour density, polymeric colour ratio, and concentrations of some of the phenolic compounds of extracts were examined. In addition, FTIR values of different treated extracts which had highest TPC value were determined. Electrical conductivity values of ohmic treated samples were also calculated. The highest TPCs (approximately 14.500 mg GAE/g extract) were obtained at ohmic and microwave extraction. The ohmic and microwave extracts, which provided 93.75 and 87.5% time-saving compared to maceration, had higher TPC (14.500 mg GAE/g extract), higher AA (0.75 mg DDPH/g extract and 0.99 mg Trolox/g extract), and higher oleuropein, 2,4 hydroxyphenyl ethanol, hydroxytyrosol contents. The bands found in the FTIR spectrum were detected to be associated with oleuropein, 2,4 hydroxyphenyl ethanol and hydroxytyrosol. And as a final remark, it can be declared that the environmental impact of microwave extracts is minimal with dramatically decreased COD results (20 K to 2 K) and offers a sustainable solution.