Extraction efficiency and characteristic evaluation of turmeric oleoresins; A potential functional ingredient

Oleoresins are key flavoring and coloring ingredients in spices and herbs. Among spices, turmeric is most commonly used all around the world. Turmeric oleoresins have a promising future in pharmaceutical and food processing industries as functional ingredients. Apart from conventional extraction methods, by using modern extraction methods, a higher yield of oleoresins can be obtained with minimal effects on their characteristic parameters including phytochemicals, antioxidants, volatiles, nonvolatiles and fatty acids profile. In the present research, turmeric oleoresins were extracted by 5 different extraction methods and were compared for extraction efficiency and characterization. Turmeric samples were dried, and their moisture content was further adjusted to 12% prior to extraction to get maximum extracts during extraction process which may be affected due to higher moisture content. Extraction was carried out by (i) conventional solvent extraction (hexane, acetone, petroleum ether, diethyl ether and iso-propanol), (ii) steam distillation, (iii) 3-phase partitioning, (iv) Supercritical fluid extraction/SCFE and (v) solvent extraction followed by cryogenic grinding. The results revealed that the highest extraction efficiency was observed in solvent extraction after cryogenic grinding (4.85%). Total phenolic content (TPC), total flavonoids content (TFC), 2, 2diphenyl-1-picrylhydrazyl (DPPH), Ferric reducing antioxidant power (FRAP) and Lipoxygenase (LOX) inhibition assay were determined through UV-vis spectrophotometer, functional characterization was carried out by Fourier transformed infrared (FTIR) spectroscopy while fatty acids profiling was carried out by gas chromatography attached with flame ionization detector. Total volatiles and non-volatiles were also determined by oven drying method. Characteristically, oleoresins extracted through SCFE were found to be a rich source of TPC (20.57 mg GAE g-1), TFC (109.00 mg QE 100g-1) and total volatiles (2.23%) while highest non volatiles were observed in extracts obtained after cryogenic grinding. Similarly, the highest antioxidant activities assessed by DPPH and FRAP were indicated by oleoresins extracted through SCFE as 59.55% and 220.60 & mu;M Fe2+ g-1, while highest LOX activity (58.33%) was observed in extract obtained by 3-phase partitioning. FTIR spectroscopic analysis of the selected sample indicated the presence of different functional groups with bond type at different wave numbers. GC-FID analysis of selected sample indicated the presence of 13 different fatty acids ranging from 1.9-18.6%. Pentadecane was found in lowest percentage while cis-10 pentadecanoic acid was found in highest concentration. It was concluded that although the extraction % of SCF extract was slightly lower (4.07%) but it was found best in term of purity and characterization with a strong potential to be used in food and other industries. Keywords: Turmeric oleoresins, extraction, characterization, Phytochemicals, fatty acids profiling.