Development of active packaging materials from olive mill solid waste

Polyvinyl alcohol (PVA)/Lignin composite nano fibers were fabricated from lignin obtained from olive mill solid waste (OMSW). Deep eutectic solvent (DES) prepared with choline chloride, glycerol, and aluminum chloride hexahydrate was used to extract lignin from OMSW. After the pretreatment cellulose rich (CRF) and lignin rich fractions (LRF) were obtained. Effect of aluminum chloride hexahydrate concentration on DES pretreatment was investigated. Delignification ratio of choline chloride: glycereol: AlCl3.6H2O (1:2:0.1 molar ratio) DES was higher (39.21 ± 0.35 %) as compared to other aluminum chloride hexahydrate concentrations. Highest antioxidant activity and purity of the LRF obtained after DES pretreatment was measured as 437.88 ± 7.14 (mmol TEAC/Kg sample) and 87.21 ± 0.36 %. Changes in structure of OMSW during pretreatment were also determined with FT-IR spectrometry. Peaks representing lignin (C=C stretching) were become sharper on spectra of LRF at the same time they were decreased on spectra of CRF. Changes observed over hydrogen bonding related peaks as well. Cellulose related peaks (weak C-O stretching and C-H bending vibration of glucose unit) were increased on spectra of CRF and decreased on spectra of LRF. LRF obtained from DES pretreatment used in production of defect free fine antioxidant poly(vinyl alcohol)/lignin composite nanofibers. Average diameter was 126 ± 17 nm and antioxidant activity was 85.84 ± 1.63 (mmol TEAC/Kg sample) at 4% lignin. Increasing lignin level resulted in higher antioxidant activity and samples containing 12% lignin had the highest antioxidant activity 131.15 ± 3.13 (mmol TEAC/Kg sample). In order to reveal the effect of electrospinning on the antioxidant activity, PVA/lignin composite films were fabricated, and their antioxidant activity was compared with that of nanofibers. Fiber formation was increased antioxidant activity of films up to 68%. Effect of electrospinning conditions like flow rate, distance and total solid concentration on fiber morphology determined by scanning electron microscopy (SEM). Optimum electrospinning conditions were 19.5 cm distance and 1.00 mL/hr flow rate. As a result, antioxidant PVA/lignin composite nano fibers were fabricated from LRF produced from OMSW via DES pretreatment. To our knowledge there is no other study reported on production of nanofibers from LRF obtained from OMSW. Production of such fibers may used in food packaging area and this might led to valorization of a nature polluting waste.