Extraction of biopolymers and phenolic compounds from sunflower agro-residues and their application to produce biodegradable active-packaging films

Sunflower processing industry produces large quantities of waste besides the oil, including the heads, stalks, hulls and meal. These residues have minimal applications and face disposal issues. Looking at the chemical composition, sunflower heads (SH) and stalks (SS) have a significant amount of pectin (15-25%) and sunflower meal (SM) has a high protein (approx. 30-40%) and phenolic content (1-4%). Currently, there is an increasing interest in developing edible packaging films from protein-polysaccharides composites to enhance the physical, biological and chemical properties of the composite films in comparison to protein or polysaccharide films alone. Additionally, incorporation of phenolic compounds in these composite films can further enhance the antimicrobial, antioxidative and UV-light blocking properties. So, this study aims to exploit the biopolymers and phenolics from sunflower industry wastes and develop novel biodegradable active-packaging films. Phenolic compounds from SM were first extracted via supercritical-fluid extraction followed by protein extraction via alkaline extraction-isoelectric precipitation. Pectin was extracted from SH and SS with ammonium oxalate and recovered by alcohol precipitation. Films were prepared by mixing proteins, pectin and glycerol (as plasticizer). Response surface methodology was used to optimize the pectin-protein-glycerol mixture for optimal film characteristics (mechanical properties, water and vapor permeability). Pectin and protein solutions were prepared separately and mixed with pectin such that final pectin, protein and glycerol concentration in solution were 0-0.5%, 0-2.5% and 0.5-2% respectively. The solutions were poured and solidified to obtain films that were eventually analyzed for mechanical and barrier properties. Sunflower phenolics (0-5%) were then added to optimal polymer mixture and phenolics-loaded films were reevaluated for mechanical, antioxidative, antimicrobial and biodegradability properties. Preliminary data showed SM contained 39% proteins and 8.81 mg gallic acid equivalent phenolics/g. Extracted protein isolates had 87.98% proteins with a recovery rate of 57.3%. Pectin and phenolics extraction and film development study is currently ongoing.