RESUMO
Helianthus annuus L. seed hull is an abundant waste of the edible oil industry. To envisage potential applications of this waste, here, we aimed to analyze the chemical composition of milled sunflower hulls (SP), constituted mainly by 210 µm (51.4%) and 420 µm (27.6%) average mesh particle sizes. SP contained almost 30% of cellulose, 26.4% of lignin, 38.5% of neutral sugars, mainly hemicelluloses, and only 1.3% of proteins. The important lignin content and low pectin content (4.0% of uronic acids) present in SP were both ascribed to its low hydrophilic behavior and hydration capacity. Phenolic compounds were mostly proanthocyanidins (168 mg/100 g SP), with lower amounts of extractable (31.4 mg/100 g SP) phenolics (O-caffeoylquinic acid), all of them associated with the DPPH radical scavenging capacity (95 mg ascorbic acid equiv./100 g) and ferric reducing power (FRAP: 152 mg ascorbic acid equiv./100 g) shown by SP. Esterified ferulic acid (52.9 mg/100 g SP) was also found, mostly as monomers and trimers. SP of 53 µm particle size was then assayed as a filler (0, 5, 8, and 12% concentrations) in calcium low methoxyl pectin-based films, which showed antioxidant capacity (DPPH and FRAP assays) in an SP-concentration-dependent manner. SP showed homogeneous dispersion in composite films equilibrated at 57.7% relative humidity. Water content decreased while film thickness increased with SP concentration. When loaded at a 12% level, the presence of 53-µm SP decreased the water vapor permeability and increased the normal stress at film fracture. Sunflower hulls can then be applied to the development of active materials like 12% SP film, which can be proposed as a food slice antioxidant separator to be investigated in a future work.
RESUMO
Considering the polysaccharide composition and 32% of crystallinity of the water insoluble fiber extracted from corn husk (CHF) agricultural residue, its filler performance as water vapor permeability (WVP) and mechanical modifier in edible films based on commercial low methoxyl pectin (LMP) was evaluated (0, 1, 3, 5, 8% concentrations). The 53-µm-CHF carried phenolics and carotenes, and composites showed antioxidant capacity. Homogeneous films with a continuous LMP matrix were obtained. The 5%-CHF composite showed the highest surface contact angle (44°) and tensile strength, without change in elongation, while WVP was decreased in the 3-8% CHF-LMP-films. The latter was ascribed to the CHF-filler crystallinity whereas the improvement in mechanical performance and contact angle was attributed to a CHF-interconnected network formed at 5%-CHF critical concentration. Corn husk residue can be utilized as a source of fibers for material development. Composites with enhanced performance can be an antioxidant strategy at food interfaces.
Assuntos
Embalagem de Alimentos , Pectinas/química , Resistência à Tração , Zea mays , PermeabilidadeRESUMO
The effect of particle size (53, 105 and 210 µm) of carrot fiber (CF) on their hydration properties and antioxidant capacity as well as on the performance of the CF-composite films developed with commercial low methoxyl pectin (LMP) was studied. It was determined that CF contained carotenoids and phenolics co-extracted with polysaccharides (80%), rich in pectins (15%). CF showed antioxidant activity and produced homogeneous calcium-LMP-based composites. The 53-µm-CF showed the lowest hydration capability and produced the least elastic and deformable composite film due probably to CF bridged by calcium-crosslinked LMP chains. Antioxidant activity associated to the loaded CF was found in composites. When L-(+)-ascorbic acid (AA) was also loaded, its hydrolytic stability increased with the decrease in CF-particle size, showing the lowest stability in the 0%-CF- and 210 µm-CF-LMP films. Below ≈ 250 µm, the particle size determined the hydration properties of pectin-containing CF, affecting the microstructure and water mobility in composites.