Abstract
This study explores the preparation of antioxidant starch food packaging materials by the incorporation of valuable phenolic compounds extracted from sunflower hulls, which are an abundant by-product from food industry. The phenolic compounds were extracted with aqueous methanol and embedded into starch films. Their effect on starch films was investigated in terms of antioxidant activity, optical, thermal, mechanical, barrier properties and changes in starch molecular structure. The starch molecular structure was affected during thermal processing resulting in a decrease in molar mass, smaller amylopectin molecules and shorter amylose branches. Already 1–2% of extracts were sufficient to produce starch films with high antioxidant capacity. Higher amounts (4–6%) of extract showed the highest antioxidant activity, the lowest oxygen permeability and high stiffness and poor extensibility. The phenolic extracts affected predominantly the mechanical properties, whereas other changes could mainly be correlated to the lower glycerol content which was partially substituted by the extract.
Highlights
There is an increasing interest to exploit by-products from food industries as matrices and additives in packaging materials contributing to the material and process sustainability towards a circular bio-based economy
This study shows the potential use of utilizing sunflower hulls as a valuable source of a natural antioxidant extract
Different amounts of the phenolic extract, 1-6 wt% based on the starch-glycerol formulation for films, were successfully incorporated into compressionmolded films preserving their antiradical activity against DPPH*
Summary
There is an increasing interest to exploit by-products from food industries as matrices and additives in packaging materials contributing to the material and process sustainability towards a circular bio-based economy. An illustrative example of the potential of such byproducts are sunflower hulls. Sunflower hulls are a by-product from sunflower seed production and exhibit very low nutritional value for human and animal nutrition due to their low digestibility. The hull represents between 20-30% of the sunflower seed and is often removed before oil extraction or snack processing. Sunflower hulls have a great antioxidant activity due to a high value of total phenolic compounds (Velioglu, Mazza, Gao, & Oomah, 1998) that could have potential for obtaining antioxidant extracts. De Leonardis, Macciola, and Di Domenico (2005) extracted an antioxidant product from sunflower hulls that was reported to be economically suitable. There has been a patent on a natural red sunflower anthocyanin colorant with naturally stabilized color qualities as coloring agent in food products, cosmetics and pharmaceuticals (Fox, 2000)
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