Antioxidant Capacity Evaluation of Porphyran Extracted from Porphyra Dioica: Incorporation in Films for Food Packaging

Increasing the shelf life of food is a constant challenge in the food industry. In recent years, edible coatings and biodegradable films have been considered one of the most promising technologies to achieve this goal, ensuring microbiological safety and food protection from the influence of external factors. The potential assessment of algae polysaccharides as a substitute for petroleum-based plastics has been the focus of many scientific efforts. Films derived from alginate, agar and carrageenan have been widely studied, due to their gelling properties and film-forming ability, which are already well established, however, there is scarce information regarding films derived from porphyran, a sulphated galactan which is produced by the red macroalgae belonging to the Porphyra taxonomic genus. In the present study porphyran was extracted using a Soxhlet system and water as a solvent, following precipitation and washing with isopropanol with a yield of 26.63 ± 0.29% for the semi-refined porphyran, with 67.74 ± 4.13% of D-galactose and protein not detectable by p-Benzoquinone assay. The antioxidant capacity was evaluated through different methods: the DPPH and ABTS radical scavenging activity, 6.49 ± 1.2% and 13.83 ± 1.5%, respectively, the HPSA scavenging activity, from a ΔAbs of 0.089 ± 0.004 to 0.069 ± 0.008, the ferric reducing/antioxidant power, FRAP, 0.4 ± 0.003μg mL−1 equivalents of ascorbic acid and the total polyphenols content, QTP, 1.2 ± 0.006 μg mL−1 equivalents of gallic acid.