Exploring the antioxidant and antibacterial capacities of Padina australis extracts, and their utilization in starch-based coatings for preserving rainbow trout (Oncorhynchus mykiss) fillets

This study aimed to investigate different extraction methods for obtaining phenolic compounds from Padina australis and evaluate their total phenolic content, antioxidative, and antibacterial activities. The extracts were further incorporated into a starch solution to create active coatings for rainbow trout (Oncorhynchus mykiss) fillets during cold storage. Results showed that microwave-ultrasound-assisted extraction yielded the highest phenolic content and extraction yield. Microwave, microwave-assisted, and microwave-ultrasound extraction methods exhibited the highest ABTS, DPPH scavenging activity, and FRAP, respectively. Additionally, microwave-ultrasound, microwave, microwave-ultrasound, and microwave-assisted extraction methods demonstrated the highest inhibition zone against various bacteria. Fish fillets treated with coatings containing extracts from microwave-ultrasound-assisted extraction exhibited the lowest peroxide values, free fatty acid content, total volatile basic nitrogen, and bacterial counts. These findings suggest that phenolic compounds from P. australis could be utilized in the development of active packaging with antimicrobial and antioxidant properties.