Phlorotannins from New Zealand brown seaweeds: Extraction, antioxidant activity, and food applications

• Seaweed has cultural significance for Māori, valued as food, medicine and taonga. • Brown seaweed serves as a rich source of polyphenolic compounds called phlorotannins. • Phlorotannins can potentially replace synthetic antioxidants in food products. • Current research gap underscores the need to understand polyphenol properties in food matrices. Brown seaweed, a type of marine macroalgae, is a sustainable resource for human consumption that plays an important role in several cultures, including Aotearoa New Zealand. Brown seaweeds have a relatively high content of phenolic compounds and, exclusively, phlorotannins, which have garnered increasing attention due to their bioactive properties. Applications of these phenolic compounds have been developed for therapy, food additives, material manufacturing, and fertilisers. Among these, their antioxidant property is especially important for the food industry, but limited research has been conducted. This review investigated the nutrition profile of New Zealand brown seaweed species, which are rich in macronutrients, and addressed safety concerns regarding heavy metals and iodine. Phlorotannin content, extraction methods, and their promising antioxidant activities were then compared between New Zealand and global brown seaweeds. According to the current research, they have comparable phlorotannin content and antioxidant activities. More importantly, the potential of applying brown seaweed species as an antioxidant in food matrices was explored. Although successful trials have utilised (New Zealand) brown seaweed extracts as antioxidants for various foods, their widespread commercial use remains rare. The seaweed industry in New Zealand has not been established, and the seaweed is heavily reliant on wild harvest and imports. In conclusion, more effort is needed to develop a comprehensive, evidence-based understanding of New Zealand's brown seaweeds, ultimately enabling the commercialization of this promising resource as antioxidants in food products.