The viability of commercially relevant New Zealand seaweeds as a novel source of protein: The impact of processing on the extraction efficiency of protein

The world’s population is increasing and with it so too is the demand for food production specifically protein which is essential for human nutrition. However, relying solely on animal-based proteins is increasingly problematic given growing global environmental impacts. Thus, novel protein sources are increasingly investigated, particularly plant-based alternatives due to their smaller carbon footprint. Seaweeds hold potential as a novel protein source due to their relatively high protein content and quality as evidenced by essential amino acid content. However, seaweeds’ cell structure, with unique polysaccharides, complicate protein availability in terms of human digestion, necessitating procedures to disrupt the cell if seaweeds are to be a reliable protein source. This research thesis sought to investigate which of six New Zealand seaweeds (five different species) had the highest raw potential as a protein source, and if this protein’s extraction could be improved by food grade standard, industry relevant processing techniques. Seaweeds assessed included: Pyropia plicata wild harvested from the Tauranga, Bay of Plenty (North Island) and Kaikōura, Canterbury (South Island); Macrocystis pyrifera and Undaria pinnatifida provided by commercial supplier (NZ Kelp); and Ulva sp. B and Ulva ralfsii harvested from land-based cultivation at Coastal Marine Field Station (CMFS), University of Waikato, Tauranga. All six were analysed for proximate composition (C, H, N, S, and ash), content of protein (as amino acids), total lipids, carbohydrates, fibre, minerals, and heavy metals. Antioxidant capacity was evaluated as new research shows this can influence protein bioavailability. From these results Ulva sp. B and Ulva ralfsii were chosen as the potential protein sources with their protein content 151 mg/ g and 138 mg/ g, respectively. The effects of two alternative processing methods, which were applicable to industry for human nutrition, were then applied to these two species to assess their impact on the extractability of protein. The two chosen processing treatments were enzyme hydrolysis using a commercial mixture of enzymes (Viscozyme®) to target the chemical degradation of cell wall polysaccharides, and homogenisation to target the mechanical degradation of the cell wall structure. These were used alone and combined in a factorial experimental design and found that the combination of both processing methods yielded the greatest extraction efficiency 55.2% and 63.7% extraction efficiency for U. sp. B and U. ralfsii, respectively. While this study was limited in scope, it demonstrated the potential for cultivated seaweeds in New Zealand to be successfully processed to enhance their available protein and serve as a novel protein source for human nutrition