Are New Zealand native Pyropia and Porphyra seaweeds (karengo), an opportunity for creating high-value foods from alternative proteins?

Karengo – a native variety of nori with potential as a high-value food ingredient.

The research team, comprising researchers from Cawthron Institute in Nelson, the Riddet Institute at Massey University in Palmerston North, Plant&Food Research at Palmerston North and the University of Auckland, along with two research institutes in Singapore, are investigating how to unlock the nutritional and health-promoting potential of a group of red seaweeds from the genera Pyropia and Porphyra. This group of seaweeds includes nori, familiar as the wrapper for sushi, as well as a number of species found only in New Zealand and which are a traditional food of Māori, known as karengo or parengo. Each research institute is contributing their distinct expertise in seaweed biology and food analysis, food processing, protein extraction from terrestrial plants, and food science to create an international multidisciplinary team, the likes of which have not previously been applied to this challenge.

“Karengo has great potential as a high-value functional food and a unique food ingredient,” says the team’s leader, Dr Tom Wheeler of Nelson’s Cawthron Institute. His research team at Cawthron has previously investigated the chemical composition of several species of karengo through a two-year programme funded by the High-Value Nutrition National Science Challenge. The team found that karengo contains 30-35% protein as a percentage of dry weight – which could be a higher level of protein than any terrestrial food plant, 2% omega-3 fatty acids, almost all of which is eicosapentaenoic acid (EPA), and up to 70 ug/100g vitamin B12. This last observation is of particular interest to the team, as it predicts that as little as a 5 g snack of karengo would provide the recommended daily allowance of this vitamin. This is particularly relevant for vegans, who often have difficulty obtaining adequate levels of vitamin B12 through their diet. “One day karengo extracts could be the basis of meat substitutes which look and taste like the real thing as well as providing a good nutritional substitute for meat. The karengo protein extract even has a meat-like red colour” adds Dr Wheeler.

Working with Wakatū Incorporation and Te Rūnanga o Ngāi Tahu is critical to realising this long-term goal, particularly as karengo is regarded as a taonga species. “We hope that one day we will be marketing high-value health-promoting products to niche overseas consumers based on sustainable low-impact aquaculture of karengo here in Te Waipounamu,” says Wakatū Incorporation’s Chief Scientist, Professor Charles Eason.

Processing to extract protein from Pyropia/Porphyra seaweeds.

In their latest research, the team has focused on unlocking the potential of karengo protein through processing. They have joined forces with some of New Zealand’s prominent food science and technology institutes to devise and implement a process at the pilot plant scale to produce a protein-enriched extract and evaluate its attributes. The project also will assess the digestibility and bioavailability of the protein and the physico-chemical attributes of the extract.

“The goal of our collaboration is to create a novel food ingredient in which the protein is easily digested and yet retains some of the beneficial attributes of the whole karengo,” says Dr Arup Nag, who leads the Riddet Institute section of the team. To avoid difficulties in supply of biomass for New Zealand native species of Pyropia or Porphyra, the team has obtained a large quantity of food grade dried Porphyra umbilicalis from a commercial source, working with New Zealand-based seaweed importer and retailer, Pacific Harvest. The team has used this material to investigate the effect of a range of parameters, including rehydration conditions, pH, particle size reduction and enzymatic digestion on the yield of protein extracted into the aqueous phase during extraction. This has resulted in yields of up to 50% of the total protein being extracted at the lab scale. “This is actually quite an impressive achievement,” says Dr Wheeler, “as a similar project in Europe extracted only 20% of the protein present”.

However, transferring a lab-based procedure to a pilot plant scale process is often challenging, and this indeed proved to be the case with Porphyra protein extraction. The team has had to adapt to the limitations of processing at this scale, with problems being encountered in a number of areas, including particle size reduction, phase separation and drying. “Understanding how to handle this type of seaweed at the pilot plant scale has proved to be a real challenge, and we have had to be innovative,” adds Dr Lee Huffman, the lead researcher from the Plant&Food Research Institute who is contributing to the programme. Nevertheless, the team has established a process that has produced 4 kg dry weight of extract, of which 50% is protein and 40% is soluble dietary fibre. “We expect that the process could be applied to New Zealand karengo with very similar results” says Dr Wheeler. However, there is still some way to go to establishing commercial viability. The protein yield was low compared with the lab-scale procedure, and some value would need to be realised from the side streams produced. “The efficiency of the process would need to be improved and a business case developed before we could say it is ready for implementation on a commercial scale” says Prof. Eason of Wakatū.

Assessing the extracts properties.

Besides its composition and bioavailability, the value of the seaweed extract as a food ingredient will also depend on how it performs as an ingredient in food manufacture. To address this, the University of Auckland researchers are investigating a range of physico-chemical properties of the extract. “We are excited to be working with this material,” says Dr Siew-Young Quek. “Already we can say that the extract has unique and interesting characteristics that could be desirable as a novel food ingredient,” she adds. The Auckland team is assessing a range of attributes that will be the basis of specification sheets and pointers for particular food applications. Already, the distinctive red pigmentation of the extract and its foaminess, are sparking ideas within the team. “One example of what might be possible is an ingredient providing the red colour for meat substitutes – other possible high-value end uses include novel health-promoting tonics, snack bars, or soup-based products,” says Dr Wheeler. “Further work on the extract’s attributes, including joining forces with consumer perceptions researchers, will reveal the best route to market,” he adds.

Are seaweeds the next superfood?

It is too early to tell from this research. However, the team is taking the first steps to address whether the Pyropia and Porphyra genera of seaweeds confer health benefits beyond nutrition. Through a collaboration with AgResearch they have already shown that the metabolome of karengo species is complex and dynamic, and in two separate collaborations with Malaghan Institute in Wellington and the University of Hokkaido in Japan, the team has discovered that extracts enriched for bioactive metabolites such as polyphenols show both anti-inflammatory and immune-boosting activities in cell culture models. As part of their joint MBIE Catalyst Strategic programme with Singapore, the composition of proteins and polysaccharides in the extracts is being characterised by researchers at the Bioprocessing Technology Institute, one of the A*STAR institutes in Singapore, who are using cutting-edge methods of proteomics and glycomics to establish a link between molecules and health-promoting function in this group of seaweeds. Now the team is about to embark on their most ambitious step, of demonstrating the beneficial effects of digestive function and energy metabolism in people through a clinical trial. “We hope this clinical trial will be the first in a series that will need to be done to provide convincing evidence for the health-promoting effect of karengo,” says Dr Wheeler.