Rockweed soup? How researchers are trying to boost use of native seaweeds

Slimy, salty, fishy, sour and bitter.

That's how non-consumers of seaweed often describe what they think seaweed will taste like.

"Not … things you really want to hear about a food ingredient," says Matt McSweeney, a professor at Acadia University's school of nutrition and dietetics.

McSweeney and other researchers at Acadia are hoping to change that perception by figuring out what people think of seaweed after they try it in food, and, ultimately, how to improve the taste experience.

A key ingredient in the study? Vegetable soup.

Soup study

McSweeney and two undergraduate students, Allison Stright and Kaitlyn Frampton, served vegetable soup with seaweed powder in it to 103 people who were not regular consumers of seaweed.

The taste testers tried soup with a sprinkling of either Irish moss or rockweed in two different quantities — 1.5 per cent and three per cent by weight — or what amounted to a small "sprinkling" or two of powder mixed into the bowl, McSweeney says.

They were asked to evaluate how they liked the flavour, appearance and mouthfeel of the soup, as well as the intensity of saltiness, sourness, bitterness, sweetness and umami. Umami is a savoury, rich taste associated with meat, fish, mushroom and ripe tomatoes.

Their study, published recently in the Journal of Sensory Studies, found that while the seaweeds increased the umami and saltiness of the soup, they also increased the bitterness and sourness. The Irish moss decreased enjoyment of the flavour of the soup with both the lower and higher amounts of seaweed, while the rockweed only decreased liking at the higher level.

McSweeney says since seaweed is an "underutilized ingredient" in the Western world, there's a bit of an uphill battle to develop the market for it in food products.

"We think about consumers, they are familiar with certain flavours and textures, and when you push them past flavours and textures they're familiar with, that usually leads to disliking."

People, planet, profit

But increasing the consumption of Irish moss and rockweed in food in Nova Scotia could have benefits, McSweeney says.

"It basically fits what we called the three Ps of sustainability — people, planet and profit. So it's going to benefit people because it's good for them. It's going to benefit the planet because it's environmentally friendly and, you know, also hopefully we can make a little money if we harvest it and put it in foods that are acceptable to people."

Seaweed is nutrient-dense, rich in minerals and low in fat, and some researchers have suggested its saltiness can be used to reduce the amount of salt added to foods.

Market potential

Seaweed is also big business, with the potential to grow, says Shannon Arnold, the associate director of marine programs at the Ecology Action Centre.

Arnold and her colleagues have been working on promoting both the production and consumption of seaweed — particularly kelp. According to a report released in 2023, the kelp industry alone in North America is worth about $200 million, and Nova Scotia's portion of that kelp market could grow to $38 million in the next few years. 

Arnold says food product developers have created crackers, bread, caviar, pickled salad and "Kelp-mato" (instead of Clamato) using kelp, and 26 restaurants in Halifax have kelp on their menu.

While Irish moss and rockweed have not traditionally been a headlining ingredient in food, Arnold says consumers eat it all the time without necessarily knowing.

Rockweed and Irish moss have long been used as thickening or gelling agents under the name carageenan.

"If you go to the grocery store, you can fill up a basket right away with an ingredient list that has carageenan at the bottom of it.… It's in tons of dairy products, it's in deli meat, it's in toothpaste, it's in things that need to be emulsified."

Acadian Seaplants, a Nova Scotia seaweed business, has developed a food product called Hana Tsunomata using land-cultivated seaweed that originally came from Irish moss. Arnold says that product is largely exported to Japan. Acadian Seaplants did not respond to an interview request about their product.

For McSweeney, the challenge now is to minimize the "off-flavours" such as sourness or bitterness, and figure out what food products consumers find Irish moss and rockweed acceptable in.

"I think that people are open to trying seaweed in food right now, like, they're quite positive about it. They want to try it."