So What’s in My Kelp Anyways?
A deeper dive into kelp composition
It’s a simple question which deserves a simple answer. But as with most things, the actual answer is that it depends!
The first consideration is your use case: what are you trying to use your kelp for? Having a hypothesis helps narrow down the set of relevant tests and can save you a lot of time, effort, and money.
For example, if you’re making a food product, you’ll be more interested in the nutritional and safety aspects of the seaweed. If you’re making a cosmetic or nutraceutical product, the bioactive properties will be more important to you.
But no matter what you’re trying to make, it helps to have a general understanding of seaweed composition.
Making Algae Testing Super Simple
When we started Macro Oceans, one of the challenges we faced was getting high quality, cost-effective, and rapid analysis of our seaweed. If you are facing the same problem, we’ve got your covered!
We partnered with Cultured Supply to set up a one-stop-shop for product developers, farmers, and cultivators to assess the quality of their algae. There are packages for product safety, nutrition, and bioactivity that we run together with lab partners Celignis and Eurofins.
To find out more visit: https://algae.culturedsupply.com/testing
The Basics (from a food perspective)
Like land-based crops, seaweed has five major components:
Moisture: literally the amount of water inside the seaweed
Fats: lipids, fatty acids, etc
Proteins: made up of amino acids, the building blocks of life
Carbohydrates: commonly called sugars
Ash: a fancy catch all for minerals and metals
Obviously there’s a lot of variation between species as well as across locations, growing environments and years for any given species. But if we keep things simple and zoom in on Alaska sugar kelp, this is roughly what you get:
Let’s look at each component in turn.
Moisture
The most important thing to know is that the moisture content in seaweed is high, ranging from ~60% in red seaweeds to 85-90% in brown seaweeds. This means that if you have 1kg of sugar kelp (Saccharina latissima), then you have ~100g of materials to work with, 900g of water. Yep, it’s a lot of water.
The high moisture content has a range of implications. First, as soon as you harvest your seaweed, you have to quickly do something with it because with that much water it will spoil within just a few days. In that sense, it’s not so different from fish or other fresh produce. That’s why people immediately dry, freeze, ferment or stabilize their crop after harvest.
When thinking about composition and what you have to work with, we always talk numbers on a dry weight basis. For example, when we say protein is 10%, we mean it’s 10% of the dry seaweed. Why do we do this? Because the moisture content is a large fraction of the total and it can vary significantly from sample to sample, thus not controlling for moisture can distort measurements significantly.
From here on out, all the numbers are on a dry weight basis …
Fats & Proteins
In general, kelps are skinny, protein deficient plants. Fat content in most brown seaweed is around ~5-7% and protein is not much higher at 8-10%. Of course, there’s some variation by year, geography and species. But overall, it’s best to think of seaweed as a carbohydrate crop.
Having said that, seaweed proteins are intriguing. A meta review of recent studies shows that they have high proportions of all 9 essential amino acids. And dulse (Palmaria palmata) even has a comparable protein profile to an egg!
But remember, if your seaweed has 10% protein on a dry basis then in 1 kg of wet seaweed there’s just 10g of theoretically recoverable protein … So, if you want to sell 10x 55 lb bags of protein powder … you get the idea!
Carbohydrates
There are two main types of carbohydrates in brown seaweeds: polysaccharides and alginates. These are commonly known as complex carbohydrates which are made up of more simple molecules. There are also simple sugars like mannitol which is a sugar alcohol. Let’s look at each type.
Polysaccharides: brown seaweeds are prized for two specific bioactive polysaccharides - fucoidan and laminarin. Fucoidan is a long-chain sulfated polysaccharide with a complex branching structure. This just means that there is a chain of fucose molecules linked together with sulfate groups hanging off of them! Laminarin, is a type of beta-glucan, essentially a co-polymer made up of glucose and mannose molecules. The bioactivity of these compounds has been studied in a range of applications from gut health to skin care to therapeutics. If you want to find out more about how to harness these amazing bioactive compounds in your skincare or haircare product, drop us a line!
Alginates: the other major carbohydrate component of brown seaweed are alginates. Alginates are a type of hydrocolloid, sitting alongside their more famous cousins, carrageenan and agar. They are co-polymers made up of specific types of uronic acids joined together in a linear form (e.g. not branching!). Most commonly you find blocks of mannuronic and guluronic acids connected together. The sequence and proportion of the M and G blocks defines the so-called M:G ratio as well as functional properties like viscosity, gel strength, and cross-linking performance.
One important thing to note: some techniques for measuring these complex carbohydrates are indirect, which means that you don’t measure the complex compound itself, but rather the constituent parts. For example, rather than measuring fucoidan (the polysaccharide) you measure fucose (the monosaccharide). Why do this? Primarily because getting an accurate measurement requires harsher extraction methods which break the complex compounds down into their smallest parts. Once you have your measurement you just need to do a little bit of math to estimate the target compound.
There are many other nuances to carbohydrate measurement in seaweed such as purity, molecular weight, functional performance and more. But I promised to keep it simple so …
Ash
The final component is ash, the panoply of minerals and metals. Measuring the total number is pretty easy - just heat a sample in a muffle furnace to 500c and see how much “ash” is left over. Essentially you’re burning off all the organic material to reveal the non-organic content. Of course, this doesn’t tell you what minerals or metals are actually in your ash - for that you have to do some fancier measurements like ICP-MS.
Understanding the ash content will tell you what sort of micronutrients might be available in your seaweed - important if you were making a biostimulant or an animal feed. It will also help you understand your iodine levels and whether you have any heavy metals - both important for food customers.
Oh, and what about everything else?
Beside the main components of seaweed there are literally dozens of other things you can measure, from vitamins to pigments to phlorotannins. All of these require specialized (and relatively expensive) tests. We’ve run a number of these for clients, so reach out if you want to learn more.