Every kilogram of dried seaweed a buyer receives is part seaweed and part water. The water adds weight but no carrageenan, and too much of it can turn a sound lot mouldy in a warehouse or a container. That is why moisture content is one of the first figures on any seaweed specification, and why it is worth understanding how the number is produced before agreeing to it in a contract.
Why Moisture Matters to Both Sides
Moisture affects three things at once.
- Weight and price. Seaweed is bought and sold by weight. The wetter the lot, the more of the invoice pays for water, and the less material the processor can extract.
- Storage life. Seaweed that is not dry enough can heat up, grow mould and lose quality, particularly in humid tropical warehouses or during long sea voyages.
- Weight loss in transit. A lot that leaves the port wetter than agreed will usually weigh less on arrival as it continues to dry, which leads to disputes about who bears the difference.
Sellers are not always at fault. Dried seaweed is hygroscopic: it picks up moisture from humid air and gives it up again in dry conditions. A lot that was properly dried can still absorb water if it is stored badly or left uncovered. Our article on why drying decides the price explains what happens at the farm end.
How Moisture Is Measured
Three methods are common, and they do not always agree.
Oven drying (the reference method). A weighed sample is cut or ground, dried in a laboratory oven at a set temperature for a set time, or until its weight stops changing, and weighed again. The loss in weight is reported as moisture. This is slow but it is the method most contracts point to when there is a dispute, so the exact temperature, duration and sample preparation should be written into the agreement.
Moisture analysers. These instruments heat a small sample, often with a halogen or infrared lamp, and weigh it continuously. They give a result in minutes and are useful at a warehouse or loading point, but they should be checked regularly against the oven method on the same material.
Hand and eye judgement. Farmers and collectors assess dryness by squeezing a handful, listening to how it rustles and watching how salt crystals form on the surface. This is valuable experience, but it is not a measurement and cannot settle a commercial disagreement.
Whatever the method, the result is only as good as the sample. Moisture varies between sacks and even within a sack, so how samples are drawn matters as much as the test itself.
How Contracts Handle Moisture
A well-drafted seaweed contract usually deals with moisture in a few clear clauses:
- A maximum moisture level, stated as a figure agreed between buyer and seller for that grade.
- The test method, including oven temperature, drying time and sample size, or a named standard.
- Where and when the test counts: at loading, at arrival, or both, and which result prevails if they differ.
- What happens above the limit: a price deduction for each unit of excess moisture, a right to reject the lot beyond a second, higher threshold, or both.
- Who tests: the buyer’s laboratory, the seller’s, or an independent inspection company, and who pays.
Price adjustments are often calculated in proportion to the excess, so that the buyer pays for the seaweed it actually receives rather than for extra water. Some contracts also pair moisture with a yield figure such as clean anhydrous weed, which looks at the dry, clean material directly.
Practical Steps That Reduce Disputes
Buyers and sellers can avoid most moisture arguments by agreeing the method before the first shipment, keeping sealed reference samples from each lot, storing sacks off the floor in a dry, ventilated space and recording moisture at each handover. A good warehouse with documented storage conditions helps both sides trust the figures.
Frequently asked questions
Why does my arrival moisture differ from the loading certificate?
Seaweed keeps exchanging moisture with the air during storage and transport, and the two tests may have used different samples or methods. Agreeing which test prevails, and using the same method at both ends, reduces the gap.
Is lower moisture always better?
Within reason. Seaweed that is dry enough to store safely is what buyers want; beyond that, extra drying time in the sun can affect quality in other ways. The right target depends on the grade and the processor’s needs.
Can moisture be tested at the farm?
Portable analysers make it possible, and they help farmer groups sell seaweed that already meets the buyer’s limit. They should still be checked against a laboratory reference.
Working with Kospermindo
Kospermindo works with farmer groups in South and Central Sulawesi through Farmer Group Centres that offer mentoring and technical assistance, and it has a warehouse in the Makassar Industrial Estate. Read about partnering with us or get in touch.