Buyers pay for seaweed, not for what comes with it. Yet a sack of dried seaweed can also contain salt crystals, sand, fragments of rope and plastic, other seaweed species and, in the worst cases, mould. Each of these adds weight without adding value, and most of them begin in a few specific moments between harvest and packing. Knowing where defects come from is the quickest way to judge whether a supplier can control them.
The usual defects and where they start
- Excess salt. Source: seawater left on the seaweed dries into a white crust. Prevention: proper draining, and in some supply chains rinsing, before drying; not adding seawater to gain weight.
- Sand and stones. Source: drying directly on beaches or bare ground, or from off-bottom farms in sandy areas. Prevention: raised racks or platforms, tarpaulins or nets under the seaweed, shaking before packing.
- Rope, raffia and plastic. Source: ties and line fragments left on harvested seaweed, and waste around drying areas. Prevention: careful removal of ties at harvest and tidy drying sites.
- Other seaweeds and marine debris. Source: epiphytes and weeds growing on the crop, or mixed species on the same lines. Prevention: cleaning lines, sorting before drying.
- Mould and discolouration. Source: seaweed packed or stored before it is fully dry, or rewetted by rain. Prevention: complete drying, dry storage, protection from rain.
- Old or diseased material. Source: harvesting too late, or crops affected by ice-ice. Prevention: timely harvest and good farm management.
Drying is the stage where most of these defects either enter or are kept out, which is why we argue that drying decides the price of dried seaweed.
Why the defects matter commercially
Salt, sand and foreign matter are all counted against the lot in one way or another. They reduce clean anhydrous weed — the usable share of the lot, explained in our article on CAW — and they create extra work and wear in processing plants. Salt also attracts moisture, so a salty lot is harder to keep dry in storage and transit. Mould is more serious still: it can make a lot unsuitable for food-grade processing altogether.
How defects are checked
- Visual inspection at collection. Opening sacks and looking for sand, crust, debris and mould catches the obvious problems before lots are combined.
- Representative sampling. Samples drawn from many sacks, not the top of one, as set out in sampling a seaweed lot.
- Hand sorting of a weighed sample. Separating foreign matter and weighing it gives an impurity figure.
- Laboratory tests. Moisture, salt or ash and CAW, using the methods named in the contract.
- Comparison with the specification. Results are read against the agreed limits; see reading a specification sheet.
Prevention is cheaper than cleaning
Some cleaning after drying is normal, but it cannot fully fix a lot that was dried on sand or packed damp. The more effective investments are upstream: clean drying surfaces, protection from rain, and payment that rewards cleaner seaweed so farmers have a reason to take the extra care. Where drying infrastructure improves — covered or raised drying that keeps seaweed off the ground and out of the rain — many of these defects shrink together.
Frequently asked questions
Is some salt on dried seaweed normal?
Yes. Seaweed grows in seawater and some salt remains after sun-drying. The problem is excess salt, which is why specifications set limits and why deliberately adding salt water is treated as adulteration.
Can a buyer tell a salty lot by looking?
Heavy salt often shows as a white crust, but appearance is not reliable enough on its own. Laboratory tests on a representative sample give the real figure.
Does washing seaweed before drying affect quality?
Rinsing can reduce surface salt and sand, but practices vary and handling affects the product. Buyers and suppliers should agree what post-harvest handling is expected rather than assume.
Working with Kospermindo
In 2026 Kospermindo signed a cooperation agreement as a winner of the Madaya Sustainable Fund for a UV-plastic smart drying house programme. Read about the agreement.