Once the harvested biomass is brought to shore, a process has to be applied quickly due to the high water content of most species.This step is not always carried out by the farmers and the level of sophistication varies between seaweed species and its designated application.The processing conversion factor is an important measure to take into account when evaluating crop and the processing yield.
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Processing of Undaria involves the separation of the stems, leaves and sporophyll (the root-like part above the holdfast often called Mekabu). The product variety of Undaria is large and ranges from a combination of fresh, blanched, salted, dehydrated or dried processing.
Most of the processing technologies were developed in Japan, yet nowadays processing methods are fairly similar across producing countries and regions. The capacity and sophistication (automation) of the processing line varies significantly across companies.
Processing conversion ratios, like the wet-to-dry ratio, can vary across harvests, regions and due to nuances in processing.
In South Korea, about 60% of the harvested Undaria is fed directly to abalone on neighbouring farms. The remaining harvest is mainly processed into blanched, salted or dried products. Drying is often a bottleneck for the farmer since it is space and weather dependent if done outdoors, or energy intensive and expensive if done indoors.
In the highest producing region of Japan, Sanriku, around 60% of the processing is done by farmers in small-scale facilities, with the capacity to process between 0.5 and 1 tonne of fresh Undaria per day. The remaining 40% of processing takes place in large scale facilities, from fishery cooperatives or companies, that can process up to 50 tonnes per day. The processing period is limited by the auction schedule until the end of April
In China, harvested Undaria is also mainly processed into blanched and salted products. Other processed products include dried leaves, salted dehydrated leaves and stems. Under normal circumstances, 6.5 – 7 tonnes of fresh Undaria produces 1 tonne of salted dehydrated leaves and about 5 tonnes of salted dehydrated leaves can turn into 1 tonne of dried Undaria.