How to make dried fish do an about turn!

In a recent project conducted on request by a client, we needed to dry fish using a rather simple traditional method in terms of the ingredients used for the drying process. The project deliverable itself i.e. a validated and optimised version of a traditional drying process, was to be used for allowing subsistence fishermen to add value to very low value catch. In a similar vein the method would also be employed by fisher folk with small quotas using the smaller harbours around the coast. The intended market is the local, and growing, immigrant population as well as a continental export market where a palate for such dried fish species exists. Local consumption also targets the training of local palates in order to enlarge the market for this high-value protein source.

There are many artisanal methods for drying fish, from the very simple (on slabs or hanging) to the more complex (solar and/or electrically heated dryers) with appropriate packing and storage facilities. The drying process validated in this study itself involves filleting and stacking fish while treating each layer with salt and ascorbic acid in a very specific optimised ratio. Originally, this was done by artisanal fisher folk stacking the fish on a pallet, wrapping it in plastic netting and allowing it to dry for one week, after which it is inverted and allowed to dry for a further three weeks prior to moving to the intended market. One problem attached to this is the fact that this very often is done in remote areas or in situations where access to mechanical assistance and/or electricity is not available. The turning process involved is thus a manual one involving appropriate muscle power depending on the mass being dried.

The Agrifood Technology Station, with the contracted assistance of the Product Development Station at the Central University of Technology, designed and built a prototype fish-drying frame and bin that allowed for the drying of approximately 100kg of fish. The unique point of the design was that, based on the frame structure, it could be more easily rolled over to invert the mass of fish to allow for the second phase of drying. At this point the frame can be removed and a new drying process started with fresh fish. The photograph below shows the design element referred to in the frame:

Rotomould box

A plastic roto-moulded box, to contain the drying fish, is then placed in the frame:

Bin in rotomould box

It is envisaged that the material for building the frame, presently galvanised steel, could be replaced by plastic (lighter) and could thus also allow for bigger volumes/masses of fish to be dried in this manner. Furthermore, a mechanical press could be introduced into the design to further compact the drying fish as it loses water. The client, who contractually has first rights to manufacture such units under licence from CPUT, intends rolling out this drying process and its framed bins, in both local coastal communities as well as to inland freshwater fishing communities. It is envisaged that this would lead to employment opportunities for such communities and also to value adding to sometimes poor catch species with little or no street value.

The CPUT intellectual property for this resides under the name Luckyfish Bin.

Larry Dolley
Station Manager
See our sister blog: www.cput.ac.za/blogs/foodtech