Solar-tent dried usipa, utaka and ndunduma

Three small fish from one lake

The usipa is a small, thin freshwater sardine, and the Slow Food Ark of Taste counts it among the non-cichlid fish endemic to Lake Malawi. Its scientific name is Engraulicypris sardella, a cyprinid, and it is not the same fish as the Tanganyika sardines sold under similar names. Wikipedia’s usipa article calls it a small sardine-like fish that occurs in large shoals, and it is also known as the Lake Malawi sardine.

The utaka and the ndunduma are different. Utaka is a group of Copadichromis cichlids, and the solar-tent study worked on Copadichromis virginalis from the Cape Maclear landing sites in the south of the lake. Ndunduma is a Diplotaxodon cichlid. Those fish are dried alongside usipa, but they belong to different genera and each needs its own record. A market name such as ndunduma tells you a group of fish, not one identified species.

Why the fish were dried in the first place

The Ark of Taste reports that fishermen work at night with torches, because the fish gather around light. The fish are then sun-dried, half-boiled and dried, or cooked fresh, and dried usipa is sold at most Malawian markets. The Ark entry names mululi for sun-dried fish and wakufwafwaska or wofutsa for the half-boiled and dried form.

The problem is the weather. The IDRC project describes peak catches coinciding with rainy, humid seasons that hamper drying and smoking, and it reports that more than 40 per cent of the catch was lost during processing. An Al Jazeera report from 2016 gives a similar picture: fish dried in the open on wire racks, spoiled in the rainy season before they were properly dried, and were exposed to dust and flies. One processor quoted there said open drying exposes fish to dust, house flies and poor sanitation.

How the solar tent works

The tent is a polythene enclosure over a frame. The IDRC project used 200-micrometre, UV-treated polythene stretched over a wooden frame. Inlet vents sit low on both sides and outlet vents high, so air moves through by convection and carries moisture out. The fish lie on racks inside the tent. The purpose of the design, in the project’s words, is continuous airflow and protection from rain, dust and animals.

The study on utaka describes the tested unit as 12 m long, 5 m wide and 5.5 m high at the centre, with racks 11 m by 1 m and 90 cm gaps between them. The inlets measured 30 by 30 cm and the outlets 40 by 40 cm. Those are the dimensions of the research installation. The sources do not offer a design for a household tent. A sealed box that gets hot is not the same thing: the outlet has to let moist air leave.

What the drying changed

The two laboratory studies are consistent on the main points. In the utaka study, solar-tent fish held about 7.2 per cent moisture against 16.3 per cent for open sun-dried fish, with ash at 14.5 against 22.0 per cent. Protein (about 63 per cent) and fat (about 23 per cent) were similar in both. The usipa study reports 6.3 against 15.5 per cent moisture. Protein and fat again did not differ significantly between the methods.

Microbial counts moved the most. The utaka study reports total viable counts of 2.2 x 10^2 CFU/g in tent-dried fish against 4.1 x 10^5 CFU/g in open sun-dried fish, and the authors report no E. coli, Salmonella or Shigella in the tent product. The usipa study reports 2.5 x 10^2 against 4.1 x 10^5, with Staphylococcus and Vibrio also far higher in the open product. Both papers attribute the difference to lower moisture limiting microbial growth. The published figures conflict in places: the abstracts and results sections of the utaka paper give different coliform and Shigella counts, and the sample sizes and replicate runs are not reported. Read the counts as a direction, not as a measured safety margin.

Consumers preferred the tent product in the utaka study. On a five-point scale, overall acceptability was 3.8 for solar-tent fish and 2.2 for open sun-dried fish, with appearance, colour and smell all higher for the tent product. That is a small panel of ten adult volunteers, and it measures liking, not safety.

Losses, markets and who dries

The IDRC project reports that total value-chain loss fell to 22.25 per cent, against 30 to 40 per cent with traditional methods. At the processing stage alone, loss was 0.8 per cent in the tents and 11.3 per cent in open-air sun drying. The project estimated an 80 per cent probability that the dryers would be profitable. Those figures come from the project’s own accounting and differ between the project summary and other summaries, so they should be read as reported rather than audited.

The project reports about 86,685.5 kg dried in its programme, worth more than US$540,000, and more than 10 formal markets opened to processors. It says 188 people, 123 of them women, were using solar tents by the end, against none at the start, and that women received about double the price in the formal markets. Malawi’s Ministry of Agriculture promotes the dryers as climate-smart technology under the name Samva Nyengo, and the Fisheries Department has recommended extending solar tents to other water bodies. Al Jazeera’s 2016 report estimated that dried fish contributes about 4 per cent of Malawi’s GDP and that the industry employs more than 50,000 fishermen.

Eating the dried fish

Dried usipa is usually eaten whole, bones included, because the bones are soft after drying. Wikipedia’s usipa article says it is usually eaten with nsima or ugali, the maize porridge that is the staple of the region. The Ark of Taste describes fresh usipa cooked and served with nsima or with rice, and the half-boiled, dried product (wakufwafwaska or wofutsa) is a second traditional route.

No separate dish is recorded for dried utaka or ndunduma. Appearance, smell and taste do not establish safety, and the solar-tent studies measured bacterial differences that a cook cannot see.

Limits and unknowns

No source gives a drying time for the tent in hours or days that a processor can plan against, a moisture target, a loading density, or a rule for when a batch is dry enough. The utaka study does not state its drying durations. The sources do not give the household cost of a tent, and the Ark of Taste names definite overfishing of usipa with no fishing rules in place.

The fish should not be treated as one food. Usipa, utaka and ndunduma differ in species, size and flesh, and the solar-tent work on each is a separate study. Any drying table should record which fish it used. This page keeps the process and the figures attached to the study that reported them.