POST-HARVEST HANDLING OF KAPENTA (Limnothrissa miodon)
AT LAKE KARIBA, ZIMBABWE

by

S.E. Mutsekwa (Miss)
Division of Aquatic Ecology
Department of National Parks and Wildlife Management
Zimbabwe

1. INTRODUCTION

The role of the kapenta industry in providing fish proteins for the urban - low income and rural populace of Zimbabwe is unequalled by any other fish production system in the whole country. About 20 000 t of kapenta are produced annually from the Zimbabwean side of Lake Kariba. Most of it is salted, sun-dried, and marketed in various size plastic packs. In this state it can reach even the most isolated parts of the country in a good state.

The research done at Lake Kariba Fisheries Research Institute has been mainly on the increased yield and sustainability of the kapenta fishery in the lake. While this will enable the country to benefit more from the fishery, there is also a need to ensure that most of this harvested product reaches the consumer and in an acceptable state; a solution must be found to avoid heavy post-harvest losses and deterioration. Ensuring minimal losses during storage and handling will mean that this valuable product reaches the people who need it most.

In order to evaluate the situation of the kapenta industry a brief survey of the Kariba-based companies was carried out; and a total of thirteen companies were interviewed. The questions asked in the interviews are shown in the annex to this paper. The main objective of the interviews was to establish an inside knowledge of how these kapenta companies operate and the success and problems they have. The interviews also sought to establish the loopholes in the processing procedure that would compromise the health of the consumer. This report is based on the findings of these interviews. The various stages in the processing procedure are detailed below.

2. IN THE LAKE AT NIGHT

The fishing rigs go out in the lake late in the afternoon and are ready to start fishing when it becomes dark. As soon as the kapenta are brought out of the water after each haul they are put directly into empty milk baskets (each holds about 30 kg of fresh kapenta), where they are immediately salted/iced depending on whether the company sells its product dried or frozen. The salting/icing arrests further bacteriological deterioration which is likely to be very high considering the temperatures at kariba which average 27° Celsius and can reach 40°. One of the companies interviewed stated that they sell about 15 % of their product frozen and the rest is dried. Another company ices all its product as soon as it is caught because it deals in frozen kapenta.

There are variations in salting methods. While some companies used brine to salt their fish, most of them employed the dry salting technique. The former group claimed that brining ensures uniform salting throughout the flesh of each kapenta fish and is thus more effective in arresting bacteriological deterioration. The latter group said they preferred dry salting as it was less damaging to the boats than brining and it also resulted in a less salty product more acceptable to the consumer. Ten companies practised dry salting while two brined their produce.

All companies interviewed stated that there was negligible, if any deterioration, between landing in the boat at night and the time the fish were landed at the fishing base the next morning.

3. AT THE FISHING BASE IN THE MORNING

3.1 Sun-Drying

The night's salted catch is landed at about 08.00 hours. The landed fish are instantly weighed, the fisherman paid and the fish immediately spread out on the drying racks.

Drying takes from 8 to 12 hours depending on the weather. During rainy or very humid days the semi-dried fish are taken indoors or covered with polythene sheeting overnight, and drying resumes the following morning.

3.2 Combined Sun- and Mechanical-Drying

Three of the companies interviewed possessed mechanical driers with capacity ranging from 700 to about 3 000 kg. One company used its neighbour's drier.

The landed kapenta are sun-dried for at least two hours or until they develop a “skin”. The semi-dried kapenta are then loaded into trays which in turn are stacked in the drier. The kapenta driers in Kariba use diesel fuel to provide hot air, which is about 58° Celsius. Under optimal conditions the fish remain in the drier for another 2 hours. After this the kapenta are ready for packaging.

The mechanical driers in Kariba were only used by the large companies which have more than ten fishing units. Such companies resort to mechanical driers because of the limited rack space for their catch. These mechanical driers are also practical during the rainy season when it is not possible to use the drying racks.

3.3 Freezing

The previously iced fish are immediately packed in bags of varying weight, sealed and immediately frozen. All this is done in the shed.

4. PACKAGING

The dried and ready-to-pack product is sieved. This process eliminates broken fish, salt grains, dirt and beetles, before actual packaging.

Eleven of the companies interviewed packed some of their produce in hessian sacks in 30 kg consignments. Some of the produce is packed in polythene packs in 500 g consignments, which were in turn put into 2 kg bales before being packed in hessian or polypropylene bags. These packed products are then ready for storage in the warehouse or sale to the wholesaler, shop owner or in some cases to housewives.

5. STORAGE - WAREHOUSE

The packaged products are then stacked in rows in the warehouse with spaces between the rows to facilitate ventilation. The duration of the stay of the product in these warehouses can vary from a few hours to 3 months depending on the size of the daily catch and the market demand.

It is during the stay in these warehouses that the problems of beetle (Dermestes maculatis) infestations occur. Of all the companies that store their dried products in the warehouses, only one of them indicated that they regularly fumigate/spray their stored product with a variety of insecticides (depending on availability). The rest indicated that the beetle infestations normally occurred during the period March/April/May when the temperature is high and the humidity very low. Under these conditions the products may easily over-dry (i.e., above the 3:1 wet:dry ratio), thereby encouraging beetle infestation.

6. COMMENTS

6.1 The practice of salting/icing the kapenta as soon as they are taken out of the water is recommendable and has generally proven to be very effective. Only the big companies however can afford to use the latter method because only they can easily obtain enough ice and also because of the limited distribution of the frozen product; and only they have enough capital to invest in refrigerated trucks. There is also a limit to the amount of frozen product that can be disposed of, as this can only be handled in the urban centres where there are freezing facilities for the frozen product. Even so, some of the frozen kapenta from Kariba has been found as far south as Cape Town (South Africa).

Even though many companies interviewed expressed concern about the cost and irregular supply of salt, and the damage that salting caused to kapenta rigs, they all pointed out that most of the kapenta produced is really meant for the rural population which has no alternative source of protein. These companies rightly felt that it was still necessary to sell most of their produce dry which necessitates the continued use of salt.

Of the two methods of salting, dry-salting appeared more popular, as this seemed to cause less damage to the rig's body work. The companies that practise brining claim that it is the more effective of the two methods. The author observed that the dry salting was good enough and the product was not so salty.

6.2 Sun-drying proved to be the most popular method of processing kapenta. The sun-dried product has a long shelflife (some claimed it could last up to about six months), was cheap and acceptable to the Zimbabwean consumer. The only limitation to this method was in the case of adverse weather conditions. If it rained for more than two days continuously all the companies without mechanical driers stated that they had to stop fishing operations altogether until the rain stopped.

Mechanical drying enables the big companies with limited rack space to handle their large catches with minimal losses. These driers would also be useful during the rainy season. Even so, these companies cut down on their operations when there is continuous rain. This is due to the limited capacities of the driers and also to the fact that when these driers are loaded to capacity they become very inefficient as air circulation is retarded and humidity increases. The wet kapenta also tend to become “cooked” thereby producing a very inferior product which tends to powder during packing and distribution. A 700 kg drier costs about Z$ 30 000. One of the companies stated that their losses during the rainy season were still too low to justify the purchase of a drier. There is obviously a need to improve the technology of the driers.

Smoking was only tried once by one company. The taste of the smoked product proved to be very unpopular to the consumer and the experiment was never repeated. Because of its high fat content kapenta is not good for smoking as it easily becomes rancid.

The canned product too was tried once, was accepted by the consumer, but the cost of the tin made this product so expensive that it was out-competed by the dried product. Perhaps the presentation of this “canned” product in less expensive containers would reduce the costs and at the same time present the consumer with a wider selection.

The frozen product suffers mainly from its limited distribution range. While the predominant complaint was that there was not enough refrigerated transport to cater for it, there is still scope to experiment with insulated containers which keep the frozen product fresh for up to 24 hours by which time it can reach most points of distribution - widening the choice even more for the rural consumer.

6.3 Although beetle infestation did not seem to present an acute problem, the practice of fumigating/spraying with insecticide needs to be constantly monitored. Most companies fumigate their warehouses with phostoxin tablets (i.e., aluminum phosphide) which is comparatively safe. They also limit the use of this fumigant to when the beetles are actually observed. One company confessed to using various brands of insecticide depending on availability and also to using insecticides in the warehouse as a routine.

The same company also admitted that during their 15 years operation they have used over 30 different types of insecticide. They however stated that before they used a new insecticide it had to be tested for at least two years by the Ministry of Health. It is questionable how effective this system of checking is. Such a situation is obviously highly dangerous. It is suggested that government should impose strict regulations on the sale of insecticides for use by any food industry to protect the health of the consumer. In the case of the kapenta industry regular checks should be maintained on any possibility of residues of harmful insecticides on the product. Encouraging the use of insecticides only when necessary will also reduce the chances of insecticide contamination. Two of the companies interviewed stated that they found that the use of polypropylene bags instead of the hessian ones eliminated the occurrence of the beetles and they therefore hardly ever used any insecticide at all.

7. ACKNOWLEDGMENTS

The author offers sincere thanks to the Officer-in-Charge (Lake Kariba Fisheries Research Institute) for allowing this survey to be carried out and to the Institute for bearing the costs. Thanks are also due to Mr Magarangoma and Mrs Gapara for driving her to the various fishing companies. The under-mentioned Companies were most useful in providing the information presented in this report.

Annex

QUESTIONS PRESENTED IN THE INTERVIEWS

• Name of company/cooperative?

• Number of units possessed?

• Average catch per unit per night?

• What happens to the fish as soon as they are brought out of the water?

• Do you experience any deterioration before the fish are landed at the fishing base?

• Is this method of processing very effective in reducing deterioration? Do you sometimes encounter problems with this method? If yes, what are they?

• On average how long do you keep the processed product before it is sold?

• Do you experience any losses during this transition period? If yes what is the percentage of total production?

• What is the shelflife of your processed product?

• Who to you sell your product to?

• Would you wish to use alternative methods for processing your fish? If yes what limitations do you face?