International Journal of Aquaculture, 2016, Vol.6, No.18, 1
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many developing countries (Kumolu-Johnson et al., 2010). Smoke preserves and increases shelf life of fish by
drying, cooking, acting as an effective antioxidant, bacteriostatic and bactericidal agent (Rorvik, 2000; Ahmed et
al., 2010; Daramola et al., 2013). Salting is usually used in combination with drying and smoking to remove water
and lower the water activity through osmosis (Abbas Bakhiet and Khogalie, 2012).
Different processing methods have different effects on nutritional composition of fish (Eves and Brown, 1993).
Studies have demonstrated that processing alter nutrient content of the processed fish products (Ahmed et al.,
2011; Oparaku and Mgbenka, 2012; Makawa et al., 2014). The need to determine nutrient content of processed
fish is therefore indispensable to ably inform consumers about nutritional composition of the processed fish which
they buy on the markets. The objective of this study was to determine the effect of processing methods on the
quality of fresh fillets of
Rhamphochromis
species (Mcheni) from Lake Malawi, Malawi.
2 Materials and Methods
2.1 Fish sample collection
A total of 1,080 fresh
Rhamphochromis
fish samples (individual weight ±300 g) (Figure 1) were collected (bought
from fishers early in the morning) from the South-East Arm of Lake Malawi in Mangochi District, Malawi.
Samples were quickly packed in plastic bags, and preserved in block ice then transported to the laboratory for
analysis.
Figure 1 Freshly caught
Rhamphochromis
species
(Mcheni) from Lake Malawi kept on block ice
2.2 Fish sample preparation and processing
The fish were washed and carefully prepared into fillets using a sharp knife without breaking the muscle (flesh).
The fish fillets were separated into five (5) groups which were i) Sundried, ii) Sundried then smoked, iii) Smoked,
iv) Salted then sundried, v) Salted then smoked. Some fillets were analysed fresh as a control. The trial thus had 6
treatments arranged in a factorial design in triplicate.
In sun drying, cleaned fish were spread over chicken wire on an open drying rack and exposed to the sun for about
4 days. In salting, fillets were immersed into a brine solution of 5% (Sodium chloride) per liter of water for half an
hour while stirring every 15 minutes to achieve an even concentration. Smoking was done in the Ivory-Coast
smoking kiln, a modification of the traditional smoking kiln using dry nuts of palm trees (Figure 2) which are
common among fish processors. The Ivory-Coast kiln is a modification of the traditional smoking kiln which has
demonstrated to produce high quality processed smoked product.
2.3 Proximate analyses
Proximate composition (moisture, protein, fat, ash and energy) was analyzed according to AOAC (2005) standard
procedures. The following formulae were used for calculating respective variables: Dry matter (%DM) = Wt of
sample after drying / Wt of sample before drying x 100. Moisture content (%) = 100 - % DM. Protein (%) = {0.01
x 14.007 x titration volume x 6.25 x (200/ 5) x 100}/ Wt. sample x 100. Crude fat (ether extract) (%) = (Wt of
