Research Report

Effect of Sun-drying, Smoking and Salting on Proximate Composition of Fresh Fillets of Mcheni (Rhamphochromis species - Pisces: Cichlidae) from Lake Malawi, Malawi  

Nevarson C.J. Msusa1 , Fanuel Kapute2 , Jeremy S. Likongwe3 , Daniel C. Sikawa3 , Austin H. Mtethiwa3
1 Ministry of Agriculture and Food Security, Department of Fisheries, Malawi College of Fisheries, Private Bag 7, Mangochi, Malawi
2 Mzuzu University, Faculty of Environmental Sciences, Department of Fisheries Science, P/Bag 201, Luwinga, Mzuzu 2, Malawi
3 Lilongwe University of Agriculture and Natural Resources, Bunda College, Faculty of Natural Resources and Environmental Management, Department of Aquaculture and Fisheries Science, P.O. Box 219, Lilongwe, Malawi
Author    Correspondence author
International Journal of Aquaculture, 2016, Vol. 6, No. 18   doi: 10.5376/ija.2016.06.0018
Received: 13 May, 2016    Accepted: 11 Jul., 2016    Published: 20 Oct., 2016
© 2016 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:

Msusa N.C.J., Kapute F., Likongwe J.S., Sikawa D.C., and Mtethiwa A.H., 2016, Effect of sun-drying, smoking and salting on proximate composition of fresh fillets of Mcheni (Rhamphochromis species - Pisces: Cichlidae) from Lake Malawi, Malawi, International Journal of Aquaculture, 6(18): 1-5 (doi: 10.5376/ija.2016.06.0018)

Abstract

A study was conducted to determine effect of sun-drying, smoking and salting on proximate composition of fresh fillets of Rhamphochromis species fish (local name: Mcheni) from Lake Malawi, Malawi. Fresh fillets prepared from the fish were sun dried, sun dried then smoked, smoked fresh, salted then sun dried, and salted then smoked. The processed fillets were then analysed for proximate composition. Highest and lowest moisture content was observed in fish that were salted then smoked (28.99±0.02) and sundried then smoked (8.56±0.51) (P<0.05). Sundried and salted then smoked fish had the highest and lowest protein (53.68±0.79, 32.53±0.17) and energy (24.00±0.05, 16.31±0.02) levels respectively (P<0.05). More fats were retained in sundried fish (27.25±0.02) while fish that were salted then sundried had the lowest fat content (11.09±0.05) (P<0.05). Salted then sundried fish had more ash (18.83±0.12) while lowest ash levels were observed in fish that were smoked (5.03±0.03). A general observation was that sundried fillets had higher protein, fat and energy content while smoking significantly reduced nutrient levels. On the other hand, salting increased ash levels in the fillets and a combination of sun drying and smoking helped to produce a product with very little moisture content. Results suggest that consumers would have a more nutritive product by avoiding adding salt to Rhamphochromis fillets but rather sun drying and smoking. The lowest moisture content in sundried and smoked fillets also suggest a processed product with a longer shelf life as moisture favours microbial growth that are responsible for most spoilage in fresh foods.

Keywords
Rhamphochromis species; Fillets; Smoking; Salting; Proximate Composition

1 Introduction

Fish is a good and highly nutritious food among many reasons, its high quality proteins, vitamins and minerals (Ojutiku et al., 2009). In Malawi, fish provides the most affordable source of the much needed animal protein because it is widely distributed and presented in forms that even low income people can afford. Fish is nevertheless highly perishable due to complex processes involving physical, chemical and microbiological activities (Sallam, 2007; Ojutiku et al., 2009). Rhamphochromis species are a high commercial value predatory fish usually caught by hand lining. It is generally considered as fatty compared to other fish species endemic to Lake Malawi such as Tilapia hence spoils fast due to fat oxidation. The need to preserve and/or process fish soon after capture is mandatory in order to prolong its shelf life. The commonest processing methods for fish in Malawi are sun drying and smoking. A considerable portion of fresh fish is also salted especially gutted larger sized fish that are later sun dried or smoked.

 

Drying involves the application of heat to remove moisture from a product hence preserves fresh fish by inactivating enzymes and removing moisture necessary for bacterial and mould growth (Duan et al., 2004). This explains why dried products exhibit a longer shelf life, enhance quality and provide ease of handling (Mujumdar, 2007). Smoking is probably one of the oldest and commonest methods of fish preservation and processing in 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.

 

Figure 2 Dried Palm tree nuts used for smoking the Rhamphochromis fish fillets

 

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 crude fat / Wt of sample used) x 100). Energy (J/g) = (sample joules x 1) / sample wt. Ash (%) = (Wt. of ash / Wt. of original sample) x 100.

 

2.4 Data analysis

All statistical analyses were conducted using Microsoft Office Excel for Windows 2003. Treatment means were compared using Analysis of Variance (ANOVA) at 5% level of significance in SPSS for Windows statistical software version 15.0. Significant mean differences were separated using Duncans Multiple Range Test (DMRT) and results reported in mean standard error (±SE).

 

3 Results and Discussion

Results for proximate composition (moisture, protein, fat, ash and energy) of the Rhamphochromis fresh fillets are presented in Table 1. Highest and lowest moisture content was observed in fish that were salted then smoked (28.99±0.02) and sundried then smoked (8.56±0.51) (P<0.05). Fish that were sundried and salted then smoked exhibited the highest and lowest protein (53.68±0.79, 32.53±0.17) and energy I24.00±0.05, 16.31±0.02) levels respectively (P<0.05). More fats were retained in sundried fish (27.25±0.02) while fish that were salted then sundried had the lowest fat content (11.09±0.05) (P<0.05). Salted then sundried fish had more ash (18.83±0.12) and lowest ash observed in fish that were smoked (5.03±0.03). A general observation was that fillets that were sundried had better protein, fat and energy content while smoking of the product resulted into lowest levels of these nutrients. On the other hand, salting increased ash levels in the fillets and a combination of sun drying and smoking helped to produce a product with very little moisture content.

 

Table 1 Proximate composition of fresh Rhamphochromis fish fillets processed with different methods

Means with the same superscript in a column are significantly not different (P>0.05)

 

Results agree with several earlier studies suggesting that processing alter nutrient content of food products (Eves and Brown, 1993; Ahmed et al., 2011; Oparaku and Mgbenka, 2012; Makawa et al., 2014).

 

3.1 Moisture

The low observed moisture content in this study for sundried and smoked fish has been earlier reported by Sveinsdottir (1998) attributing to the fact that smoking decreases water activity in fish tissue. The high moisture content in fillets that were salted before sun drying or smoking agrees with Bille and Shamkai (2006) who suggested that increase in the moisture content of salted dagga fish samples could be due to the hydroscopic nature of Sodium chloride (NaCl) which takes up moisture from the surrounding environment also reported by Khan and Khan (2001). Other authors (Hernandez-Herrero, 1997; Ahmed et al., 2010; Alsaban et al., 2014) also reported reduced moisture content with salting in fish. Sundried fish would therefore exhibit better storage properties because moisture favours microbial growth.

 

3.2 Protein

Protein decreased with salting in this study earlier reported by Holma and Maalekuu (2013) and Alsaban et al. (2014) while high protein content in sundried and smoked fillets has been observed by Fapohunda and Ogunkoya (2006). It is reported that the level of free amino acids in salted and sun dried fish decrease during storage (Smith and Hole, 1991). High protein content in smoked fillets could be due to concentration of nutrients due to loss of water (Doe and Olley, 1983). It is known that salt alters colloidal properties of the proteins and changes the nature of the water/protein relationship (Alsaban et al., 2014). This is explained by the denaturation of both sacoplasmic and myofibrillar proteins due to the effect heavy salting on fish muscle also reported by Ahmed et al. (2010). This suggests that sundried Rhamphochromis species is the best source of dietary animal protein and that addition of salt though increases shelf life compromises the nutritive value of the fish.

 

3.3 Energy

Results show a correlation between fat, protein and energy values in a way that energy decreased with decrease in fat content since fats are the energy source. It also follows that the higher the protein content, the higher the energy level (Holma and Maalekuu, 2013). The lower moisture content in sundried smoked fillets would mean more lipids and protein and consequently higher energy density in the fish (Aberoumad and Pourshafi, 2010).

 

3.4 Fat

Low fat content in salted fillets could be due to physical losses that are usually necessitated by the breakdown of tissue cells during salting, followed by the heating effect of sun-drying (Pace et al., 1989; Holma and Maalekuu, 2013). According to the Food and Culture Encyclopedia (2003), salted and sun dried fish are also more prone to oxidation than fish preserved by other methods because of their exposure to light and oxygen. The lowest fat content of 11.09% in the salted sundried fillets suggests that Rhamphochromis species are fatty fish because fish are only considered as lean when fat content below 5% (Ackman, 1989). In this study, there was a correlation of high moisture and fat content for salted fillets of which the implication would be a relatively short shelf life of the fillets due to microbial spoilage (high water content) and lipid oxidation.

 

3.5 Ash

Salting increases ash content (Ahmed et al., 2010; Alsaban et al., 2014). The increase in ash content during salting in this study may be due to the effect of extracted lipid which helps to create a crusted surface on each dried fish (Mohammed, 2007). Addition of salt may have added more ash components to the product (Beauchamp and Engelman, 1991). The effect of ground bones and scales in dried fillets could also have resulted into increase in ash content (Alsaban et al., 2014).

 

4 Conclusion & Recommendations

Sundried Rhamphochromis species is rich in protein - the most sought after nutrient in fish but also a fatty fish. Results further suggest that consumers would have a more nutritive product by avoiding adding salt to Rhamphochromis fillets but rather sun drying and smoking. The lowest moisture content in sundried and smoked fillets also suggest a processed product with a longer shelf life as moisture favours microbial growth that are responsible for most spoilage in fresh foods. It was observed that processing method (sun drying then smoking) that increase (concentrate) protein in the fillets also reduced fat content. This is an advantage because a fatty product undergoes rapid spoilage due to lipid dehydrogenation.

 

References

Abbas Bakhiet H.H., and Khogalie F.A.E., 2012, Effect of different salt concentrations on chemical composition of the fish Hydrocynus spp, Online Journal of Animal Feed Research, 2(6): 461-464

 

Aberoumad A., and Pourshafi K., 2010, Chemical and Proximate Composition of Different Fish Species Obtained from Iran. World Journal and Marine Sciences, 2(3): 237-239

 

Ackman R.G., 1989, Nutritional composition of fats in seafoods, Progress in Food Nutrition and Science, 13: 161-241

 

Ahmed E.O., Ali M.E., Kalid R.A., Taha H.M., and Mahammed A.A., 2010, Investigating the quality changes of raw and hot smoked Oreochromis niloticus and Clarias lazera, Pakistan Journal of Nutrition, 9(5):481-484

http://dx.doi.org/10.3923/pjn.2010.481.484

 

Ahmed A., Ahmadou D., and Mohamadou B.A., 2011, Influence of Traditional Drying and Smoke-Drying on the Quality of Three Fish Species (Tilapia nilotica, Silurus glanis and Arius parkii) from Lagdo Lake, Cameroon. Journal of Animal and Veterinary Advances, 10: 301-306

http://dx.doi.org/10.3923/javaa.2011.301.306

 

Alsaban W.A., Abou-El-Hawa S.H., Hassan M.A.M., and Abdel-Rahman M.A., 2014, Effect of salting and storage on chemical composition of some fish species, Journal of Food and Dairy Science, 5(6): 451-458

 

Association of Official Analytical Chemists (A.O.A.C), 2005, Methods of Analysis, 17th edition Washington D.C, USA

 

Beauchamp G.K., and Engelman K., 1991, High salt intake, Sensory and behavioral factors: Hypertension, 17(1S): I176-81

http://dx.doi.org/10.1161/01.HYP.17.1_Suppl.I176

 

Bille P.G. and Shemkai R.H., 2006, Process development, nutrition and sensory characteristics of spiced-smoked and sun-dried dagaa (Rastrineobola argentea) from Lake Victoria, Tanzania, African Journal of Food, Agriculture, Nutrition and Development, 6(2): 1-12

 

Daramola J.A., Kester C.T., and Allo O.O., 2013, Biochemical changes of hot smoked African catfish (Clarias gariepinus) Samples from sango and Ota Markets in Ogun State, The Pacific Journal of Science and Technology, 14 (1): 380-386

 

Doe P.E. and Olley J., 1983, Drying and dried fish product, In the Production and Storage of dried fish, FAO Fish Report, 279: 56-62

 

Duan Z.H., Zhang M., and Tang J., 2004, Thin layer hot-air drying of bighead carp. Fisheries Science, 23(3): 29–32

 

Eves A., and Brown R., 1993, The effect of traditional drying processes on the nutritional values of fish, Journal of Tropical Science, 33: 183-189

 

Fapohunda O.O. and Ogunkoya M., 2006, Effect of smoke-drying on the proximate composition of Tilapia zillii, Parachanna obscura and Clarias gariepinus obtained from Akure, Ondo-State, Nigeria. Animal Research International, 3(2): 478-480

 

Food and Culture Encyclopedia, 2003, Salted Fish. Gale Group Inc. Answers.com, (12/08/09)

 

Hernandez-Herrero M.M., 1997, Influencia de la calidad higienicadel boqueron (“Engraulis encrasicholus var. Mediterraneas”), Thesis Doctoral Universitat Autonona de Barcelona, Barcelona, Spain, (C.F. Awad, A.A.M. (1999): Physical and chemical studies on some factors affecting the quality of salted anchovy. PhD Thesis, Faculty of Agriculture, Cairo University)

 

Holma K.A. and Maalekuu B.K., 2013, Effect of traditional fish processing methods on the proximate composition of red fish stored under ambient room conditions, American Journal of Food and Nutrition, 3(3): 73-82

 

Khan M.A.A. and Khan Y.S.A., 2001, Insects Infestation and Preventive Measures in Dry Fish Storage of Chittagong, Bangladesh, Journal of Biological Sciences, 1(10): 963-965

http://dx.doi.org/10.3923/jbs.2001.963.965

 

Kumolu-Johnson C.A., Aladetohun N.F., and Ndimele P.E., 2010, The effects of smoking on the nutritional qualities and shelf-life of Clarias gariepinus (Burchell, 1822), African Journal of Biotechnology, 9(1): 73-76

 

Makawa Z., Kapute F., and Valeta J., 2014, Effect of delayed processing on nutrient composition, pH and organoleptic quality of pond raised tilapia (Oreochromis shiranus) stored at ambient temperature, African Journal of Food, Agriculture, Nutrition and Development, 14(3): 8872-8884

 

Mohammed M.O., 2007, A guide for tradition preservation methods of fish curing, Journal of the Sudanese Standards and Metrology Organization, 1: 1-33

 

Mujumdar A.S., 2007, Handbook of Industrial drying, Taylor and Francis group, UK

 

Ojutiku R.O., Kolo R.J., and Mohammed M.L., 2009, Comparative study of sun drying and solar tent drying of Hyperopisus bebeoccidentalis, Pakistan Journal of Nutrition, 8(7): 955-957

http://dx.doi.org/10.3923/pjn.2009.955.957

 

Oparaku N.F., and Mgbenka B.O., 2012, Effects of electric oven and solar dryer on a proximate and water activity of Clarias gariepinus fish, European Journal of Scientific Research, 81: 139-144

 

Pace R.D., Plahar W.A., and Lu J.Y., 1989, Status of Traditional Food Preservation Methods for Selected Ghanaian Foods, Food Reviews International, 3(1): 1-12

http://dx.doi.org/10.1080/87559128909540842

 

Rorvik L.M., 2000, Listeria monocytogenes in the smoked salmon industry, International Journal of food Microbiology, 62:183-190

http://dx.doi.org/10.1016/S0168-1605(00)00334-2

 

Sallam K.I., 2007, Chemical, sensory and shelf life evaluation of sliced salmon treated with salts of organic acids, Food Chemistry, 101(2): 592–600

http://dx.doi.org/10.1016/j.foodchem.2006.02.019

 

Smith G. and Hole M., 1991, Browning of salted sun-dried fish, Journal of the Science of Food and Agriculture, 55: 291–301

http://dx.doi.org/10.1002/jsfa.2740550214

 

Sveinsdottir K., 1998, The Process of fish smoking and Quality evaluation, MSc. Dissertation, University of Denmark.

International Journal of Aquaculture
• Volume 6
View Options
. PDF(343KB)
. FPDF
. HTML
. Online fPDF
Associated material
. Readers' comments
Other articles by authors
. Nevarson C.J. Msusa
. Fanuel Kapute
. Jeremy S. Likongwe
. Daniel C. Sikawa
. Austin H. Mtethiwa
Related articles
. Rhamphochromis species
. Fillets
. Smoking
. Salting
. Proximate Composition
Tools
. Email to a friend
. Post a comment

ass fuck sexo anal Gruppen Pornos Blondine Pornos inzest porn hd