Sensory analysis, consumer preference and meat quality of wild versus farmed tilapia on the Malawian market

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Stellenbosch : Stellenbosch University
ENGLISH ABSTRACT: Fish is a healthy food and contribute significantly to global food security, nutrition, and trade. Tilapia from both wild and farmed sources is a popular fish and contributes to global fish supply. There is lack of published information on tilapia supply, quality, consumption patterns and consumer preference for tilapia in Southern Africa. The aim of this study was to review tilapia consumption trends, assess consumer preference, analyse sensory profile, identify tilapia species, and determine the proximate composition, fatty acid profile and heavy metal concentration of wild versus farmed tilapia on the Malawian market. The objectives of this study were 1)to review literature on tilapia consumption in Southern Africa focusing on supply, quality, and consumer preference for wild versus farmed tilapia for a 20-year period (2000 to 2019); 2)to assess consumer preference for wild versus farmed tilapia found on the Malawian market; 3) to identify wild and farmed tilapia species on the Malawian market using deoxyribonucleic acid (DNA) analysis; 4) to assess the sensory profile of tilapia by descriptive sensory analysis; 5) to analyse the chemical composition, fatty acid profile and heavy metal concentrations in wild versus farmed tilapia. The tilapia were from five sources namely: 1) wild tilapia from Malawi; 2) farmed tilapia from Malawi; and farmed tilapia imported from 3) China; 4)Zambia and; 5) Zimbabwe. The review covered 10 countries, namely, Angola, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa, Zambia, and Zimbabwe. The 10 countries were selected because of the significant contribution of tilapia towards economics and food security in the respective countries. FAO time series data on tilapia production and annual per capita fish supply were used for the review and covered a 20-year period from 2000 to 2019. In the consumer preference study, tilapia consumers (n=200) in Lilongwe Malawi were interviewed in a quantitative survey. Four qualitative focus group discussions (FGDs), with eight participants per group, were conducted to gain a deeper understanding of consumer preference for wild versus farmed tilapia. In the tilapia species identification study, deoxyribonucleic acid (DNA) analysis was used to identify the tilapia species while descriptive sensory analysis (by a trained panel of eight members) was used to assess the descriptive sensory quality of the tilapia. Proximate composition (moisture, crude protein, total crude fat and ash) of the tilapia was determined following standard official methods, fatty acids were analysed by gas chromatography and flame-ionization detector (GC-FID) method while inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the concentrations of heavy metals in the tilapia samples. The review of tilapia consumption data showed that wild tilapia declined while farmed tilapia and tilapia imports, particularly from China, contributed to fish supply in Southern Africa. Tilapia capture data for Malawi showed a declining trend from the year 2007 to 2019, although a few peaks were observed in some years (2005 to 2010). Among the 10 countries, Zambia was the leading producer of farmed tilapia. In 2000, Zambia produced 4020 tonnes of farmed tilapia, and this grew to 38390 tonnes in 2019. In 2019, Zambia produced over half of the total farmed tilapia in Southern Africa. The increases in farmed tilapia imports demonstrated the potential acceptability of farmed tilapia. The consumer preference study showed that consumers (98%, n=197) were aware of the various types and sources of tilapia sold on the Malawian market (wild versus farmed and locally produced versus imported tilapia). Sixty five percent (n = 130) of the consumers preferred wild tilapia from Malawi due to its quality (appearance, aroma, taste, and texture) even though they perceived the price of the wild tilapia to be higher than that of farmed tilapia. Forty two percent (n = 84) of the consumers often purchased wild tilapia while 34% (n = 67) purchased farmed tilapia. Correspondence analysis (CA) revealed that consumers from high tilapia consumption frequency (1-2 times tilapia consumption per week) were more likely to purchase frozen farmed tilapia than consumers from medium (1-2 times tilapia consumption per month) and low tilapia consumption frequency (5-6 times tilapia consumption per year). DNA analysis revealed that all the wild and farmed tilapia analysed showed over 98% similarity with Oreochromis niloticus in a search in GenBank and they were identified as Oreochromis niloticus. The sensory analysis experiment showed that there were statistical differences in only three sensory attributes of the fish evaluated in this study (musty mouldy aroma, earthy flavour, and musty mouldy flavour). The chemical analyses showed that farmed tilapia from Malawi had the highest total fatty acid concentration (115.62 mg/g) and all specific fatty acids except C22:0 and C20:5n3 only while wild tilapia from Malawi had the lowest total fatty acid concentration (23.06 mg/g). All the tilapia analysed in this study contained relatively high amounts of essential minerals particularly potassium (K), phosphorus (P), sodium (Na), magnesium (Mg), and calcium (Ca). Potassium was higher than Na in all the tilapia analysed. All non-essential heavy metals in all the tilapia were below the maximum recommended limits according to Food and Agriculture Organisation (FAO) and World Health Organisation (WHO) standards. The study provides valuable insights for policy analysis and development of strategies to upscale sustainable aquaculture and fisheries and facilitate fish trade by demonstrating demand and supply gaps, elucidating consumer preference, and purchasing behaviour, and providing updated information on the chemical composition of tilapia on the Malawian market.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
Thesis (PhDAgric)--Stellenbosch University, 2023