Department of Marine and Fisheries Sciences
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Item Assessing The Efficiency Of Two Improved Lesser Known Kilns And Their Effect On The Quality And Shelf Life Of Smoked Fish In Ghana(University of Ghana, 2019-07) Asamoah, E.K.Fish smoking is a traditional fish preservation method which is affordable, and hence employed in most developing countries with logistical challenges in preserving fresh fish for marketing. Smoked fish is a major source of protein in the diets of Ghanaians. Often traditional kilns, that rely on firewood as a source of fuel, are used. These kilns have been shown to be less fuel efficient and the smoked products have high levels of polycyclic aromatic hydrocarbons (PAHs), which are of public health concern. Additionally, poor storage of the products leads to quality losses. This study, which contributes to the search for a more efficient and safe smoking oven, therefore sought to test and compare the efficiency of two improved, but lesser known kilns, the Cabin and Abuesi gas fish smoker (AGFS) to the traditional Chorkor smoker by investigating the physicochemical, microbial and sensory qualities of the smoked products. Finally, the effect of irradiation and different storage conditions on the shelf life of the smoked products was studied. The research was undertaken in Abuesi, in the Western Region, using two marine fish species, the chub mackerel and barracuda. The results showed that the AGFS had 12% lower yield but 86% and 60% higher processing rate than the cabin and Chorkor kilns respectively. Again, the fuel consumption was 68% and 54% better than the Cabin and Chorkor respectively, while the Cabin also saved 29% more fuel than the Chorkor. In terms of the fuel costs, the Cabin was 38% and 54% lower than the Chorkor and AGFS respectively (owing to the lower cost of firewood, compared to LPG). The cost of construction was however extremely high in the AGFS than the Cabin and Chorkor kilns, however, its industrial size (500 kg capacity), faster smoking time and lower fuel consumption make it good alternative to consider. Smoking improved the physical, chemical, microbiological and sensory quality of mackerel and barracuda. These qualities, except for colour and sensory analysis, could not be statistically differentiated between the products from the AGFS and Cabin kiln. The Cabin-smoked products had the more traditional qualities of smoked fish (appearance, odour and flavour), while the gas-smoked products had a pronounced fried appearance and taste. The AGFS produced smoked products with mean benzo(a)pyrene and PAH4 concentrations below the EU MLs (2 and 12 μg/kg respectively). Depending on the type of firewood used, the Cabin also produced benzo(a)pyrene below the MLs when C. mildbraedii (Esa) was used, while the Chorkor had levels 3 to 8 times higher than the MLS. The PAH4 levels in the Cabin and Chorkor products were all above the MLs (4 and 8 times higher respectively). Based on the frequency and quantities of smoked mackerel and barracuda consumed by an average Ghanaian adult (with a life expectancy of 63 years), the potential carcinogenic risks were of least concern in the gas smoked and all barracuda samples (about 1 in 100,000 adults), moderate in the Cabin smoked mackerel (3 and 6 in 100,000 adults) and high in the Chorkor smoked mackerel (7 and 17 in 100,000 adults). Heavy metal (Hg, Pb and Cd) contamination was negligible in fresh and smoked mackerel and barracuda. The effect of irradiation and storage temperature on the quality and shelf life of smoked mackerel showed that irradiation did not affect the nutritional quality (protein, fat, moisture and ash contents) after 65 days of refrigerated storage. The fatty and amino acid compositions were also unaffected by irradiation. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) respectively constituting about 8% and 18% of the total fatty acids. The essential amino acids also contributed about 59% of the total amino acid concentrations. The non-irradiated and irradiated smoked mackerel, stored at refrigerated temperature, were of good microbial and chemical quality by Day 65 of storage, even though lipid oxidation and hydrolysis were affected. Keeping the non-irradiated and irradiated smoked fish at room temperature were rejected by Day 5 of storage due to insect infestation and visible mouldiness (even though most microbial and chemical qualities were good). The results, therefore, indicates that The AGFS performed better, overall, followed by the Cabin and then the Chorkor. The kilns produced fish with good nutritional qualities. Irradiation did not negatively impact on the quality of the smoked products during the 65 days of storage, but refrigerated storage is key to maintaining quality of irradiated fishItem Assessing the Efficiency of Two Improved Lesser Known Kilns and Their Effect on the Quality and Shelf Life of Smoked Fish in Ghana(University of Ghana, 2019-07) Asamoah, E.K.Fish smoking is a traditional fish preservation method which is affordable, and hence employed in most developing countries with logistical challenges in preserving fresh fish for marketing. Smoked fish is a major source of protein in the diets of Ghanaians. Often traditional kilns, that rely on firewood as a source of fuel, are used. These kilns have been shown to be less fuel efficient and the smoked products have high levels of polycyclic aromatic hydrocarbons (PAHs), which are of public health concern. Additionally, poor storage of the products leads to quality losses. This study, which contributes to the search for a more efficient and safe smoking oven, therefore sought to test and compare the efficiency of two improved, but lesser known kilns, the Cabin and Abuesi gas fish smoker (AGFS) to the traditional Chorkor smoker by investigating the physicochemical, microbial and sensory qualities of the smoked products. Finally, the effect of irradiation and different storage conditions on the shelf life of the smoked products was studied. The research was undertaken in Abuesi, in the Western Region, using two marine fish species, the chub mackerel and barracuda. The results showed that the AGFS had 12% lower yield but 86% and 60% higher processing rate than the cabin and Chorkor kilns respectively. Again, the fuel consumption was 68% and 54% better than the Cabin and Chorkor respectively, while the Cabin also saved 29% more fuel than the Chorkor. In terms of the fuel costs, the Cabin was 38% and 54% lower than the Chorkor and AGFS respectively (owing to the lower cost of firewood, compared to LPG). The cost of construction was however extremely high in the AGFS than the Cabin and Chorkor kilns, however, its industrial size (500 kg capacity), faster smoking time and lower fuel consumption make it good alternative to consider. Smoking improved the physical, chemical, microbiological and sensory quality of mackerel and barracuda. These qualities, except for colour and sensory analysis, could not be statistically differentiated between the products from the AGFS and Cabin kiln. The Cabin-smoked products had the more traditional qualities of smoked fish (appearance, odour and flavour), while the gas-smoked products had a pronounced fried appearance and taste. The AGFS produced smoked products with mean benzo(a)pyrene and PAH4 concentrations below the EU MLs (2 and 12 μg/kg respectively). Depending on the type of firewood used, the Cabin also produced benzo(a)pyrene below the MLs when C. mildbraedii (Esa) was used, while the Chorkor had levels 3 to 8 times higher than the MLS. The PAH4 levels in the Cabin and Chorkor products were all above the MLs (4 and 8 times higher respectively). Based on the frequency and quantities of smoked mackerel and barracuda consumed by an average Ghanaian adult (with a life expectancy of 63 years), the potential carcinogenic risks were of least concern in the gas smoked and all barracuda samples (about 1 in 100,000 adults), moderate in the Cabin smoked mackerel (3 and 6 in 100,000 adults) and high in the Chorkor smoked mackerel (7 and 17 in 100,000 adults). Heavy metal (Hg, Pb and Cd) contamination was negligible in fresh and smoked mackerel and barracuda. The effect of irradiation and storage temperature on the quality and shelf life of smoked mackerel showed that irradiation did not affect the nutritional quality (protein, fat, moisture and ash contents) after 65 days of refrigerated storage. The fatty and amino acid compositions were also unaffected by irradiation. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) respectively constituting about 8% and 18% of the total fatty acids. The essential amino acids also contributed about 59% of the total amino acid concentrations. The non-irradiated and irradiated smoked mackerel, stored at refrigerated temperature, were of good microbial and chemical quality by Day 65 of storage, even though lipid oxidation and hydrolysis were affected. Keeping the non-irradiated and irradiated smoked fish at room temperature were rejected by Day 5 of storage due to insect infestation and visible mouldiness (even though most microbial and chemical qualities were good). The results, therefore, indicates that The AGFS performed better, overall, followed by the Cabin and then the Chorkor. The kilns produced fish with good nutritional qualities. Irradiation did not negatively impact on the quality of the smoked products during the 65 days of storage, but refrigerated storage is key to maintaining quality of irradiated fish.Item Investigations into Hatchery and Nursery Operations for the Culture of the Freshwater Prawn (Macrobrachium Vollenhovenii, Herklots 1857) in Ghana(University of Ghana, 2018-07) Dzidzornu, K.E.A.The study was conducted to demonstrate hatching and larval development of the African River Prawn Macrobrachium. vollenhovenii Herklots, 1857) and to establish the spatial and temporal distribution of the prawns and related crustaceans in the Lower Volta River from Torgorme (Akuse) to Ada with focus on the Volta Estuary of Ghana. The ecological survey was undertaken from August 2013 to July 2014 followed with aspects of reproductive biology of the M. vollenhovenii from August 2014 to July 2015 and then the hatching and larval development of the from January to December 2016. Fisheries dependent data was collected together with experimental prawn fishing. The species encountered included Atya gabonensis (Giebel, 1875), Macrobrachium macrobrachion, (Herklots, 1851), Macrobrachium vollenhovenii and Penaeus spp. Comparatively more Penaeus spp. were sampled in the dry months (November to January) in more saline zones while Macrobrachium spp. were more in the rainy months (May to July) in the more freshwater zones. The dominant species in the estuary was the M. vollenhovenii (72.52%) with male to female ratio of 1:1.3 and non-berried to berried females ratio as 1:1.7. The berried females were obtained throughout the year with increased numbers and larger ones in the rainy season. The size and weight of gonad correlated positively with size of berried females and appeared to be a function of the number rather than the size of eggs. Out of four treatment media (Artificial Sea salt, Freshwater, Seawater and Rock salt) used for the larval development, the Freshwater medium could not support the life of the larvae after 48 hours. The 8th Larval stage (ZVIII) was observed from the 23rd day of culture in both Seawater and Artificial Sea Salt media. Survival rate correlated negatively with stocking densities of 50, 100, 150 and 200 larvae/liter, an indication that thinning is necessary as the larvae grow from one stage to another. Survival rates in the 50 larvae/liter were 36.8%, 30.8% and 25% in the Seawater, Artificial Sea salt and Rock salt treatments respectively. From the results, M. Vollenhovenii larvae could be hatched and developed for culture in the grow-out process to boost prawn culture in Ghana.Item Geochemistry of Estuarine Sediments of Ghana: Provenance, Tracemetal Accumulation Trends and Ecotoxicological Risks(University Of Ghana, 2014-07) Mahu, E.The sedimentary record, as revealed in sediment cores, can be used to reconstruct the past history of contaminant input into the aquatic environment. This is because contaminant inputs equilibrate rapidly with sediment supply, and the sediment column represents a continuous sequence of sediments that are associated with contaminant accumulation. With radiometric techniques, it is possible to date recent sediments over a period corresponding to about five half-lives (approximately 100-200 years using 210Pb). To understand the geochemistry of estuarine sediments in relation to their provenance, trace metal accumulation trends and potential ecotoxicological risks, this study investigated sediment cores and surficial sediments from the Ankobra, Pra, Amisa, Densu, Sakumo II and Volta estuaries of Ghana. Geochemical and petrographical techniques were used to reveal the source of sediment supply into the estuarine environments. In addition, Gamma Spectroscopy and Inductively Coupled Plasma Mass Spectrometric (ICP-MS) techniques were used for deriving geochronologies, sedimentation rates, spatial and temporal accumulation of Mo, Cd, Pb, V, Cr, Cu, Zn, As and Hg in the study sites. The pollution status of the estuarine sediments was investigated using Aluminum-normalized enrichment factors (EFs). Cluster and correlation analysis differentiated natural from anthropogenic sources of trace metal in the estuaries. The excess fluxes of trace metals, estimated using sedimentation rates helped in quantifying the extent of anthropogenic contamination of metals in each estuary. AQUARISK software was used to assess any potential ecotoxicological risks associated with trace metal enrichments. Results showed that sediments from the Ankobra, Pra, Densu and Volta estuaries comprised quartzose sedimentary provenance while those of Amisa and Sakumo II estuaries comprised mafic igneous provenance. The sedimentation rates estimated from the constant rate of supply model were 0.24±0.10 gcm-2y-1, 0.47±0.20 gcm-2y-1, 0.43±0.02 gcm-2y-1, 0.31±0.13 gcm-2y-1, 0.20±0.01gcm-2y-1 and 0.54±03 gcm-2y-1 for the Ankobra, Pra, Amisa, Densu, Sakumo II and Volta estuaries respectively. The sediment core from the Ankobra estuary was significantly enriched with Hg (5.0