A. M. Omemu

Effect of smoking methods on microbial safety, polycyclic aromatic hydrocarbon, and heavy metal concentrations of traditional smoked fish from Lagos State, Nigeria

ABSTRACT A study was carried out to investigate the effect of smoking methods on microbial safety, polycyclic aromatic hydrocarbon, and heavy metal concentrations of traditional smoked fish from Lagos State, Nigeria. One hundred samples of fresh fish were obtained from 20 different fishing communities/processing centers. The fresh fish samples were divided into two batches: The first batch was smoked with drum kiln and the second batch was immediately taken to the Fish Hatchery Unit, Federal University of Agriculture, Abeokuta for smoking with convective kiln. Laboratory analyses were carried out on the two batches for: microbiological (Coliform, Fuugi, Listeria monocytogenes, Salmonella paratyphi and Staphylococcus aureus), polycyclic aromatic hydrocarbon and heavy metals (mercury, lead, cadmium and chromium). The results of the microbiological, polycyclic aromatic hydrocarbon and heavy metal analyses revealed that there were significant variations (p < 0.05) between them. LC count of fresh silver catfish, spotted tilapia, bonga shad, Nigerian tongue sole, and Guinea barracuda samples were 1.9 × 102, 1.7 × 102, 2.0 × 102, 2.1 × 102 and 2.6 × 102 cfu/g and their drum kiln smoked samples were 4.0 × 10, 5.3 × 101, 6.0 × 101, 12.2 × 101 and 7.4 × 101 cfu/g, respectively, while samples from convective smoking kiln contain no strain of Listeria monocytogenes. The concentrations of the six major PAHs (fluorene, anthracene, benzo [b] fluoranthene, benzo [a] anthracene, benzo [a] pyrene and benzo [ghi] perylene) in the drum-smoked fish exceeded the EU maximum level of 5.0 μg/kg for BaP permissible in smoked fish, while samples smoked by convective smoking kiln showed levels below 3.5 μg BaP/kg. The study also showed that the levels of the four heavy metals investigated in the smoked fish samples are generally below the maximum permissible levels set by World Health Organization for Hg (0.2 ppm), Pb (0.3 ppm), Cd (0.2 ppm), and Cr (0.5 ppm) and hence pose no risk to smoked fish consumers.

Assessment of quality and safety of traditional smoked spotted tilapia fish (Tilapia mariae) from Lagos State, Nigeria

Purpose – This study aims to assess the quality and microbial safety of traditional smoked spotted tilapia fish from Lagos State and, by doing so, determine the quality and microbial safety level of traditional smoked spotted tilapia fish, their distribution, effects and possible public health implications of the quality/rancidity indices and microorganisms on the consumers. Design/methodology/approach – Fresh spotted tilapia fish (100 samples) were collected from 20 different fishing/processing centres and divided into two batches. One batch was smoked with local drum kiln at processing centres, and the second batch was smoked with convective smoking kiln as control in the laboratory. Each batch was assessed for moisture content, protein content, fat content, crude fibre content, ash content, pH, thiobarbituric acid (TBA), total volatile base- nitrogen (TVB-N), trimethylamine (TMA), peroxide value (PV) and free fatty acid (FFA) values. Microbiological analyses were also conducted. Each batch was assessed...

Quality characteristics and chemical safety of fried and smoked West Africa Ilisha (Ilisha africana) from Ibadan, Oyo State, Nigeria

Purpose – This study aims to assess and compare the quality and safety of street-vended, ready-to-eat fried and smoked West African Ilisha fish from the major markets in Ibadan, Oyo State, Nigeria. Design/methodology/approach – A total of 50 samples each were obtained from ten major markets in Ibadan, Oyo State, Nigeria. Samples were analyzed in the laboratory for proximate, rancidity indices; i.e. peroxide value (PV), thiobarbituric acid (TBA), total volatile base-nitrogen (TVB-N), trimethylamine acid (TMA) and free fatty acid (FFA), polycyclic aromatic hydrocarbon (PAH) and heavy metals. Findings – The results showed that the mean PV (meq. peroxide/kg), TBA (mg Mol/kg), TVB-N (mgN/kg), TMA (mgN/kg) and FFA (%) contents within the fried fish samples ranged from 18.86-23.11, 2.08-2.98, 14.89-17.79, 1.98-2.89 and 2.46-5.98, respectively, while in the case of smoked fish samples, the corresponding contents were found to be 9.03-15.96, 1.03-1.59, 17.29-19.36, 2.15-2.68 and 1.13-1.62, respectively. The result...

Microbiological assessment of traditional smoked silver catfish (Chrysichthys nigrodigitatus)

Smoked fish is relished food item in many dishes in Nigeria. Traditional smoked silver catfish (Chrysichthys nigrodigitatus) that floods the smoked fish market of the Lagos State of Nigeria are not microbiologically shelf-stable; hence, the need for a study on their microbiological quality and safety. ‘Fresh silver catfish’ (100 samples) and smoked silver catfish (100 samples) were collected from 20 different processing centres and the fresh samples were smoked with convectional smoke kiln as control and microbiological analyses were conducted. Each batch was assessed for: total viable count (TVC), fungal count (FC), Listeria monocytogenes (LM) count, Staphylococcus aureus (SA) count, Salmonella Paratyphi (SP) count and presence or absence of Escherichia coli (EC). The results obtained showed significant variations (p<0.05) for all the microbial counts of the smoked fish samples. The mean TVC range of 6.6 x 106 - 8.8 x 108 cfu/g was recorded for fresh silver catfish samples and 2.0 x 104 - 8.6 x 104 and 1.0 x 103 - 5.4 x 103 cfu/g for samples of smoked silver catfish. 5.0 x 103 - 6.4 x 103 cfu/g was recorded for fresh silver catfish samples and from 5.6 x 102 - 60.4 x 102 cfu/g and 1.0 x 102 - 3.5 x 102 cfu/g for samples of smoked silver catfish (SA). Mean (LM) of fresh silver catfish samples was 1.8 x 102 - 2.5 x 102 cfu/g and 1.3 x 101 - 13.2 x 101 cfu/g for samples of smoked silver catfish. Mean (FC) of smoked silver catfish from local drum kiln was 4.1 x 101 - 8.2 x 101 cfu/g. The samples of smoked silver catfish using conventional smoke kiln showed no count for L. monocytogenes, S. Paratyphi and E. coli. Key words: Silver catfish, smoking, traditional, Staphylococcal, Listeria monocytogenes.

Microbiological assessment of maize ogi cofermented with pigeon pea

Abstract Maize was cofermented with pigeon pea for ogi production and evaluated for microbiological qualities. White maize and pigeon pea were mixed at ratios of 90:10, 80:20, 70:30, 60:40, and 50:50, respectively, with 100:0 serving as the control. Mixtures were cofermented for 96 h at 27 ± 2°C, and microbiological and sensory qualities analyzed were carried out using analysis of variance. Values were significant at p ≤ .05. Results showed that there was a gradual decrease in the pH and increase in total titratable acidity (TTA), respectively, during fermentation in all the samples. At the end of fermentation, pH ranged from 3.47 to 4.27 and TTA ranged from 0.47% to 0.54%, respectively. Total heterotrophic count (THPC) ranged from 5.76 to 5.90 log cfu/g; lactic acid bacteria (LAB) from 6.15 to 5.98 log cfu/g; and yeasts from 5.51 to 5.79 log cfu/g. Microorganisms isolated were lactic acid bacteria (Lactobacillus buchneri, L. casei, L. pentosus, Pediococcus pentosaceus), yeasts (Saccharomyces cerevisiae, Candida kefyr, C. krusei, C. tropicalis), molds (Aspergillus niger, A. flavus, Penicillium oxalicum, Mucor racemosus and Rhizopus stolonifer) and other aerobic bacteria (Klebsiella oxytoca, Enterobacter amnigenus, Staphylococcus xylosus, Bacillus subtilis, B. firmus, Corynebacterium kutscheri, C. striatum, and C. afermentans). In conclusion, the total heterotrophic plate count (THPC) in fortified maize: pigeon pea products was very high. This could constitute health hazards to infants as weaning foods. However, the microbial loads could be reduced through heat treatment as ogi is usually boiled or treated with boiled water before consumption and it can therefore be concluded that the fortified maize: pigeon pea products could be used as weaning foods.

Effect of Smoking Methods on Quality and Safety of Traditional Smoked Fish from Lagos State, Nigeria

ABSTRACT This study was carried out to assess the effect of smoking methods on quality and safety of traditional smoked of fish from Lagos State, Nigeria. Five types of fresh fish (40) samples each were obtained from 20 different fish processing centers. The fresh fish samples were divided into two batches. The first batch was smoked with drum kiln and second batch was smoked with convective kiln. Laboratory analyses were carried out on the two batches for proximate, rancidity indices (PV, TBA, TVBN, TMA, and pH), heavy metals and microbiological (coliform, fungi, Listeria monocytogenes, Salmonella paratyphi, and Staphylococcus aureus). The results revealed that the mean MC of fresh fish samples ranged from 73.48%–75.94% and that of drum-smoked fish samples ranged from 11.86%–13.41% and 8.56%–9.36% for convective smoked fish samples. The mean PC of fresh fish samples ranged from 15.18%–17.96% and that of drum-smoked fish samples ranged from 54.80%–59.35% and 57.45%–66.23% for convective-smoked fish samples. The results of the proximate, quality, and microbiological analyses revealed that there was significant variations (p < 0.05) due to smoking methods. The study showed that the levels of the four heavy metals investigated in the fish samples are generally below the maximum permissible levels set by WHO for Pb (0.3 ppm); Cd (0.2 ppm), Hg (0.2 ppm) and Cr (0.5 ppm) and hence pose no risk to smoked fish consumers. The study concluded that traditional drum-smoked fish needs further cooking or heat treatment before it can be included in the menu, as non-heat treatment may pose higher microbiological risks to the consumers due to the presence of Listeria monocytogenes in some of the traditional drum-smoked fish samples which may constitute a threat to public health.

Quality attributes, polycyclic aromatic hydrocarbon, and heavy metal profile of traditional drum-smoked Guinean barracuda fish from Lagos State, Nigeria

ABSTRACT This study was carried out to assess the quality attributes, polycyclic aromatic hydrocarbon (PAH), and heavy metal profile of traditional drum-smoked Guinean barracuda fish from Lagos State, Nigeria. Fresh Guinean barracuda fish (60) samples were obtained from 20 different fish-processing centers. The fresh fish samples were smoked with traditional drum kiln. The fresh and smoked fish samples were analyzed for proximate composition, quality indices (peroxide value (PV), thiobarbituric acid (TBA), total nitrogen base-nitrogen (TVB-N), trimethylamine acid (TMA), and free fatty acid (FFA)), PAH, heavy metals, and microbiological (coliform, fungi, Listeria monocytogenes (LM), Salmonella paratyphi (SP), and Staphylococcus aureus (SA)) analyses. The results revealed that the mean moisture, protein, fat, crude fiber, ash, and carbohydrate contents of traditional drum-smoked fish samples were in the range 10.93–14.15%, 51.97–60.96%, 11.34–15.99%, 1.74–2.99%, 1.12–1.56%, and 7.70–17.99%, respectively. The values of PV, FFA, TBA, TVB-N, and TMA were in the range of 8.21–10.19 meq.peroxide/kg, 1.13–1.80%, 1.03–1.19 mgMol/kg, 17.29–19.36 mgN/kg, and 2.12–2.68 mgN/kg, respectively. The results of PAH compounds in the traditional drum-smoked fish samples showed that 10 of the 16 PAH compounds detected were above the 5.0 µg/kg B(α)P maximum permissible levels stipulated by EU Regulation 1881/2006. The concentrations of Hg, Pb, Cd, and Cr in the smoked fish samples ranged from 0.001 to 0.0027 µg/g, 0.0013 to 0.0028 µg/g, 0.0014 to 0.0028 µg/g, and 0.0621to 0.0796 µg/g, respectively. The results of microbiological analysis revealed the presence of LM and SA in the traditional drum-smoked fish samples. The study concluded that traditional drum-smoked fish may constitute higher risks (chemical and microbiological) and public health concerns to consumers.

The effect of processing parameters on the functional and pasting properties of breadfruit (Artocarpus Altilis) “elubo” flour

Breadfruit (Artocarpus altilis) elubo was produced using various processing parameters. A second order Box-Benhken Response Surface Design was adopted in designing the experiment which generated 17 runs on selected process parameters, including parboiling temperature (30, 50 and 60 °C), parboiling time (90, 120 and 150 min), and steeping time (6, 12 and 18 hrs) on the functional and pasting properties (bulk density, water absorption capacity, swelling power, solubility, dispersibility, and pasting characteristics) of the elubo. At high parboiling temperature and time there was an increase in bulk density, water absorption, and swelling power of the BE, while the increase in parboiling temperature and steeping time led to a decrease in peak and final viscosity. The generated models were adequately explained as their adjusted regression coefficients (Adjusted R) were between 0.56 and 0.99, this revealed that R gave a good (50<R >75%) explanation of the model. BE can be produced at an optimum condition of 60 °C, 133 min, and 10 hrs for parboiling temperature, time and steeping time, respectively, based on the desirability concept of 0.80.