Decontamination of polycyclic aromatic hydrocarbons, organochlorine pesticides and microbial load in processed fish in Ghana using gamma irradiation: implications and prospects

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) and Organochlorine pesticides (OCPs) are among the most hazardous class of organic chemicals in the environment. Some PAHs and OCPs have been banned or restricted in several countries. The major sources of PAHs include incomplete burning of coal, oil, wood, gas and charcoal grilled meat and fish. Major sources of OCPs include food industries, agriculture and sewage wastes. Their discharge into water bodies and food result in extremely high concentrations which ultimately cause environmental and public health concerns. Due to their high persistence, toxicity and potential to bio-accumulate, their removal from salted, smoked and sundried fish through the use of gamma irradiation is imperative. In this study the levels of seven polycyclic aromatic hydrocarbons (PAHs) and eight pesticides including three organochlorine pesticides (OCPs) residues were investigated in six (6) selected frequently consumed salted, smoked and sun dried fish collected from nine markets in three coastal Regions of Southern Ghana. Gas chromatographic-mass spectrophotometer with limit of detection of 1.0 parts per billion was employed for the analysis of PAHs. Quantification of OCPs and synthetic pyrethroids was carried out before and after irradiation by Electron capture detector (ECD) and of organophosphorus by Pulse flame photoelectric detector (PFPD) with the limit of detection of 0.01parts per million (ppm) or 10 parts per billion. The safety and quality of the fish were analysed using standard methods of Association of Analytical Chemists (AOAC), 2000. Observed mean of PAHs levels in the non-irradiated smoked fish samples ranged from 11.75 – 39.37ug/kg, (p ≥ 0.05) with B(b)F recording the highest of 39.37ug/kg, (p ≥ 0.05). Non-irradiated samples of sun dried fish recorded PAHs values ranged from 5.76 – 47.68ug/kg, (p ≥ 0.05). Gamma irradiation degradation of PAHs in sun dried fish ranged between 0.32 – 29.73ug/kg (p ≥ 0.05) at 7.5kGy with B(b)F degraded from 39.37 to 29.73ug/kg, (p = 0.406) and in smoked fish, 7.54 – 22.30ug/kg (p ≥ 0.05) at 7.5kGy. B(b)F in smoked fish degraded from 33.55 – 22.30ug/kg (p ≥ 0.05) at 7.5kGy. Pesticides and OCPs in the non-irradiated samples ranged from 0.1 - 93mg/kg and after gamma irradiation, the values reduced ranging from nondetction to 29.73mg/kg (p = 0.001) in sun dried fish samples. OCPs were reduced by gamma irradiation at 7.5kGy from 0.86 – 0.007mg/kg (p = 0.001) in Cyfluthrin and from 0.768mg/kg to non-detection (p = 0.001) at 7.5kGy in Permathrin. Proximate and microbial values of smoked fish ranged as follow: Percentage weight loss (1.07±0.41), percentage moisture loss (0.02±0.02 – 9.86±0.88), percentage FFA (6.31 ± 0.00 – 8.44 ± 0.78), percentage protein loss (0.03±0.00 - 0.10±0.01), pH (6.08±0.33 – 7.38 ± 0.15), TVC logcfu/g (2.78±1.45 – 4.79 ±1.45), and MYC logcfu/g (1.90 ±0.49 – 4.14 ± 0.49). Sun dried fish recorded the following values: percentage moisture loss (0.07±0.12 – 0.31±0.12), percentage weight loss (0.05±0.02 – 0.08±0.02), percentage protein loss (0.06 ± 0.08– 0.21 ± 0.08), percentage ash (10.13 ± 2.27 – 14.66 ± 2.27), percentage FFA (2.80 ±0.71 – 4.22 ± 0.71), percentage TTA (5.33 ± 0.62 – 6.57 ± 0.62), percentage pH (6.78 ± 0.1 – 6.98 ± 0.1), TVC logcfu/g (4.80 ± 0.16 – 5.12 ± 0.16) and MYC logcfu/g (4.39 ±0.45 – 5.28 ± 0.45). On basis of the above findings, this thesis attempts to provide an assessment on the potential of using gamma irradiation as a means to improve health and safety standards of salted, smoked and sun-dried marine and freshwater fishes. Recommendations proffered included increasing the irradiation dose to maximum of 10kGy for food in further study for the reduction of PAHs and pesticides. Protocols to regulate and enhance quality and safety of smoked and sun dried fish will add to acceptance for the export of smoked and sun dried fish from Ghana. Pesticides residue levels must be set by the Ghana‘s Food and Drugs Authority to monitor the activities of fish processors in consonance with international standards. These are particularly worthy for the attention of policy makers, fish processors, Fisheries Commission of Ghana, NGOs and the general promotion of food safety in the country.