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 FNS  Vol.4 No.11 , November 2013
Acidity/Rancidity Levels, Chemical Studies, Bacterial Count/Flora of Fermented and Unfermented Silver Catfish (Chrysichthys nigrodigitatus)
Abstract: The keeping quality and shelf life of fermented and unfermented Chrysichthys nigrodigitatus were monitored in this study. Four kilograms of fresh Chrysichthys nigrodigitatus was minced into fine particles (with an initial pH of 7.2 before distribution into 8 samples). Samples 1-4 are unfermented cooked while Samples 5-8 were fermented, not cooked. All the 8 prepared samples barely lasted for two weeks, while samples 1, 3 and 7 lasted for six weeks. Total Volatile Base (TVB) ranged higher (24.12 - 29.43) mg/100gm in Samples 1-4 than (14.23 - 18.09) mg/100gm recorded in Samples 5-8. In Samples 1-4, FFA values were not significantly (P > 0.05) different; also followed a narrow range of (6.14 - 6.45)% while higher range of (6.42 - 12.27)% recorded in samples (5-8). Peroxide values (PV) increased in all the 8 samples in the second, fourth and sixth week, however higher values were recorded in Samples 5-8. Acidity generally increased with length (weeks) of fermentation with a gradual drop in pH from 7.2 (in the fresh fish) to pH 4.5 (sample 7), the worst sample at six weeks. Sample 4 with bacteria load of 5.05 × 105 at second week and sample 7 (8.2 × 105) at sixth week became unfit for consumption having exceeded the 5.0 × 105 ICMSF standard for safe fish product. Five bacteria species (Lactobacillus sp, Proteus spp, Staphylococcus aureus, Staphylococcus epidermis, Bacillus sp) with the exception of Proteus spwere not represented in sample 1 (due to salt content). Strong positive correlation (r = 0.97, P < 0.01) exists between PV and FFA. Acidityof the fermented products increased over the weeks with strong negative correlation (r = -0.121, P < 0.01) exists between pH and FFA. Acidity (i.e drop in PH) with increasing rancidity since (r = -0.313, P < 0.05) exists between PV and pH.
Cite this paper: O. Oyelese, O. Sao, M. Adeuya and J. Oyedokun, "Acidity/Rancidity Levels, Chemical Studies, Bacterial Count/Flora of Fermented and Unfermented Silver Catfish (Chrysichthys nigrodigitatus)," Food and Nutrition Sciences, Vol. 4 No. 11, 2013, pp. 1155-1166. doi: 10.4236/fns.2013.411149.
References

[1]   N. Zakhia and J. L. Cuq, “Apercu sur la Qualite du Tilapia Secheetcommercialise au Mali,” Proceedings of the FAO Expert Consultation on Fish Technology in Africa, Accra, 22-25 October 1991.

[2]   H. H. Huss and G. Valdimarson, “Micro-Biology of Salted Fish,” FAO Food Tech News, Vol. 10, No. 1, 1990, p. 190.

[3]   B. Klinic, “Fish Sauce Technology,” EUJ Fish Aquat. Sci, Vol. 20, No. 1-2, 2003, pp. 263-273.

[4]   FAO, “Fermented Fish Products,” Prepared by I. M. Mackie, R. Hardy and G. Hobbs, FAO Fish Rep., Vol. 100, 1971, p. 54.

[5]   K. M. Essuman, “Fermented Fish in Africa. A Study on Processing,” Marketing and Consumption FAO Fisheries Technical Paper No 329, FAO, Rome, 1992, 80 p.

[6]   K. K. Eyeson, “Composition of Foods Commonly Used in Ghana,” Food Research Institute (CSIR), Accra, 1975.

[7]   A. A. Eyo, “Fish Processing Technology in the Tropic National Institute for Freshwater Fisheries Research (NIFFR),” New Bussa, 2001, pp. 10-170.

[8]   J. C. D. Watts, “Some Observations on the Preservation of Fish in Sierra Leone,” Bulletin de MPANTXXVII Sci. of No. 1, 1965.

[9]   K. Watanabe, “Fish Handling and Processing in Tropical Africa,” Proceedings of the FAO Expert Consultation on Fish Technology in Africa, Casablanca, 7-11 June 1982, FAO Fish. Rep, Vol. 268, 1982, pp. 1-5.

[10]   N. I. Azeez, “The Problem of Choice and Safer Methods of Reducing Post Harvest Losses in Lake Chad Processed Fish,” Proceedings of the FAO Expert Consultation on Fish Technology in Africa, Lusaka, 21-25 January 1985, FAO Fish, Rep., Vol. 329, 1986, pp. 340-348.

[11]   G. M. Reay and J. M. Shewan, “The Spoilage of Fish and Its Preservation by Chilling,” Advances in Food Research, Vol. 2, 1949, pp. 343-389. http://dx.doi.org/10.1016/S0065-2628(08)60047-6

[12]   Y. Tomiyasu and W. B. Zenitani, “Spoilage of Fish and Its Preservation by Chemical Agents,” Advances in Food Research, Vol. 7, 1957, pp. 41-82.
http://dx.doi.org/10.1016/S0065-2628(08)60246-3

[13]   D. Pearson, “Chemical Analysis of Foods,” 7th Edition, Churchill Livingstone, Edinburg, 1962.

[14]   Oyelese and Odubayo, “Shelf Life of Fish Meal Paste and Cake of Tilapia niloticus and Supplementation of Con vertional Fishmeal with Tilapia Fishmeal in the Diet of Clariasgariepinus Fingerlings,” Journal of Food Process ing and Preservation, Vol. 34, Suppl. 1, 2010, pp. 149 163. http://dx.doi.org/10.1111/j.1745-4549.2008.00330.x

[15]   A.O.A.C., “Official Methods of Analysis of AOAC International,” 17th Edition, 1st Revision, Association of Analytical Communities, Gaithersburg, 2002.

[16]   ICMSF, “International Commission on Microbiological Specifications for Foods. Micro-Organisms in Foods 7. Microbiological Testing in Food Safety Management,” Kluwer Academic Plenum Publishers, New York, 2002, p. 199.

[17]   D. F. Hiltz, “Deteriorative Changes during Frozen Storage in Fillets and Minced Flesh of Silver Lake (Mertuucciusbilineans) Processed from Round (Whole) Fish Held in Ice and Refrigerator Sea Water,” Journal of the Fisheries Research Board of Canada, Vol. 33, No. 11, 1976, pp. 2560-2567. http://dx.doi.org/10.1139/f76-300

[18]   W. F. A Horner, “Preservation of Fish by Curing (Drying, Salting and Smoking),” In: G. M Hall, Ed., Fish Processing Technology, 2nd Edition, Chapman and Hall, New York, 1997, pp. 21-39.
http://dx.doi.org/10.1007/978-1-4613-1113-3_2

 
 
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