Studies were conducted to evaluate the effects of
formalin (0.5%, 1.0%, 1.5%, 2.0% and 2.5%)on short-term preservation of Puntius
ticto from June, 2005 to July, 2006. To do that, both
organoleptic,
histological and chemical techniques were used. The organoleptic
evaluation was carried out with the help of sense organs, particularly through smelling, tasting, touching and visualizing the external body color. The fresh condition of Puntious ticto was identified by the presence of transparent and shiny-silver body with mucous coating, bright red colored gills, eyes with transparent cornea and convex eyeballs, bright pinkish colored muscle, firmly attached scales transparent mucus and compressed belly. The body color turned grey in 0.5%, 1%, 1.5% formalin and dull in 2% and 2.5% formalin after 8 hours. Dull color was appeared in all grades after 24 hours. Gill color altered red to grey after 8 hours in 2% and 2.5% grades; then to deep grey in all grades after 24 hours. The cornea became dull within 8 hours and remain till 16 hours in all grades. After 24 hours it was opaque. Eyeball became settled after treating with formalin from the very beginning after 4 hours. The muscle texture was compact after 8 hours and then to become elastic after 16 hours and finally to hard after 24 hours in all grades of formalin. The scales were compressed and shiny in 0.5% formalin treated fish but, altered color in all other grades after 8 hours. They stated to shed after 24 hours. After 24 hours, the belly was found swelled and fish found sunken in pot. Histologically, cell diameter of dark muscle was
decreased from 1.4 mm to 0.20 mm and extra cellular space was increased from 0.18 mm to 0.75 mm in case of 0.5%, 1%, 1.5%, 2% and 2.5% formalin preserved fish. Formalin caused to increase cell numbers consequently along the long time of preservation. Moreover, dark muscle cell was scattered in case of 2% and 2.5% formalin treated fish after 24 hours. The percentage of moisture contents of fresh fish decreased from 76.88% to 68.14%, the protein contents sharply decreased from 18.83% to 16.06% and the ash contents decreased from 7.07% to 2.85% within 24 hours for the use 0.5% to 2.5% formalin as a preservative. The fat content gradually decreased from 2.06% to 0.86% within 24 hours. In conclusion, different grades of formalin negatively affected the organoleptic indices, altered cell dimension and structure and significantly influenced
biochemical composition of Puntius ticto.
Key words: formalin effect, indigenous fish, organoleptic, histological, biochemical composition
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