Detection of illegal addition of formaldehyde to fresh fish
1996
Tunhum, Dusadee (Sing Buri Agricultural College, Sing Buri (Thailand).) | Kanont, Sombat | Chaiyawat, Mayuree | Raksakulthai, Nongnuch
The formaldehyde content of fresh fish in Bangkok markets was very low in chub mackerel, rake-gilled markerel (RGM) and Indo-Pacific king mackerel (below 1.0 mg/kg) but higher in silver pomfret (1.5 mg/kg). It was concluded that the formaldehyde content depended on the species of fish (P less than 0.01). Formaldehyde increased from 0.50 to 1.4 mg/kg during frozen storage of RGM at -20 degree C whilst in lizard fish (LF) it increased from 16.8 to 42.5 mg/kg after six months. In RGM and LF, dipped in different concentrations of formaldehyde solution for 10 minutes, the analysed concentrations correlated well with the concentrations used (r equal to 0.9955 for RGM and 0.9904 for LF). The predicted equations were: Formaldehyde in RGM (mg/kg) equal to 0.8185 + 0.0067x.....(1) Formaldehyde in LF (mg/kg) equal to 18.5170 + 0.0097x......(2) where x equal to formaldehyde concentration in diluted formaldehyde solution used (mL/L). Sensory evaluation indicated that formaldehyde could be detected in RGM and LF dipped in solutions containing more than 500 and 2000 mL/L formaldehyde, respectively. The judges could perceive a formaldehyde smell from cooked fish only immediately after cooking if more than 1000 mL/L of formaldehyde solution was applied. In addition, the texture of those cooked samples was harder and tougher than the controls.
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