FOOD RESEARCH INTERNATIONAL, vol.33, no.10, pp.839-845, 2000 (SCI-Expanded)
This study describes the modifications necessary to apply the colorimetric method for histamine detection in fish meal. Although the original colorimetric method works well with fish flesh, difficulties were observed during filtration of the homogenised sample and column separation when it was applied to fish meal. In this study, the reason for the problems encountered was studied by processing fish meal using different parts of fish. It was found that the problem was caused by the presence of bone in the sample, which suggested that calcium in bone reacted with potassium hydroxide (KOH) used to adjust pH during the experiment. This was confirmed by a chemical test reacting calcium carbonate with KOH solutions at different concentrations. The reaction was reversible in acidic conditions with trichloracetic acid (TCA) or hydrochloric acid (HCl). Several tests were applied before the filtration and neutralization stage of the method to solve the problems occurred. Centrifugation of the homogenised sample ∼ 20 min at 23 000 g and filtration of the aliquot after neutralisation gave the best result among the tests applied. The method was further modified by evaluating the suitable sample size, TCA volume and TCA concentration used as well as simplifying the moisture content application for fish meal. Other minor alterations were also suggested for both original and modified method at the preparation stage of diazotizing solution and absorption measurement.