EFFECT OF PH ON FLUORESCENCE FORMATION RELATED TO FISH DETERIORATION

Earlier studies have investigated fluorescence at different excitation /emission maxima during common types of fish processing. A shift towar ds higher wavelength maxima was observed and measured as the ratio bet ween two of the maxima tested. This fluorescence ratio (delta F) corre lated with increased fish damage. The present work is focused on the e ffect that pH can have on the formation of fluorescent compounds in fi sh muscle systems. Minced hake muscle was homogenised with 0.1 M phosp hate buffer of different pH values (5, 6, 7 and 8) and was stored at 3 0 degrees C for up to 30 days. Lipid damage, measured as the delta F v alue of the aqueous reaction medium and the fish lipid extract, indica ted little difference between the effect of different pH values under the conditions employed in the present experiment. The effetct of form aldehyde (FA) in the same reaction medium was also evaluated. It was o bserved that FA had a positive effect on the fluorescence shift occurr ing in the aqueous reaction medium, so that a higher delta F value was observed for pH7 and pH 8, especially for the latter. It is concluded that changes in the delta F value during fish storage and/or processi ng are of special interest as? in addition to FA formation and lipid o xidation, significant pH increases are expected to occur as a result o f damage.