Assessment of antioxidant effectiveness on thermally treated marine lipids by fluorescence detection

Previous research has studied fluorescence development during fish processing. As a result, a bathochromic shift towards higher wavelength maxima was detected and employed successfully as a way of measuring quality changes. In the present work, the same fluorescence analysis was tested for assessing the preservative effect of an antioxidant compound on thermally treated marine lipids. Two kinds of marine lipid systems (cod liver oil and horse mackerel white muscle) were heated for different times (up to 15 days), under different temperatures (15 degrees C, 30 degrees C, 50 degrees C) and with different antioxidant (citric acid) contents (0.01-0.50% in the oil systems, w/w; 0.10-1.00% in the fish muscle systems, w/w). Fluorescence results showed an antioxidant effect at all the temperatures studied; at 50 degrees C the presence of citric acid produced a significant decrease of the bathochromic shift of fluorescence in both the oil and the fish muscle systems when present in the following concentrations ranges: 0.10-0.50% and 0.40-1.00%, respectively. The antioxidant effect of citric acid was also confirmed by traditional browning development (420 nm) analysis. Good linear correlations were obtained for both fluorescence and browning values for the reaction time at all the temperatures tested. It is concluded that fluorescence analysis could be successfully employed as an accurate tool when studying the effect of antioxidant compounds during marine product manufacture, especially in cases where interaction compounds between lipid oxidation products and nucleophilic constituents are prone to be formed.