Fluorescent compounds formation during sardine (Sardina pilhiardus) chilling: Comparison with lipid damage indexes

Abstract

Sardine was stored at 0°C on ice during 16 days. During this time the fluorescent compounds formation was studied at different wavelength maxima in order to assert quality changes; fluorescence analyses were undergone on the aqueous and organic (lipids) phases resulting from the lipid extraction. Quality measures of lipid hydrolysis (free fatty acids content, FFA) and oxidation (conjugated diene formation and thiobarbituric acid, TBA, test) were also carried out. Traditional indexes of lipid damage did not assert deterioration in the case of advanced damage. Diene content reflected and increasing value till the day 9 of storage, and then a continuous decrease. Further, FFA content and TBA test showed the highest values on the day 13 of storage, followed by a slight decrease. An increase in fluorescence content was observed in most of the excitation/emission maxima studied (393/463 nm, 446/490 nm and 479/516 nm), at the time that others decreased (327/415 nm, specially); as an overall result, a relative increase in the maxima of higher wavelength was observed in comparison with the lower ones. The ratio between two of the fluorescence maxima analyzed (393/463 nm and 327/415 nm) exhibited an overall increase respect to the time of chilled storage. The study of this ratio in the aqueous extract showed a better correlation (r= 0,8533) than in the case of the organic one (r= 0,7457). From the present results, it is concluded that the interaction compounds determination by mean of their fluorescent properties is useful as a damage measure during the chilled storage.