Determination of the quality of liquid smoked tilapia fillets based on physicochemical analysis

Abstract

In an attempt to produce a convenient tilapia (Oerochromis nilotiucs) product with appealing sensory properties, cold liquid-smoking was applied to fish fillets followed by vacuum packaging. Based on biochemical and sensorial analysis, quality monitoring of forty fish samples was conducted over 60 days of refrigerated storage at 2 ± 1 °C. In smoked fillets, the levels of trimethylamine (0.4 to 2.73 mg/100 g) and total volatile bases (12.94 to 21.19 mg/100 g) remained below the threshold limits (10–12 mg/100 g and 30–45 mg/100 g respectively) over the entire period of storage. Among the analysed biogenic amines, only agmatine (23 mg/kg) increased significantly in smoked fillets reaching levels of (229 mg/kg). In parallel, hypoxanthine increased significantly (0.06 to 2.1 µmol/g) over storage. Electrophoretic analysis showed a significant change in sarcoplasmic and myofibrillar protein profiles in smoked fish fillets. The indices of atherogenicity (1.17) and of thrombogenicity (1.08) decreased significantly after spray-smoking to values of (0.7) and (0.6) respectively, without significant change during storage suggesting a stability of the fatty acids profile. Analysis of polycyclic aromatic hydrocarbons (PAHs) of fresh and smoked fillets showed undetectable level of benzo(a)pyrene (BaP) and the sum of 4 PAHs (chrysene, benzo(b)fluoranthene. benz(a)anthracene, Benzo(a)pyrene) (0.22 µg/kg) was far lower than the limit of acceptability (12 µg/kg). The determination of metal trace showed absence of cadmium (Cd) and lead (Pb) and low level of copper (Cu) (1.47 µg/g) in smoked fish fillets. Data submitted to principal component analysis (PCA) showed that cold spray-smoking maintained a good quality of fish fillets by preserving lipids and fatty acids specially PUFA (w3) degradation and by inhibiting bacterial growth as reflected by the reduced production of nitrogenous compounds.