The Use of Bioactive Extracts from Fish By-Products in Improving Microbiological Stability of Fish Based Food

Fish is a food of high nutritional value, being an important source of proteins, fat, vitamins, and essential minerals. Atlantic horse mackerel is also rich in omega-3 polyunsaturated fatty acids (n3-PUFAs), recognized for their benefits to cardiovascular and neurological health. However, this composition also makes it highly susceptible to lipid oxidation, reducing its shelf life. Oxidation is accelerated by high water activity and near-neutral pH, conditions common in fish and processed products such as fish burgers. This work aimed to develop fish burgers incorporated with bioactive extracts (protein hydrolysates from cod fish processing by-product—PH, or green tea extract—GTE) and study their shelf life. The PH was recovered from cod frames using subcritical water extraction, and GTE with hydro-alcoholic extraction. The fish burgers were prepared using minced fish meat incorporated with 1% (w/w) of extracts, in four formulations: (i) 1% (w/w) of PH; (ii) 1% (w/w) of GTE; (iii) a combination of both extracts at 0.5% (w/w) each; and (iv) control without extracts. Physical–chemical, antioxidant and microbiological analysis of the burgers was performed to evaluate their preservation over 6 days of refrigerated storage. Compared to the control, samples with only GTE or the combined GTE + PH presented a delay in oxidation (50% less in TBARS) and microbiological deterioration (reduction of 0.5–1.8 Log CFU/g in total psychrotropic microorganisms). No significant changes were observed in the fish burgers incorporated with only PH. The results demonstrate that the incorporation of bioactive extracts has potential in reducing oxidative degradation and improving microbiological stability in fish-based products; however, superior doses must be used. Moreover, the use of natural extracts aligns with current consumer demand for clean-label and functional foods.