Antimicrobial activity of grass kelp macroalgae (Ulva intestinalis) hydro-alcoholic extract on cultured Beluga (Huso huso) minced fish during refrigerated storage

This study was carried out to investigate the possibility of using Ulva intestinalis macroalgae extract as a natural antibacterial agent in Beluga minced meat. For this purpose, the minimum of inhibitory concentration (MIC) of the hydroalcoholic extract of the algae was determined in vitro by micro-well dilution method against Listeria monocytogenes pathogen. Then, the concentrations of controls (without any additive), BHT (as a synthetic antioxidant), MIC, 2 fold of the MIC (2MIC) and 3 fold of the MIC (3MIC) concentrations, were mixed with minced meat and refrigerated. Microbial properties of the samples including psychrophilic bacteria count, mesophilic bacteria count, Pseudomonas count and Enterobacteriaceae count were measured at 0, 4, 8, and 12 days. According to the results, the MIC was 12.5 mg/mL. The result of this study showed that the samples with the algae extract had less microbial load in comparison with control and BHT groups (p <0.01). Also, 3MIC showed the most antibacterial effect among other algae extract treatments by the lowest amount of mesophilic bacteria (6.27 Log cfu/g), cold (09.08 Log cfu/g) Pseudomonas (6.6 Log cfu/g) and Enterobacteriaceae (6.21 Log cfu/g) population size at the end of storage period. The results indicated that grass kelp macroalgae is a suitable species for use as a natural preservative, and the minced fish with three fold of the MIC concentration had less bacterial spoilage during the storage period in a refrigerator.