Effect of pomegranate (Punica granutum) and rosemary (Rosmarinus officinalis L.) extracts on shelf-life for chilled Greenland halibut (Reinhardtius hippoglossoides) fillets in modified atmosphere packaging at 2 ºC

The present study evaluated the effect of pomegranate extract (1% v/w) and rosemary extract (1% v/w) as natural preservatives as well as their combination (1% v/w) on shelf life extension of previously frozen and chilled Greenland halibut fillets in modified atmosphere packaging (MAP, 40%CO2/60%N2) at 2 °C. Parameters that were monitored were: microbiological (aerobic plate counts (APC), lactic acid bacteria (LAB), Lactobacillus spp., and Photobacterium phosphoreum), biochemical (pH, thio-barbituric acid (TBA), trimethylamine (TMA) and total-volatile-nitrogen (TVN)), and sensory (color, flavor and texture) attributes. For microbiological results, irrespective of treatments, APC reached levels ≥107 CFU/g during storage. The spoilage microflora of fillets in MAP was dominated by LAB, but the concentration of Lactobacillus was very low. During storage, P.phosphoreum was not detected in any sample. Among the chemical indices examined, TBA values of control samples exceeded the limit of 2 mg malondialdehyde (MDA)/kg (2.78 and 4.08 mg MDA/kg) on days 18 and 23 of storage, respectively, while TBA values for samples treated with extracts remained below the limit throughout the storage period. Final (TMA) and (TVN) values for all treatments ranged between 0.15 to 0.37 mg N/100 g and 16.90 to 24.10 mg N/100 g after 23 days of storage, respectively, not exceeding upper acceptability limit set by EU. Sensory analysis correlated well with TMA and TVN analysis, indicating a shelf life of longer than 23 days for all samples. The research was supported by the Federation of European Microbiological Societies (FEMS) and performed during a research visit by İlke Uysal Ünalan at DTU Food.