Effects of extracted propolis ( Apis mellifera ) on physicochemical and microbial properties of rainbow‐trout fish burger patties

Abstract

Freeze-drying of propolis (FDP) obtained from ethanol extraction of raw propolis enhanced its total phenolic and reduced effective concentration (EC50) substantially >95% and 99%. Then the ground fish of rainbow-trout was mixed with different (0.1, 0.2 and 0.4%) levels of FDP to make frozen fish burger (FFB), and analyzed for physicochemical and microbial characteristics on 0-, 30-, 60-, and 90-days of −18°C storage. While the PV, TBA, TVN-B, and overall color changes (∆E) of FFB with highest FDP increased only ~30, 120, 25%, and 7.3 unit, they increased in control sample up to 90, 183, 40%, and 13.1 unit after 90-days frozen storage. Whereas the cooked FFB patties (containing 0.4% FDP) had significantly higher cooking yield, its fat and moisture retentions were considerably more than the control sample. Additionally, its colony forming unit (CFU) for Staphylococcus aureus, coliform, yeast, and mold counts were 1,040, 219, and 19.3 times less than the control. Novelty impact statement Freeze-drying of propolis (FDP) after ethanol extraction of raw propolis improved its TPC (total phenolic content) and reduced its effective concentration (EC50) substantially more than 95% and 99%. Addition of FDP to rainbow-trout fish burger patties significantly reduced its deteriorative chemical indexes (PV, TBARS, TVN-B), and microbial loads for 3 months storage at −18°C. Combining of FDP with fish burger patties (at 0.4 g/100 g) could significantly increase its cooking properties (extra yield and more retentions of fat and moisture) even after 90-day of frozen stowage.