MICROBIOLOGICAL QUALITY ASSESSMENT OF RAINBOW TROUT (ONCORHYNCHUS MYKISS) MEAT TREATED WITH ROSEMARY AND THYME DRIED HERBS AND ESSENTIAL OILS

Abstract

This study investigates the effects of thyme and rosemary dried herbs, as well as thyme and rosemary essential oils (1%, w/v), on the microbiological quality of vacuum-packed rainbow trout meat stored under refrigerated conditions (4 ± 1 °C) for 7 days. The microbiological quality of meat was monitored based on total viable counts, coliform bacteria, and lactic acid bacteria counts over a designated storage period (on the 0^th, 1^st, 3^rd, 5^th and 7^th day of storage). As expected, the highest total viable counts were observed on the 7^th day of storage in the untreated aerobically packed control group reaching 5.723 ± 0.021 CFU.g^-1. The tested treatments showed potential in reducing the growth of bacteria in rainbow trout meat samples. Across all bacterial groups under investigation, rosemary essential oil appears to have the most advantageous effect in inhibiting bacterial growth compared to other tested treatments. Cultivated isolates were identified by MALDI-TOF mass spectrometry and assigned to 33 species belonging to 14 families. The most prevalent family was Enterobacteriaceae (18.99%), and the most abundant species found in samples was Hafnia alvei (8.86%). Our findings suggest the potential of using thyme and rosemary in both essential oil and dried forms as natural preservatives to enhance the microbiological quality and longevity of refrigerated rainbow trout meat.