Evaluation of the Effect of Dracocephalum moldavica Mucilage and Nanoemulsion of Satureja hortensis Essential Oil Edible Coating on Microbial, Chemical, and Organoleptic Properties of Rainbow Trout Fish Fillet at Refrigerator Temperature.

This study evaluated the use of an edible coating made from Dracocephalum moldavica seed mucilage with Satureja hortensis essential oil emulsion and nanoemulsion to extend the shelf life as well as preserve the sensory qualities of rainbow trout fillets. Fillets were split into four groups: uncoated (CON), 1% D. moldavica mucilage coating (M), mucilage coating containing 2% S. hortensis EO (M + EO), and mucilage coating containing 2% nanoemulsion of S. hortensis EO (M + NEO). After coating, the fish fillets were assessed for microbial (Total Viable Count, psychrotroph, coliform, Staphylococcus aureus, Lactic Acid Bacteria, and yeast and mold), chemical (pH, Total Volatile Basic Nitrogen, and Thiobarbituric Acid Reactive Substances) and organoleptic (taste, color, texture, odor, and overall acceptability) properties at specified intervals (0,2,4,7 days). Carvacrol (40.23%), p-cymene (24.42%), and γ-terpinene (21.76%) were the principal compounds of S. hortensis EO. The nanoemulsion showed an average particle diameter of 135.6 ± 3.81 nm and a zeta potential of -51.26 ± 1.70 mV. Throughout the study, no significant difference was observed between the CON and M groups, but significant differences were found between these two groups and the M + EO as well as M + NEO groups (p < 0.05), leading to an extension of shelf life by more than 3 days. The findings of the chemical tests revealed a similar trend to the microbial results, indicating a significant difference between the CON as well as M group and the groups containing the emulsion and nanoemulsion of S. hortensis EO. Sensory scores diminished over time but were best maintained in the nanoemulsion-coated samples. According to the results of the present study, the edible coating of D. moldavica seed mucilage containing the emulsion and nanoemulsion of S. hortensis EO can be employed to enhance the shelf life of rainbow trout fillets.