Abstract:

The effect of oregano essential oil (OEO) from Origanum heracleoticum L. on the quality and shelf life of
Oreochromis niloticus × O. mossambicus was studied. Five treatments were included in this trial, a control diet (OEO0) and
four other diets (OEO250, OEO500, OEO1 000 and OEO2 000) with 250, 500, 1 000 and 2 000 mg/kg of oregano essential oil,
respectively. After 20 weeks of experimentation, the fish were stored on ice at 4 ℃ for 0, 7, 14 and 21 days, respectively.
Physicochemical, microbiological and sensory analyses were carried out at each sampling point to determine the degree of
deterioration. A dose-dependent effect was observed on the color, TBARS and TVB-N during the storage. Microbiological
counts were lower for Enterobacteriaceae and coliforms at higher doses of oregano essential oil. The sensory analysis
showed no significant correlation between overall sensory quality of fish and oregano essential oil dose. The experimental
diets extended the shelf life of Oreochromis niloticus× O. mossambicus from 16 to 18 days compared with the control diet,
without significant correlation with dose.

Key words: Origanum heracleoticum L., dietary supplements, Oreochromis niloticus ×, O. mossambicus, shelf life