Impact of chitosan–thyme and chitosan–rosemary essential oil coatings on biochemical, oxidative, and volatile profiles of Turkish fermented sausage ‘sucuk’ during ripening

In the current study, the effects of chitosan coatings combined with thyme or rosemary essential oils (EOs), applied as natural antifungal agents to prevent superficial fungal growth on the surface of sucuk, were investigated throughout the ripening period in terms of lipolytic, proteolytic, and oxidative changes, as well as volatile composition and sensory properties. Six sucuk groups were produced by covering the casing surface on day 4 of production with distilled water (DW), acetic acid (AA), potassium sorbate (PS), chitosan (C), chitosan+thyme EO (CT), or chitosan+rosemary EO (CR). Superficial fungal growth was reduced approximately 4-log units in chitosan+EO treatments compared to the control. The lowest fungal count (log CFU/cm2) was observed in PS-treated sucuk (0.60), followed by CT (2.06) and CR (2.09), whereas this value was 5.95 in the DW group (p<0.05). Coatings containing EOs retarded lipid oxidation as well as free fatty acid (FFA) formation, as the lowest values were recorded in the CT and CR groups, with FFA contents of 4.75% and 4.96% and thiobarbituric acid reactive substances values of 0.60 and 0.60 mg MA/kg, respectively. The lowest sulfhydryl reduction (32%) was also observed in the CT and CR groups, compared to the PS, in which the reduction was 39% (p<0.05). The fatty acid profile and sensory properties of the sausages were not adversely affected by the superficial chitosan–EO coatings. A total of 46 and 67 volatile compounds were identified in sausages and casings, respectively. The major volatile constituents of sucuk in the CT and CR groups were acids, terpenes, sulfur compounds, and aldehydes, accounting for 10.41–17.07%, 58.89–66.88%, 5.36–6.70%, and 12.68–12.85% of the total volatile composition, respectively. In conclusion, CT or CR coating can be considered an alternative antifungal approach to synthetic treatments for preventing superficial fungal growth without adversely affecting the characteristic quality properties of sucuk. © The Author(s) 2026