The effect of carvacrol-containing nanofiber packaging on the shelf life of bread

The incorporation of natural antimicrobial compounds into biodegradable polymers for food packaging has gained considerable attention due to its dual role in enhancing food safety and promoting environmental sustainability. In this context, the present thesis investigates the effect of different concentrations of carvacrol (10%, 20%, and 30%) incorporated into polylactic acid (PLA)-based nanofiber packaging systems on the shelf life of bread. Nanofibers were produced via electro-blown spinning and combined with oriented polypropylene (OPP) films to create active packaging materials, which were then applied to bread slices. Control samples included only OPP film and PLA nanofibers without carvacrol. The study comprehensively evaluated the structural, physical, mechanical, and functional properties of the nanofibers and examined the microbiological stability, chemical composition, pH, and color changes in the packaged bread samples. FTIR analysis confirmed the preservation of PLA's characteristic ester structure and indicated physical interactions between carvacrol and the polymer matrix, as evidenced by minor shifts in the carbonyl group peaks. Mechanical tests showed that increasing carvacrol content led to decreases in bursting strength and tensile resistance, while heat seal strength significantly increased—suggesting a plasticizing effect of carvacrol on the PLA matrix. Water vapor permeability tests revealed enhanced barrier properties with higher carvacrol concentrations, with the lowest permeability observed in the 30% carvacrol sample. Antioxidant activity determined by the DPPH method increased proportionally with carvacrol concentration, and the 30% carvacrol sample exhibited the highest radical scavenging capacity. Microbiological analyses showed no yeast development in any group, while mold growth decreased significantly with increasing carvacrol levels. On day 15, mold growth was limited to only 1 CFU/g in the 20% and 30% carvacrol samples, whereas the control group exceeded 3000 CFU/g. Chemical analyses revealed no substantial variations in moisture, ash, fat, or protein content across the groups. Color analysis indicated a slight increase in yellowness (b*) with higher carvacrol levels, while pH values remained more stable in carvacrol-treated samples, reflecting suppressed microbial activity. The findings demonstrate that PLA-based nanofiber packaging enriched with carvacrol offers a promising natural and biodegradable solution for extending the shelf life of perishable food products such as bread. These systems not only provide effective antimicrobial protection but also contribute to the development of sustainable food packaging technologies.