The effect of pomegranate peel extract on Salmonella Typhimurium in a nisin containing chicken meat model

Although chicken meat has high nutritional value, it has a short shelf life under refrigerated conditions. Salmonella Typhimurium is the most common foodborne pathogen associated with chicken products. To extend shelf life and reduce microbiological risk, natural antimicrobial and antioxidant compounds are preferred. Pomegranate peel extract, which is rich in phenolic compounds, is an important byproduct in this regard and has been shown to exhibit antimicrobial activity. However, the effectiveness of nisin against Gram-negative bacteria is limited due to the lipopolysaccharide layer in their cell walls. In this thesis, the antimicrobial potential of nisin which has limited activity against Gram-negative bacteria combined with pomegranate peel extract under frozen storage conditions against S. Typhimurium was investigated. In addition, the effects of nisin and pomegranate peel extract on product quality and lipid oxidation in a chicken meat model were examined. This study was conducted in three work packages. In the first work package, a Box-Behnken experimental design was applied to determine the extraction conditions of the pomegranate peel extract to be used. Based on the obtained conditions, disk diffusion analyses were performed, and the group showing the highest antimicrobial activity was selected for optimization. In the second work package, experimental groups containing nisin and pomegranate peel extract were evaluated in terms of product quality and lipid oxidation. The chicken meat model was cooked in an oven until its core temperature reached 75 °C and stored at 4 °C for 7 days. During storage, cooking loss, pH, color, texture profile, TBARS, total aerobic mesophilic, coliform, and psychrophilic bacterial counts were measured to assess the effects of the additives on quality and oxidation. In the final work package, the effectiveness of nisin and pomegranate peel extract in a raw chicken meat model under frozen storage conditions was evaluated. The products were stored for 90 days, and water activity, pH, and S. Typhimurium counts were determined at specific intervals. The obtained data revealed the effects of the additives on microbiological stability and product safety. As a result of this study, the highest antimicrobial activity during the optimization phase was obtained at a 10% ethanol/water ratio and 25% pomegranate peel concentration. In the raw chicken meat model, the group containing 1% pomegranate peel extract exhibited the greatest inhibition against S. Typhimurium, with a reduction of 1.74 log₁₀ CFU/g. In groups containing pomegranate peel extract, total aerobic mesophilic bacterial growth was inhibited from the first day of storage, and lipid oxidation was lowest in the group containing 2% pomegranate peel extract and nisin. Furthermore, groups containing pomegranate peel extract showed lower L* color values and decreased pH. In texture profile analysis, hardness was highest in the group containing 2% pomegranate peel extract and nisin, while elasticity values decreased in the extract-containing groups. Overall, the results demonstrate that the combined use of pomegranate peel extract and nisin reduces S. Typhimurium risk and lipid oxidation in chicken meat products, while positively affecting quality parameters such as color and texture.