Optimization of Juice- and Poultry-Industry By-Product Incorporation in Cooked Sausage Formulations Using Response Surface Methodology

Sustainability concerns are driving greater interest in valorizing agri-food by-products as ingredients in meat products. This study aimed to optimize a cooked turkey sausage formulation incorporating apple pomace powder (APP), turkey skin (TS), and iced water (IW) and to evaluate their effects on physicochemical, textural, and sensory properties. Response surface methodology (RSM) was applied with APP (1–5%), TS (20–30%), and IW (15–30%) as independent variables. The responses evaluated were pH, cooking yield, color parameters (L*, a*, and b*), hardness, and overall acceptability. Numerical optimization identified a formulation containing 4.45% APP, 23.19% TS, and 15.73% IW, with predicted values of pH 5.63, cooking yield 87.21%, lightness (L*) 73.78, redness (a*) 4.81, yellowness (b*) 11.35, hardness 51.21 N, and overall acceptability 6.59. Experimental validation showed that the measured responses were generally consistent with the RSM predictions, although a larger deviation was observed for b*. Principal component analysis (PCA) showed that PC1 and PC2 explained 51.66% and 28.89% of the total variance, respectively, accounting for 80.55% cumulatively. PCA provided an exploratory representation of relationships among the measured responses, with PC1 primarily contrasting pH and lightness with cooking yield, redness, and yellowness, while hardness and overall acceptability were more strongly associated with PC2. Overall, the results demonstrate the feasibility of incorporating APP and TS into cooked turkey sausage and identify an optimized formulation that balances by-product incorporation with physicochemical, textural, and sensory responses.