Texture-Modified Black Plum Peel Marmalade for Older Adults: RSM-Based Optimization of Chemical and Rheological Properties

Background: This research was conducted with the aim of optimizing the formulation of black plum peel marmalade, in order to obtain a product with a modified texture suitable for consumption by the elderly. In this regard, the effect of independent variables of pectin and puree concentration on the chemical, and rheological properties of the formulation was investigated.
Methods: Formulation modeling and optimization was done using response surface method. Pectin and puree concentration as independent input variables and 7 indicators including pH, acidity, moisture content, ash, apparent viscosity, flow behavior index (𝑛), consistency coefficient (𝐾), were defined as response variables. Simultaneous optimization of responses was done using the desirability function.
Results: Numerical optimization identified the optimum formulation at coded levels A = 0.45% (pectin) and B = 40.17% (black plum peel puree) with overall desirability 𝐷=0.70. At this optimum point, the predicted values for pH, acidity, moisture content, apparent viscosity, flow behavior index, and consistency coefficient were 3.43, 0.30%, 33.88%, 210.559 Pa·s, 0.27, and 88.33 Pa·sⁿ, respectively. The regression models provided useful descriptions of several responses; however, some models showed limited predictive performance, as indicated by low or negative Pred-R² values.
Conclusion: The results showed that the optimized formulation of black plum peel marmalade provides suitable chemical characteristics and rheological properties for swallowing and consumption by the elderly. Therefore, the use of black plum peel is not only an efficient solution to reduce food industry waste and create added value, but can also be used as a practical raw material in the development of texture-modified products for target groups with swallowing limitations.