Development of citrus peel by-product as a slice jam by using two-level factorial design

Natural slice jam from the citrus peel is a product that enhances the economic value of the waste of citrus fruit peel. The goal of the study was to improve a recipe for a natural jam made entirely from citrus peel and shaped into a square to make it a more convenient and ready-to-eat product. A two-level factorial design was used to investigate the effects of four independent variables; X1: concentration lemon peel (Citrus limonum), X2: concentration orange peel (Citrus sinensis), X3: storage temperature, and X4: sugar. Sample processing was performed at range between 10 and 20 g of lemon and orange peel concentration and sugar (6–10 g) at a constant gelatine weight of 1.6 g. The samples were stored at 2 °C and 25 °C, and textural properties (hardness and adhesiveness) were evaluated. Results indicated that concentrations of lemon peel (10 g), orange peel (15 g), sugar (8 g), and storage temperature (13.5 °C) significantly influenced jam texture. Interaction effects, including AD, BC, and BD, were notable. Optimal conditions favoured higher orange peel concentration. Validation experiments confirmed a maximum 10 g lemon peel concentration with an error below 10%. Despite room temperature storage causing textural quality deterioration due to syneresis, this study contributes valuable insights for food industry applications of natural products, greener and more cost-effective. The factorial design approach effectively optimized citrus peel slice jam formulation, demonstrating the significance of applied sciences in addressing practical challenges.