Optimization of a local Ficus carica plant-based coagulant for fresh goat milk transformation in southern Tunisia

Milk coagulation represents the fundamental phase-separation unit operation in cheesemaking, determining both the final yield and curd quality. This study optimized the enzymatic coagulation process of high-solids goat milk (16.3% total solids) from the Arab breed, indigenous to the arid climate of southern Tunisia, using a local plant-based coagulant from Ficus carica latex. A three-factor, three-level Box-Behnken Design (BBD) was employed to evaluate the simultaneous effects and interactions of temperature (40-60 °C), coagulant dosage (2-4 mL/50 mL milk), and latex dilution (0-75%). The experimental results were modeled using a second-order polynomial equation, and the model's adequacy was confirmed via Analysis of Variance (ANOVA). A complex three-way interaction was identified, particularly highlighting a "yield valley" at intermediate factor levels. This phenomenon is attributed to a kinetic imbalance between the enzymatic proteolysis and the protein aggregation phases, modulated by the hydration state of the enzyme. Optimization was successfully achieved, identifying the conditions required to maximize cheese yield while overcoming the high buffering capacity of the high-solids goat milk. These findings provide a technical framework for the valorization of local dairy and botanical resources in arid regions.