Effects of Farming System on the Rheological Behavior of Rennet-Induced Coagulation in Milk from Skopelos Breed Goats

This study examined the impact of extensive and intensive farming systems on the rheological behavior of rennet-induced goat milk coagulation in the indigenous Greek Skopelos goat breed. Milk samples were obtained from Skopelos dairy goats reared under extensive and intensive farming systems at two farms in Greece. Rennet-induced coagulation kinetics (at 35 °C) and curd rheological properties were assessed using dynamic rheometry. Milk from the extensive system exhibited longer rennet coagulation time (RCT) but resulted in curds with higher storage modulus (G') and complex viscosity (η*), indicating formation of stronger coagulated structures compared to curds from the intensive system. The differences can be attributed to variations in milk composition and the structural characteristics of protein components, e.g., casein fractions, between the two systems. Principal component analysis (PCA) revealed that the farming systems could be differentiated based on the rheological properties of the curds, specifically on structure-related parameters (loss tangent, tanδ, apparent yield stress, τ_y). Strong correlations (p < 0.01) were noted between G'max and caseins/total proteins (positive), as well as with pH (negative), in both farming systems. These findings offer valuable insights into animal farming practices and cheese production, providing evidence of the relationships between goat-rearing systems and rheological properties of rennet-coagulated milk products.