Effect of aS1 casein level on stretchability of goat curd

Protein genetic variants of goat milk have been studied for more than 40 years and it is known that αs1-CN presents a remarkable variability that is also connected to different level of synthesis. In fact, dairy goats can present a low, medium or high αs1-CN content connected to more than 10 different genetic variants influencing the expression of this protein fraction. These genetic variants affects both the milk composition and the coagulation properties. In fact, fat globule size and the presence of the polar lipids varies based on αs1-CN content; larger fat globule and low polar lipids are connected to high amount of this protein. Several studies reported a correlation between the milk coagulation properties and αs1-CN content, with shorter coagulation time in the presence of low level but firmer curds in conjunction with high level. Recently, protocols for manufacturing high moisture mozzarella from goat milk have been developed, but no investigation has been performed on the stretching behaviour of goat milk in comparison with cow milk. The present work resumes the outcomes of a study carried out in Apulia and Basilicata Region, aimed at finding goat milks with different profiles of αs1-CN and evaluating the stretching properties of the curd derived therefrom. Electrophoresis was used for casein characterization and Texture Profile Analysis (TPA) for evaluating the stretching properties. More than 30 milk samples were collected and three of them used for the cheesemaking trials al laboratory level. The results of TPA revealed significant differences in the stretching properties in connection with the αs1-CN profile. This study shed light on the stretching properties of goat milk and could be useful for dairy manufacturers for standardizing the protocols for the production of goat pasta filata cheeses.