Quantitative determination of αs1–casein in goat’s milk using reversed-phase high performance liquid chromatography (RP–HPLC)

The chemical, technological and allergy properties of goat’s milk are significantly affected by the level of αs1-casein. Despite indications that more than 90% of cow’s milk protein allergy (CMPA) children reacted similarly to goat's milk in typical IgE-mediated forms, the availability of goat's milk without αs1-casein appeared to be a potential alternative for patients with cow's milk allergy. In Malaysia, there is a lack of quantitative data on αs1-casein in raw and commercial goat’s milk. To address this problem, this study aimed to quantify αs1-casein in goat’s milk using reversed-phase high performance liquid chromatography (RP–HPLC). The procedure was developed using a total of twenty samples comprised of commercial and raw goat’s milk. For the calibration curve, a linear relationship with R² > 0.999 was obtained using cow’s α-casein standard and peak areas were observed over the concentration range, with a limit of detection (LOD) of 0.025 mg/ mL and limit of quantification (LOQ) of 0.075 mg/mL, respectively. The amount of αs1- casein in the twenty samples ranged from 0.08±0.01 to 1.45±0.17 mg/mL. Three samples which were claimed as goat’s milk infant formula were not found to contain αs1-casein. Repeatability and reproducibility were satisfactory for both retention times and peak areas. The RSD of peak areas ranged from 0.01 - 8.07% within an analytical day and from 0.61 - 1.77% across analytical days. This study will contribute as a reference method for analysis and surveillance data of αs1-casein, in private or national laboratories, as well as milk and milk product manufacturers.