"A2 milk" authentication using isoelectric focusing and different PCR techniques.

Area of Science:

• Animal Genetics and Breeding
• Food Science and Technology
• Biochemistry and Molecular Biology

Background:

• Genetic variants of milk proteins, particularly beta-casein, are significant for milk composition and technological properties.
• The A1/A2 hypothesis suggests beta-casein variant A1 may pose health risks, unlike beta-casein A2, due to beta-casomorphin-7 release.

Purpose of the Study:

• To adapt and establish analytical methods for identifying beta-casein genetic variants.
• To enable reliable differentiation of common beta-casein variants (A1, A2, B, C, A3) and homozygosity for A2.

Main Methods:

• Isoelectric focusing of milk proteins.
• Allele-specific polymerase chain reaction (AS-PCR) for differentiating variants A1, A2, B, and C.
• Amplification-created restriction site (ACRS)-PCR for detecting variant A3.
• Restriction fragment length polymorphism (RFLP)-PCR for discriminating A2 (homozygote/heterozygote) from non-A2 animals.

Main Results:

• AS-PCR reliably differentiated common beta-casein variants.
• ACRS-PCR successfully detected variant A3.
• RFLP-PCR accurately distinguished A2 from non-A2 animals.
• Traces of beta-casein A1 were detected in commercial 'A2 milk' in Austria.

Conclusions:

• Established PCR-based methods provide reliable identification of beta-casein genetic variants.
• Genotyping dairy cows and screening commercial products are recommended to ensure 'A2 milk' authenticity and prevent fraud.
• Consumer protection from unexpected beta-casein variant presence in 'A2 milk' is essential.