# Trends and Opportunities in the Dairy Industry: A2 Milk and Processing Methods
## 4 A2 Milk
### \(\beta\)-Caseins A1 and A2--The Differences
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Study Subject** & & **Results A1** & & **Results A2** & **Ref.** \\ \hline Acid and rennet coagulation & \(\bullet\) & Less firm curd & \(\bullet\) & Slightly higher acid gel density, rennet aggregation rate to control milk (A1A1 + A1A2 blend) \\ \hline Acid and rennet coagulation & \(\bullet\) & Acid and enzymatic coagulation times were the same for A1 and A2 & [9] \\  & \(\bullet\) & No differences in the fermentation curves & \\  & \(\bullet\) & No significant differences in the water holding capacity & \\  & \(\bullet\) & Comparable acid and rennet coagulation properties—creating dairy products in a similar way with both milk types where possible & \\ \hline Rennet coagulation and cheese making & \(\bullet\) & Lower protein and higher fat content in prepared Cheddar cheese & \(\bullet\) & Poorer rennet coagulation \\  & \(\bullet\) & Cheese was softest, most fracturable than A2A2 (hardest, last fracturable) and A1A2 samples & \(\bullet\) & Higher protein and lower fat content in prepared cheese \\  & \(\bullet\) & Proteolysis was not found to differ & \\  & \(\bullet\) & Cohesiveness difference was not found in cheese ripened for 180 days & \\ \hline Impact of heating & \(\bullet\) & Higher presence of aggregated structures after heating & \\  & \(\bullet\) & Histidine present in A1 is involved in the formation of dehydroalanine & \(\bullet\) & Composed of larger casein micelle particles \\ \hline Cheese yield, curd nutrient recovery, whey composition, and cheese composition & \(\bullet\) & The efficiency of nutrient recovery from whey was higher for samples with mainly A1 beta-casein & \(\bullet\) & An increase in the \(\beta\)-casein A2 content of milk has been linked to lower cheese yields \\ \hline composition & \(\bullet\) & No differences in the final cheese composition & \\ \hline Calcium distribution, acid gelation, foaming properties, and microstructure of acid gels & \(\bullet\) & Shorter time for gelation & \(\bullet\) & Higher proportion of free ionic calcium, enhanced foam formation capability \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of A1 vs. A2 milk. Figure 2: The difference between the amino acid chain of A1 and A2 casein [56]. The technological differences between A1 and A2 milk indicate that A2 milk proteins may form less compact cards than those found in conventional milk products, which is associated with the finer structure of the cheeses and cards obtained in this way. In addition, differences in coagulation time are apparent between A1 and A2 milk (longer in the case of A2), which, for technological reasons, must be thoroughly investigated. The impact of heating showed that A1 milk had a higher presence of aggregated structures and histidine involved in dehydroalanine formation, while A2 milk consisted of larger casein micelle particles. However, the available database of publications does not allow firm conclusions to be drawn due to the significant variation in milk samples, the characteristics of which depend on many factors (among others, breed of cows, housing conditions, and season) and from which some of the differences noted to date may result. It is important to note that sensory characteristics showed no negative perception of A2 milk.