Canned fruits and vegetables generally have a high acidity and salinity content, in order to prevent the product from spoiling, in addition to enhancing its flavor.
The cream-based sauce started to curdle due to the acidity present in the canned tomatoes.
By lowering the pH of dairy products, a protein in them called casein begins to clot. It is this clotting of the casein that causes the cream-based sauce to curdle.
