On food and cooking the science and lore of the kitchen ( PDFDrive ) 1193

separating, or the proteins coagulating and curdling Whole milk is only about 4% fat, so its fat globules are too few and far between to block the flow of the water phase and give much of an impression of thickness Cream is a portion of milk in which the fat globules have been concentrated and crowded: light cream is around 18% fat, and heavy or whipping cream around 38% In addition to its fat supply, cream offers proteins and emulsifying molecules that can help stabilize other, more fragile emulsions (beurre blanc) Heavy Cream Resists Curdling The casein proteins in milk and cream are stable to boiling temperatures, but they’re sensitive to acidity, and the combination of heat and acid will cause them to curdle Many sauces include flavorful acid ingredients: sauté pans are often deglazed with wine, for example This means that most milk and cream products, including light cream and sour cream, can’t actually be cooked to make a sauce; they must be added as a last-minute enrichment The exceptions are heavy cream and crème frche, which contain so little casein that its curdling simply isn’t noticeable (p 29) Reduced Cream When heavy cream is added to another liquid to enrich and thicken it — to a meat sauce, or deglazing liquid, or a vegetable puree — then of course its fat globules are diluted and its consistency thins down In order to make cream a more effective thickener, cooks concentrate it even further by boiling off water from the continuous phase When the volume of cream is reduced by a third, the globule concentration reaches 55% and the consistency is like that of a light starchthickened sauce; when reduced by half, the globules take up 75% of the volume and ... by a third, the globule concentration reaches 55% and the consistency is like that of a light starchthickened sauce; when reduced by half, the globules take up 75% of the volume and ... diluted and its consistency thins down In order to make cream a more effective thickener, cooks concentrate it even further by boiling off water from the continuous phase When the volume of cream... including light cream and sour cream, can’t actually be cooked to make a sauce; they must be added as a last-minute enrichment The exceptions are heavy cream and crème frche, which contain so little