Modern Pastry and Plated Dessert Techniques is one of a series of Culinary Arts books developed to support the training of students and apprentices in British Columbia\u2019s food service and hospitality industry. Although created with the Professional Cook and Baker programs in mind, these have been designed as a modular series, and there for can be used to support a wide variety of programs that offer training in food service skills.<\/p>\n
Coagulation<\/a> is defined as the transformation of proteins from a liquid state to a solid form. Once proteins are coagulated, they cannot be returned to their liquid state. Coagulation often begins around 38\u00b0C (100\u00b0F), and the process is complete between 71\u00b0C and 82\u00b0C (160\u00b0F and 180\u00b0F). Within the baking process, the natural structures of the ingredients are altered irreversibly by a series of physical, chemical, and biochemical interactions. The three main types of protein that cause coagulation in the bakeshop are outlined below.<\/p>\n Eggs contain many different proteins<\/a>. The white, or albumen, contains approximately 40 different proteins, the most predominant being ovalbumin<\/a> (54%) and ovotransferrin<\/a> (12%). The yolk contains mostly lipids (fats), but also lipoproteins. These different proteins will all coagulate when heated, but do so at different temperatures. The separated white of an egg coagulates between 60\u00b0C and 65\u00b0C (140\u00b0F and 149\u00b0F) and the yolk between 62\u00b0C and 70\u00b0C (144\u00b0F and 158\u00b0F), which is why you can cook an egg and have a fully set white and a still runny yolk. These temperatures are raised when eggs are mixed into other liquids. For example, the coagulation and thickening of an egg, milk, and sugar mixture, as in custard, will take place between 80\u00b0C and 85\u00b0C (176\u00b0F and 185\u00b0F) and will start to curdle at 88\u00b0C to 90\u00b0C (190\u00b0F and 194\u00b0F).<\/p>\n Casein, a semi-solid substance formed by the coagulation of milk, is obtained and used primarily in cheese. Rennet, derived from the stomach linings of cattle, sheep, and goats, is used to coagulate, or thicken, milk during the cheese-making process. Plant-based rennet is also available. Chymosin<\/a> (also called rennin) is the enzyme used to produce rennet, and is responsible for curdling the milk, which will then separate into solids (curds) and liquid (whey).<\/p>\n Milk and milk products will also coagulate when treated with an acid, such as citric acid (lemon juice) or vinegar, used in the preparation of fresh ricotta, and tartaric acid, used in the preparation of mascarpone, or will naturally curdle when sour as lactic acid develops in the milk. In some cases, as in the production of yogurt or cr\u00e8me fra\u00eeche, acid-causing bacteria are added to the milk product to cause the coagulation. Similarly, tofu is made from soybean milk that has been coagulated with the use of either salt, acid, or enzyme-based coagulants.<\/p>\n Two main proteins are found in wheat flour: glutenin and gliadin (smaller quantities are also found in other grains). During mixing and in contact with liquid, these two form into a stretchable substance called gluten<\/a>. The coagulation of gluten is what happens when bread bakes; that is, it is the firming or hardening of these gluten proteins, usually caused by heat, which solidify to form a firm structure.<\/p>\n","protected":false},"excerpt":{"rendered":"Egg proteins<\/h3>\n
Dairy and soy proteins<\/h3>\n
Flour proteins (gluten)<\/h3>\n