Rendering is the process of extraction of fat from animal tissue by application of heat. Rendering is also called trying. During rendering fat cells are ruptured, expelled and water evaporated. The accompanying connective tissues are separated as solid residue called cracklings. Rendering can be done by following two methods;
- Wet rendering
- Dry rendering
dry rendering involves cooking of meat scraps under vacuum in steam jacketed kettles. The heat is transferred indirectly by conduction. The heat and pressure gradients that develop inside the vessel cause fat to leach out. These also lead to denaturation of protein and removal of water. The fat is finally freed from residual water by evaporation and proceed further for purification.
Use of lard: these are used as Shortening in bakery. It is also used as raw material for margarine preparation and is principle source of fat used in sausage.
Use of tallow: it is Inedible but have Industrial use such as boot polish, glue, cosmetics and grease etc.
Shortening; these compounds break the network of gluten in food so that bite is shortened, i.e. easy bite. Example; ghee, butter, fat etc.
Extraction of oil from oil bearing fruits:
Hot water extraction method is used for obtaining oil from fruits like coconut, palm, avocado by application of hot water.