Clarification and stabilization of wine Organic compounds used as fining agents are generally animal based, a possible cause of concern to vegans. The most common organic compounds used include egg whites, casein derived from milk, gelatin and isinglass obtained from the bladders of fish. Pulverized minerals and solid materials can also be used, with bentonite clay being one of the most common, thanks to its effectiveness in absorbing proteins and some bacteria. Activated carbon from charcoal is used to remove some phenols that contribute to browning as well as some particles that produce "off-odors" in the wine. In a process known as blue fining, potassium
Swim bladder duct, allowing the fish to fill up the swim bladder by "gulping" air. Excess gas can be removed in a similar manner. In more derived varieties of fish (the physoclisti) the connection to the digestive tract is lost. In early life stages, these fish must rise to the surface to fill up their swim bladders; in later stages, the pneumatic duct disappears, and the gas gland has to introduce gas (usually oxygen) to the bladder to increase its volume and thus increase buoyancy. In order to introduce gas into the bladder, the gas gland excretes lactic acid and produces carbon