(A) MELTING-POINT:

 Fats melt when heated. Since fats are mixtures of TRIGLYCERIDES they do not have a distinct melting-point but melt over a range of temperature. The temperature at which melting starts is called the slip point. Most fats melt at a temperature between 30°C and 40°C. The melting-point for oils is below normal air temperature. The more double bonds the lower the melting point.

(B) SMOKE-POINT:

When a fat or oil is heated to a certain temperature it starts to decompose, producing a blue haze or smoke and a characteristic acrid smell. Most fats and oils start to smoke at a temperature around 200°C. In general, vegetable oils have a higher smoke-point than animal fats. Decomposition of the triglycerides produces small quantities of glycerol and FATTY acids. The glycerol decomposes further producing a compound called acrolein. This decomposition is irreversible and, when using a fat or oil for DEEP frying, the frying temperature should be KEPT below the smoke-point. Smoke-point is a useful measure when assessing the suitability of a fat or oil for frying purposes. Repeated heating of a fat or oil or the presence of burnt food particles will reduce the smoke-point. Repeated beating will also produce oxidative and hydrolytic changes in the fat and result in the accumulation of substances GIVING undesirable flavours to the foods cooked in the fat.

( C ) FLASH-POINT :

When a fat is heated to a high enough temperature, the vapours given off will spontaneously ignite. This temperature is known as the flash-point. For corn oil the flash-point is 360°C. A fat fire should never be put out with water; this will only spread the fire. The heat should be turned off and the oxygen supply cut off by covering the container of burning fat with a lid or blanket.

(A) MELTING-POINT:

 Fats melt when heated. Since fats are mixtures of triglycerides they do not have a distinct melting-point but melt over a range of temperature. The temperature at which melting starts is called the slip point. Most fats melt at a temperature between 30°C and 40°C. The melting-point for oils is below normal air temperature. The more double bonds the lower the melting point.

(B) SMOKE-POINT:

When a fat or oil is heated to a certain temperature it starts to decompose, producing a blue haze or smoke and a characteristic acrid smell. Most fats and oils start to smoke at a temperature around 200°C. In general, vegetable oils have a higher smoke-point than animal fats. Decomposition of the triglycerides produces small quantities of glycerol and fatty acids. The glycerol decomposes further producing a compound called acrolein. This decomposition is irreversible and, when using a fat or oil for deep frying, the frying temperature should be kept below the smoke-point. Smoke-point is a useful measure when assessing the suitability of a fat or oil for frying purposes. Repeated heating of a fat or oil or the presence of burnt food particles will reduce the smoke-point. Repeated beating will also produce oxidative and hydrolytic changes in the fat and result in the accumulation of substances giving undesirable flavours to the foods cooked in the fat.

( C ) FLASH-POINT :

When a fat is heated to a high enough temperature, the vapours given off will spontaneously ignite. This temperature is known as the flash-point. For corn oil the flash-point is 360°C. A fat fire should never be put out with water; this will only spread the fire. The heat should be turned off and the oxygen supply cut off by covering the container of burning fat with a lid or blanket.