FATS
Based on origin fats can be Animal fats or plant fats.
Based on degree of saturation there are three basic types of dietary fats
1. Monounsaturated fats (MUFAs),
2. Polyunsaturated fats (PUFAs) and
3. Saturated fats (SFAs)
The fat molecule is composed mostly of hydrogen atoms attached to carbon atoms in a carbon chain. On this molecule there are open spaces, like parking spaces. When all the available spots, or parking spaces, on the carbon atom are filled (i.e., saturated) with hydrogenated atoms, the fat is said to be saturated. If one or more places on the carbon are not filled with hydrogen, the fat is called unsaturated. A fat molecule with one empty space is called a monounsaturated fat and if two or more spots on the atom are empty, the fat is known as a poly unsaturated fat.
Saturated fatty acids are firmer at room temperature. Each carbon atom has two hydrogen atoms attached making them very stable and those with 16 or more carbon atoms have a high melting point.
Saturated fats are mainly the animal fats. They are found in meat, seafood (especially the shell fish such as lobsters, crabs, etc.), whole-milk and milk products (cheese, pander, and ice cream), and egg yolks. Some plant foods which are high in saturated fats are
Coconut, coconut oil and palm oil.
Trans - fatty acids are fats produced by heating liquid vegetable oils in the presence of hydrogen. This process is known as hydrogenation. The more hydrogenated an oil is, the harder it will be at room temperature.
Most of the Trans fats in our diets are found in commercially prepared baked foods like maw cakes and patties, margarines, vanaspati ghee (dalda), snack foods (farsaan, like french fries and onion rings, also contain a good deal of Tran’s fats. Trans fats are the worst for cholesterol levels because they raise bad LDL and lower good HDL. While you should limit your intake of saturated fats, it is important to completely eliminate Trans fats or partially hydrogenated oils from your diet.
Unsaturated fatty acids are fluid at room temperature. They have one hydrogen atom missing requiring the formation of a double bond. These are generally unstable as there are points in the molecule where addition of hydrogen /oxygen or other reactive substances can take place. This can cause rancidity and flavor reversion.
Unsaturated Fats - Polyunsaturated and Mono-unsaturated Unsaturated fats are found in products derived from plant sources, such as vegetable oils, nuts, and seeds.
There are two main types:-
A. Polyunsaturated fats (present in sunflower, corn, and soybean oils)
B. Monounsaturated fats (present in rice bran, canola, peanut, and olive oils).
Studies on intake of these fats have shown to decrease LDL levels and increase HDL levels, hence are labeled as good fat common examples of cooking fats include olive oil, lard, canola oil, walnut oil, butter, margarine and shortening....Fats are generally trimesters of glycerol and vegetable oils.
Margarine and vegetable shortening, which can be derived from the above oils, are used mainly for baking.
RANCIDITY
The development of any disagreeable odor and flavor in fats and oils or fatty phases of food is called Rancidity.
Rancidity is of two types-
A. Hydrolytic rancidity:- it is caused by lipases (substances that break down fats) which break down the fat into fatty acids and glycerol. The fatty acid are volatile at room temperature and cause off-flavor.
Example – rancidity in butter and products containing milk fats
Prevention- a) Heating- as it destroys lipases
b) Cooling – which retards the action of lipases
Oxidative rancidity/Autoxidation- initially fats take up oxygen at a very slow rate however after an induction phase rapid oxidation takes place resulting in off- flavors and odours.
Example- oils
Factors Effecting Autoxidisation
a) Traces of Metals like copper, nickel, iron catalyze rancidity by reducing induction period, increasing the rate of formation of free radicals (known as pro-oxidants as they encourage oxidation.)
b) Hematic compounds catalyze oxidative reactions even during the frozen state.
c) Light accelerates the development of rancidity. U-V rays and short wave light blues are most harmful as the cause photolysis (break down) of peroxide of free radicals.
Prevention – The addition of antioxidants prevents auto oxidation as they inhibit the chain reaction of oxidation.
Examples- Tocopherols - naturally present in vegetable e oils.
Butyrate hydroxyanisole (BHA)
Butyrate hydroxytoulene (BHT)
Propyl gal late
SMOKING OF FATS
High temperatures of frying can cause fats to undergo hydrolysis and polymerization of the fatty acids, releasing glycerol eventually. The glycerol molecule then loses water forming a very irritating aldehyde called ACROLEIN. The release of volatile fatty acids and caroling results in the smoking of fat. The temperature at which this occurs is known as the smoking point of fat or the SMOKE POINT.
FLAVOUR REVERSION
Flavor reversion is a special type of oxidative deterioration of edible fats.
It is characterized by the development of an objectionable flavor- before the onset of oxidative rancidity.
Factors effecting flavor reversion-
a) Metals like iron, copper
b) Presence of U-V rays
c) Heat
d) Oxygen
Flavor reversion is more prominent in some fats like-Soybean oil has a tendency to have ‘Beany’, ‘haylike’and eventually ‘fishy’ off flavors.
Prevention- the addition of sequester ants such as-
Ethylene dioxide tetra acetic acid (EDTA)
Processing of fats
REFINING
Oil can be extracted from oilseeds or extracted by dissolving in solvents. However these oils contain fat like substances such as phospholipids like lecithin (fat-protein complexes) to remove these they are wetted with water. The impurities become insoluble in
The oil and settle out. This process is known as DEGUMMING.
Further an alkali solution is added which settles additional impurities from the oil. These include free fatty acids – that combine with the alkali to form soaps which can be removed
By filtration or centrifugation. This treatment of oil with an alkali is known as REFINING
WINTERIZATION
Fats and oils are made up of a mixture of various triglycerides. The triglycerides containing more saturated fatty acids and long chain fatty acids tend to crystallize and settle out when the oil is chilled. Since crystallization must be avoided in fats such as salad oils,
They should be pre-treated by cooling and removing crystals before the product is bottled. The process of pre-treatment to remove crystals form the fat is known as WINTERIZATION
FRACTIONATION
Sometimes a solvent like acetone is used to dissolve the fat and then chilled to produce a crystalline fraction. The filtrate is recovered and chilled at lower temperature to get a second fraction and the process repeated again and again. This results in a purer
Recovery. Thus fractionation is an improvement on winterization.
HYDROGENATION
The addition of hydrogen to saturate fatty acid double bonds is HYDROGENATION. It is done to-
a) Change the viscosity of fat (hardening)
b) Increase the melting point of fat
c) Increase the shortening properties –as in margarine
Process of hydrogenation-
The de-aerated hot oil is whipped with hydrogen gas with a nickel catalyst in a closed vessel known as a converter, when the desired degree of hardening is reached the unreacted hydrogen gas is removed from the vessel by vacuum and the nickel catalyst is
Filtered out. However, hydrogenation changes the nutritional properties of some fats and some unsaturated fats lose essential fatty acids like linoleic acid making it less beneficial to health.
Based on origin fats can be Animal fats or plant fats.
Based on degree of saturation there are three basic types of dietary fats
1. Monounsaturated fats (MUFAs),
2. Polyunsaturated fats (PUFAs) and
3. Saturated fats (SFAs)
The fat molecule is composed mostly of hydrogen atoms attached to carbon atoms in a carbon chain. On this molecule there are open spaces, like parking spaces. When all the available spots, or parking spaces, on the carbon atom are filled (i.e., saturated) with hydrogenated atoms, the fat is said to be saturated. If one or more places on the carbon are not filled with hydrogen, the fat is called unsaturated. A fat molecule with one empty space is called a monounsaturated fat and if two or more spots on the atom are empty, the fat is known as a poly unsaturated fat.
Saturated fatty acids are firmer at room temperature. Each carbon atom has two hydrogen atoms attached making them very stable and those with 16 or more carbon atoms have a high melting point.
Saturated fats are mainly the animal fats. They are found in meat, seafood (especially the shell fish such as lobsters, crabs, etc.), whole-milk and milk products (cheese, pander, and ice cream), and egg yolks. Some plant foods which are high in saturated fats are
Coconut, coconut oil and palm oil.
Trans - fatty acids are fats produced by heating liquid vegetable oils in the presence of hydrogen. This process is known as hydrogenation. The more hydrogenated an oil is, the harder it will be at room temperature.
Most of the Trans fats in our diets are found in commercially prepared baked foods like maw cakes and patties, margarines, vanaspati ghee (dalda), snack foods (farsaan, like french fries and onion rings, also contain a good deal of Tran’s fats. Trans fats are the worst for cholesterol levels because they raise bad LDL and lower good HDL. While you should limit your intake of saturated fats, it is important to completely eliminate Trans fats or partially hydrogenated oils from your diet.
Unsaturated fatty acids are fluid at room temperature. They have one hydrogen atom missing requiring the formation of a double bond. These are generally unstable as there are points in the molecule where addition of hydrogen /oxygen or other reactive substances can take place. This can cause rancidity and flavor reversion.
Unsaturated Fats - Polyunsaturated and Mono-unsaturated Unsaturated fats are found in products derived from plant sources, such as vegetable oils, nuts, and seeds.
There are two main types:-
A. Polyunsaturated fats (present in sunflower, corn, and soybean oils)
B. Monounsaturated fats (present in rice bran, canola, peanut, and olive oils).
Studies on intake of these fats have shown to decrease LDL levels and increase HDL levels, hence are labeled as good fat common examples of cooking fats include olive oil, lard, canola oil, walnut oil, butter, margarine and shortening....Fats are generally trimesters of glycerol and vegetable oils.
Margarine and vegetable shortening, which can be derived from the above oils, are used mainly for baking.
RANCIDITY
The development of any disagreeable odor and flavor in fats and oils or fatty phases of food is called Rancidity.
Rancidity is of two types-
A. Hydrolytic rancidity:- it is caused by lipases (substances that break down fats) which break down the fat into fatty acids and glycerol. The fatty acid are volatile at room temperature and cause off-flavor.
Example – rancidity in butter and products containing milk fats
Prevention- a) Heating- as it destroys lipases
b) Cooling – which retards the action of lipases
Oxidative rancidity/Autoxidation- initially fats take up oxygen at a very slow rate however after an induction phase rapid oxidation takes place resulting in off- flavors and odours.
Example- oils
Factors Effecting Autoxidisation
a) Traces of Metals like copper, nickel, iron catalyze rancidity by reducing induction period, increasing the rate of formation of free radicals (known as pro-oxidants as they encourage oxidation.)
b) Hematic compounds catalyze oxidative reactions even during the frozen state.
c) Light accelerates the development of rancidity. U-V rays and short wave light blues are most harmful as the cause photolysis (break down) of peroxide of free radicals.
Prevention – The addition of antioxidants prevents auto oxidation as they inhibit the chain reaction of oxidation.
Examples- Tocopherols - naturally present in vegetable e oils.
Butyrate hydroxyanisole (BHA)
Butyrate hydroxytoulene (BHT)
Propyl gal late
SMOKING OF FATS
High temperatures of frying can cause fats to undergo hydrolysis and polymerization of the fatty acids, releasing glycerol eventually. The glycerol molecule then loses water forming a very irritating aldehyde called ACROLEIN. The release of volatile fatty acids and caroling results in the smoking of fat. The temperature at which this occurs is known as the smoking point of fat or the SMOKE POINT.
FLAVOUR REVERSION
Flavor reversion is a special type of oxidative deterioration of edible fats.
It is characterized by the development of an objectionable flavor- before the onset of oxidative rancidity.
Factors effecting flavor reversion-
a) Metals like iron, copper
b) Presence of U-V rays
c) Heat
d) Oxygen
Flavor reversion is more prominent in some fats like-Soybean oil has a tendency to have ‘Beany’, ‘haylike’and eventually ‘fishy’ off flavors.
Prevention- the addition of sequester ants such as-
Ethylene dioxide tetra acetic acid (EDTA)
Processing of fats
REFINING
Oil can be extracted from oilseeds or extracted by dissolving in solvents. However these oils contain fat like substances such as phospholipids like lecithin (fat-protein complexes) to remove these they are wetted with water. The impurities become insoluble in
The oil and settle out. This process is known as DEGUMMING.
Further an alkali solution is added which settles additional impurities from the oil. These include free fatty acids – that combine with the alkali to form soaps which can be removed
By filtration or centrifugation. This treatment of oil with an alkali is known as REFINING
WINTERIZATION
Fats and oils are made up of a mixture of various triglycerides. The triglycerides containing more saturated fatty acids and long chain fatty acids tend to crystallize and settle out when the oil is chilled. Since crystallization must be avoided in fats such as salad oils,
They should be pre-treated by cooling and removing crystals before the product is bottled. The process of pre-treatment to remove crystals form the fat is known as WINTERIZATION
FRACTIONATION
Sometimes a solvent like acetone is used to dissolve the fat and then chilled to produce a crystalline fraction. The filtrate is recovered and chilled at lower temperature to get a second fraction and the process repeated again and again. This results in a purer
Recovery. Thus fractionation is an improvement on winterization.
HYDROGENATION
The addition of hydrogen to saturate fatty acid double bonds is HYDROGENATION. It is done to-
a) Change the viscosity of fat (hardening)
b) Increase the melting point of fat
c) Increase the shortening properties –as in margarine
Process of hydrogenation-
The de-aerated hot oil is whipped with hydrogen gas with a nickel catalyst in a closed vessel known as a converter, when the desired degree of hardening is reached the unreacted hydrogen gas is removed from the vessel by vacuum and the nickel catalyst is
Filtered out. However, hydrogenation changes the nutritional properties of some fats and some unsaturated fats lose essential fatty acids like linoleic acid making it less beneficial to health.
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