Fats and oils appear as creamy or fluid substances. The main difference between them is the melting point. When fat is heated it will melt and remain fairly firm at room temperature and become quite hard when chilled. Oils are fluid at room temperature. The oil when heated will change very little and becomes slightly thicker and cloudy in cold temperature.
The fats are used in baking and cooking to make the product soft increase palatability and are also known as shortening.
“Oil” normally refers to a fat with short or unsaturated fatty acid chains that is liquid at room temperature, while “fat” may specifically refer to fats that are solids at room temperature.
The scientific term “Lipid” comprises a group of substances which include natural fats and oils. Both those lipids consist of fatty acids and glycerol.
The only difference between fats and oils is that oils are liquid at room temperature (only exceptions are coconut and palm oil), whereas fats are solid as they contain saturated fatty acids. Saturation means the density of fat, in other words it is the molecular structure of the fat where the carbon atoms are bonded with hydrogen and oxygen.
The saturation is increased artificially by adding hydrogen into fat by a process known as saturation or hydrogenation of fat/oil. As example oil can be converted into margarine by passing hydrogen into it to make it saturated. This is done to stabilize the fats and oils and therefore the shell life of the product increases as it does not oxidize easily.
Those fats which are transformed artificially from oil to fats are known as trans-fats and they are not healthy ah they are the prime cause of cardiac disorder
FATS
Fats are divided into two categories:
- Animal fat.
- Vegetable fat compound.
Animal Fat
Animal fat include the following:
1. Butter
Butter is a dairy product made by churning fresh or fermented cream or milk. It is generally used as a spread and a condiment, as well as in cooking applications such as baking, sauce making, and frying. Butter consists of butterfat, water and milk proteins.
Most frequently made from cows‘ milk, butter can also be manufactured from the milk of other mammals including sheep, goats, buffalo, and Yaks
Butter contains 82% of fat, 14% of moisture, 2% proteins and 2% of minerals. The butter should be white in color. The manufacturer adds color for appearance. It should have a smooth, firm, plastic texture without trace of grain or oiliness. Butter has excellent creaming quality and when used for this purpose it should be soft but not oily. It is available in salted and unsalted varieties. If not stored properly the butter will get rancid.
2. Lard
Lard is pork fat and is a white solid fat. Its fat content is 99%. It provides low flavor to the products. It is neutral in color. It does not cream with sugar. It has a shortening power and has less creaming quality. It is good for making lardy cakes, flaky pastry and shallow frying.
3. Suet
Suet is found mostly around the kidney of beef or lamb. It is a hard white fat. The fat should be fresh, firm and dry with no unpleasant smell. To prepare suet break down the fat into small pieces and remove all skin and blood spots. Chop with a knife or grate with a fine grater. Keep the fat coated with some flour to prevent from sticking. This must be used cold and care must be taken when mixing with other ingredients. It is available in shredded or solid form. It is used for suet pastry, pudding and stuffing.
Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation
4. Ghee
Ghee is made by simmering unsalted butter in a large pot until all water has boiled off and protein has settled to the bottom. The cooked and clarified butter is then spooned off to avoid disturbing the milk solids on the bottom of the pan. Unlike butter, ghee can be stored for extended periods without refrigeration, provided it is kept in an airtight container to prevent oxidation and remains moisture-free. Texture, color, or taste of ghee depends on the source of the milk from which the butter was made and the extent of boiling.
It is the primary cooking medium of India and in many Arab countries.
Vegetable Fat
Following are the vegetable fat compounds:
1. Margarine
Margarine is the substitute of butter. It is made from hydrogenous of vegetable oil. T contains 85% of butter fat the ability to retain air during creaming operation. It lacks the flavor of butter and is used only for bakery purposes. It may be salted and unsalted and has higher melting point.
2. Pastry fat
Pastry fat is 100% fat. This is the toughest fat and is white in color. It has high melting point and can be used for puff pastry instead of butter. It has the ability to be rolled and manipulated to produce the buildup of layers in puff pastry. This special fat gives extra lift to the layers. Less fat is required to get the same effect. Pastry margarine performs better than butter in making puff pastry because of its high melting point. It does not melt quickly, thus allowing time for the puff pastry dough to rise sufficiently high while not making it heavy and soggy.
OILS
Edible oils are derived from fruit seeds and nuts. These oils have a limited purpose in pastry work as they do not have the ability to hold air. They are used mainly in mixtures where shortening and aeration are not essential. They are mainly used for deep and shallow frying and also for greasing of trays and moulds.
Cooking oil is plant, animal, or synthetic fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips, and in this sense might be more accurately termed edible oil.
Cooking oil is typically a liquid at room temperature, although some oils that contain saturated fat, such as coconut oil, palm oil and palm kernel oil are solid.
There is a wide variety of cooking oils from plant sources such as olive oil, palm oil, soybean oil, canola oil (rapeseed oil), corn oil, peanut oil and other vegetable oils, as well as animal-based fats like butter and lard.
Use of Fat and Oils
Fats and oils are the prime ingredients for cooking and baking around the world. Fats and oils give richness, variety of texture, and smoothness to the fat otherwise it may be too dry to eat. The melting and smoking points of fats and oils are very important to the chefs, as they decide the usage of the particular lipid in dish, one cannot use butter for deep frying as it has a very low smoking point, so it will burn to black till it reaches the temperature of frying.
Fats and oils are used for various purposes like:
Spreads – Butter and margarines are used for spreads and their function is to add the flavor, nutritional value and satiety value of breads.
Shortening – these are fats which shorten the gluten strand by surrounding them and make them more easily broken (short). When added to bread it gives a bit of tenderness, richness and sheen to the crumb.
Tempering – spices are added to hot oil/fat and then added to dal, curries, rice etc. to give better flavor, very common in Indian cuisine.
Salad dressings – fat is one of the main ingredients of salad dressings: like animal fat dressings like bacon fat, vinegar and seasonings, or other common dressings like vinaigrette, mayonnaise etc.
Flavored oil/infused oils – nowadays flavored oils play a very important role in food production, it can be used as salad dressings, garnishes or simply as accompaniments e.g. Chili oil, basil oil, peppers oil etc.
Frying medium – fats and oils are hugely used as cooking medium, i.e. pan roasting, deep frying, and sautéing. Fats with high smoking point is better for frying, the highest frying temperature needed for frying anything is 1990C/3900F.
Creaming and aerating effect – When making rich cakes, fat and sugar are beaten or creamed together. This process incorporates small air bubbles into the mixture and so lightens the product.
Role of shortenings
Fat provides nutrition and flavor.
Makes the product tender and palatable.
Helps retain air during creaming operation of fat , thus increases volume of the products.
Gives softness to the products.
Improves the taste and shelf life of the products.
Gives good flavor and color.
Provides extensibility in bread dough.
Improves the texture and grain in bread.
Is used for shortening value in various bakery products.
Increases eating quality of the products
Rendering of fat
Rendering is a process where the fat is melted on heat to separate the skin and non-fatty membrane. This is done over a low heat, and sometimes some water is added to it and brings to a boil, then the flame is reduced and let most of the water evaporates leaving behind the clear fat which can be strained and stored away.
Smoke Point of fats
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. 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.
Flash Point of fat
When a fat is heated to a high enough temperature, the vapors 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 .
Storage of fats
Fat becomes rancid having an unpleasant smell or odor due to the effect of heat, light and air. Fats and oils should be stored in a cool and dark place away from strong flavors as they absorb smell.
