Oils and fats form an essential part of the modern diet and have been used for the preparation of food since time immemorial. These are rich source of dietary energy and contain more than twice the calorific value equivalent to the amount of carbohydrates. Functionality of oils and fats not only adds flavor in the food, but it also increases the nutritional value of food also. They serve as a heat transfer medium at elevated temperatures (e.g., frying), improve taste sensation (spreads and salad dressings), give texture and flavor to a wide range of foodstuffs, supply a concentrated source of energy, deliver critical building elements for the body and act as a carrier for essential minor components like vitamins A and D.
Fats and oils are constructed of building blocks called “triglycerides” resulting from the combination of one unit of glycerol and three units of fatty acids. They are insoluble in water but soluble in most organic solvents. They have lower densities than water, and may have consistencies at ambient temperature of solid, semisolid, or clear liquid. When they are solid appearing at normal room temperature, they are referred to as “fats,” and when they are liquid at that temperature, they are called “oils.” Fats and oils are classified as “lipids” which is a category that embraces a broad variety of chemical substances. In addition to triglycerides, it also includes mono- and diglycerides, phosphatides, cerebroids, sterols, terpenes, fatty alcohols, fatty acids, fat-soluble vitamins, and other substances.
Classification of Edible Oil- Source of Raw Material
Based on the source of raw materials, edible oil can be classified into three groups:
- Animal Oil: It refers to the oil obtained from animals, such as beef oil, pig, fish, etc.
- Vegetable Oil: It refers to oils extracted /processed from plant roots, stems, leaves, fruits, flowers, or seeds tissue. Example includes soybean oil, rapeseed oil, cottonseed oil, peanut oil, sesame oil, rice bran oil, sunflower oil, corn oil, tea seed oil, flax seed oil, safflower seed oil, etc.
- Microbial Oil: Single-cell lipids, refer to edible fats extracted and processed from certain microorganisms, including yeast, fungi, and algae.
Classification of Edible oil- Type of Processing Method Used
Based on type of processing the edible oil receives, it can be classified into following categories:
- Hot Pressed Oil: These oils are extracted by pressing them at high temperatures due to which acidity of oil increases significantly and it loses most of its natural quality. These oils require refinement for making them fit for human consumption.
- Cold Pressed Oil: Unlike hot pressed oils, extraction process for these oils takes place at room temperature, at around 27 degrees centigrade due to which acid value is relatively low. These oil products can be directly consumed after precipitation and filtration and thus do not require any chemical refinement process.
- Leached Oil: When oil is extracted from the crushed mass of plant/animal biomass with the help of solvent, then this kind of oil is known as Leached oil. The leaching process depends mainly on the chemical structure of the solvent and the kind of solute that will be extracted from solid material. This probably follows the principle ‘like dissolves like’.
- Refined oil: Edible oils purchased in stores are known as “RBD” oils. These are oils that have been Refined, Bleached and Deodorized. Each of these steps is used to create a final oil that is consistent in taste, color and stability. As a result, these oils are generally tasteless, odorless, and colorless regardless of the original oilseed type or quality.
- Hydrogenated Oil: Generally, most of the oils are typically liquid at room temperature, therefore many companies use hydrogenation to get a more solid and spreadable consistency. During this process, hydrogen molecules are added to alter the texture, stability, and shelf life of the final product. Hydrogenated oils are also used in many baked goods to improve taste and texture.
- Blended Oil: Blended edible oil means an admixture of any two edible oils where the proportion by weight of any edible oil used in the admixture is not less than 20 percent. The blended mixture shall be clear, free from rancidity, suspended or insoluble matter or any other foreign matter, separated water, added coloring matter, flavoring substances, mineral oil, or any other animal and non-edible oils, or fats, argemone oils, hydrocyanic acid, castor oil and tricresyl phosphate.
Fat is an important part of our food as it serves many important physiological functions such as meeting energy requirements, being structural component of cells, starting component of various inflammatory mediators, energy reserve and provides insulation against freezing temperatures in newborn. As it plays an important part in our food and nutrition, its quality and quantity bear a huge impact on overall health. Therefore, oil manufacturers must pay special attention for processing oil that is non-hazardous to the health of the consumers.