This is a process whereby pigments, impurities, trace metals; gums and oxidized materials are removed from oils and fats by absorptive cleansing using bleaching clays or activated carbon. Bleaching of edible oils or fats is generally carried out under vacuum at 70 ºC to 120 ºC.

Single or straight oils and fats are often unable to satisfy the complex technical specifications prescribed for a particular product application. Only by blending, i.e. mixing two or more straight or modified oils and fats, can the correct balance of properties such as melting point, plastic range, color, texture, iodine value, etc. be obtained.

Natural constituents that give crude palm oil its bright orange-red color and which are completely destroyed during refining. Carotenes can also be partially destroyed by oxidation under adverse conditions during production, storage and transport of crude palm oil. However, upon request, palm oil can be specially processed to maintain the carotenes.

Substances having different densities will separate by gravity. For instance, oil is lighter than water and easily forms a separate upper layer. The effect of gravity can be accentuated by centrifugation, i.e. by rotating the mixture to be separated in a container. Centrifugation is often used in oil mills and refineries to separate impurities and water from oils and fats and also fat crystals from a fat slurry after addition of a surface-active agent.

This refers particularly to the removal of free fatty acids by alkali. The alkalis used are usually sodium hydroxide (caustic soda) or soda ash, either singly or in combination. One novel chemical refining technique uses aqueous ammonia as the alkali.

This is a test to determine the temperature at which oil begins to cloud as a result of crystallization under controlled cooling. The cloud point is related to the instauration of an oil. In general, the higher the instauration of an oil, the lower its cloud point will be.

This fat has a unique chemical composition, consisting mainly of the triglycerides POS (palmito-oleo-stearin), POP (palmito-oleo-palmitin) and SOS (stearo-oleo-stearin). lt is hard and brittle at room temperature but melts very sharply below body temperature. It therefore gives chocolate its desirable properties of 'snap' and 'melt-in-the-mouth', and is highly valued.

These are fats designed to have a glyceride composition similar to that of cocoa butter. Their properties are similar and they are compatible with cocoa butter in mixtures for chocolate manufacture.

These are fats usually based on laurics, i.e. on palm kernel oil or coconut oil. They have snap and melting properties similar to cocoa butter but a different chemical composition. They are not compatible with cocoa butter and the presence of more than 20% cocoa butter in a mixture with them leads to softening and / or bloom formation.

Crystallization is the three-step process of forming crystals and may take place from a melt or from a solution. The three steps are super cooling or super saturation; formation of crystalline nuelei; and growth of crystals. The process is important for fats in order to produce the desired texture in a solid product, or as a preliminary to fractionation.

This process involves removal of those trace components, present in all edible oils, which give rise to odors and flavors. It is accomplished by the application of heat, steam and vacuum.

The Triglyceride molecules that make up oils and fats are each composed of three molecules of fatty acids and one molecule of glycerol. The fatty acid composition of a fat or oil is expressed as the percentage of each of the various fatty acids present in the mixture.

Fractionation is the process of separation of an oil or fat into two or more fractions. The oil is cooled and crystallized under controlled conditions and the solid separated from the liquid by filtration or centrifugation. Fractionation of a fat is made possible by solubility differences between the component triglycerides. The fractions obtained have different physical and chemical properties from the original oil, and have wide applications.

This process involves addition of hydrogen to the double bonds of unsaturated acids in the molecules of an oil. By doing this, the properties of the fatty acids are changed and therefore also the properties and physical behavior of the oil. This chemical reaction is carried out by reacting the oil with gaseous hydrogen at elevated temperature and pressure, in the presence of a catalyst, usually nickel. Hydrogenation of oils and fats is also known as hardening.

The fatty acids of palm oil can be rearranged in relation to their position on the triglyceride molecules. The rearrangement, which occurs in a random manner, is conducted in the presence of a catalyst, and is termed interesterification. The rearrangement brings about a change in the physical properties of the oil, which may leave the products more useful for making margarine, vanaspati and shortening.

This is the most widely distributed of all fatty acids, found in practically every vegetable and animal fat. Rich sources are olive and peanut oils and palm olein. Oleic acid contains 18 carbon atoms and one double bond in the cis configuration. Palm oil contains about 40% oleic acid.

When oils or fats are oxidized, the unsaturated fatty acids react, resulting in rancidity. The most common mechanism of oxidation is a free radical chain reaction. This process is retarded by antioxidants such as tocopherols and tocotrienols, and accelerated by prooxidants such as trace metals and heat. The primary products of oxidation are hydro peroxides. These then decompose into secondary oxidation products such as aldehyes and ketones.

Palm olein is the liquid, more unsaturated fraction separated from palm oil after crystallization at a controlled temperature. The olein consists of a more homogeneous mixture of triglycerides and has properties and uses which are different from those of the original oil.

This is the oil obtained from the kernel of the oil palm fruit. Its chemical composition is quite different from that of palm oil, which is obtained from the flesh of the palm fruit. Palm kernel oil is a lauric type, similar to coconut oil.

Palm stearin is the more saturated and more solid fraction of palm oil. Its fatty acid composition is variable depending on the process employed to isolate it, ranging from 53% to 88% for saturates, 16% to 37% for monounsaturated, and 3% to 10% for polyunsaturated. Palm stearin is used in formulating products that require a higher degree of saturation, such as margarines and shortenings.

Physical refining may be defined as the removal of free fatty acid from an oil by the action of high temperature, high vacuum and live steam. lt is also referred to as steam refining. This process is normally carried out in a single step with deodorization.

These are fatty acids having two or more double bonds in their carbon chain. The most common polyunsaturated fatty acid is linoleic acid. Corn oil, sunflower oil and soybean oil are some vegetable oils that are rich in PUFA.

All crude oils and fats when freshly produced contain unwanted impurities. These consist essentially of free fatty acids, gums, trace metals, odoriferous materials and water. The various processes used to remove all these entities are normally known collectively as 'refining'.

Fats consist of a complex mixture of glycerides and therefore do not have sharp melting points, unlike pure chemical substances. The slip melting point of a fat is defined as the temperature at which a column of fat in an open capillary tube moves up the tube when it is subjected to controlled heating in a water bath. Because of their polymorphic behavior, the slip point of some fats is dependent on the previous treatment of the sample.

Fat splitting is usually carried out with steam at high temperature and pressure (e.g. 260 'C and 55 bar) to give glycerol and a mixture of fatty acids. This process opens the gateway to the oleochemical field.

In the chemical refining of crude oils, the free fatty acids are removed by neutralization with alkali and settle to the bottom as alkali soaps, known as soap stock.

Chemically, stearic acid is an 18-carbon saturated fatty acid. Commercially, the term is used for mixed solid acids of various compositions. Stearic acid is used for industrial purposes in the rubber and oleochemical industries.

Trans fatty acids are formed during the partial hydrogenation of an oil. Some of the unsaturated fatty acids present are changed from their natural, bent cis shape to a straight trans shape like that of the saturated acids. In consequence, many of the physical properties of trans-acids, such as melting point, are nearer to those of the saturated acids, although double bonds are still present.