CHAPTER IV Chemical properties of fats and fatty acids Reaction: Esterification Saponification Hydrolysis (De)Hydrogenation Alkoxylation Pyrolysis Halogenation Addition

Physical properties of fat and oils: Freshly prepared fats and oils are colorless, odorless and tasteless.Any color, or taste is due to association with other foreign substances, e.g., the yellow color of body fat or milk fat is due to carotene pigments(cow milk). Fats have specific gravity less than 1 and, therefore, they float on water. Fats are insoluble in water, but soluble in organic solvents as ether and benzene. Melting points of fats are usually low, but higher than the solidification point,

Esterification In chemistry, esters are chemical compounds derived from an acid (organic or inorganic) in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group. Usually, esters are derived from a carboxylic acid and an alcohol.

Saponification Alkaline hydrolysis produces glycerol and salts of fatty acids (soaps). Soaps cause emulsification of oily material this help easy washing of the fatty materials.

Hydrolysis They are hydrolyzed into their constituents (fatty acids and glycerol) by the action of super heated steam, acid, alkali or enzyme (e.g., lipase of pancreas). During their enzymatic and acid hydrolysis glycerol and free fatty acids are produced.

Most of fatty acids have unbrached chains and they have an even number of carbon atoms. The double bonds in unsaturated fatty acids are all cis and not conjugated. Many naturally occurring fatty acids contain two or three double bonds. Triple bond rarely occur in fatty acids. Saturated fatty acids have relatively high points and unsaturated fatty acids have relatively low points.

(De)Hydrogenation Hydrogenation or hardening of oils: It is a type of addition reactions accepting hydrogen at the double bonds of unsaturated fatty acids. The hydrogenation is done under high pressure of hydrogen and is catalyzed by finely divided nickel or copper and heat. It is the base of hardening of oils (margarine manufacturing), e.g., change of oleic acid of fats (liquid) into stearic acid (solid). It is advisable not to saturate all double bonds; otherwise margarine produced will be very hard, of very low biological value and difficult to digest.

Advantages for hydrogenated oil or fat are as follows: It is more pleasant as cooking fat. It is digestible and utilizable as normal animal fats and oils. It is less liable to cause gastric or intestinal irritation. It is easily stored and transported and less liable to rancidity. Disadvantages of hydrogenated: fats include lack of fat-soluble vitamins (A, D, E and K) and essential fatty acids

Solid commercial cooking fats are manufactured by partial hydrogenation of vegetable oils. Completed hydrogenation of the oil is very hard and brittle. One commercial advantage of partial hydrogenation is to give the fat a longer shelf-life.

Alkoxylation (Ethoxylation) Alkoxylates are the hydrocarbons manufactured by alkoxylation process in which alkylene Oxide such as ethylene oxide ( 1, 2 Epoxethane), Propylene Oxide ( 1, 2 Epoxpropane) is added in blockwise or randomly to some hydrophobe like phenols, alcohols ,fatty acids , amines etc. ethylene oxide

Pyrolysis Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). It involves the simultaneous change of chemical composition and physical phase, and is irreversible. Plant oil asphalt (POA) is the residue biomass generated in biodiesel and fatty acids (FAs) industry. POA is a mixture of polymeric products of FAMEs and some natural components like waxes origin from plant oils. Non-catalytic vacuum pyrolysis of POA could obtain 71 wt% of pyrolytic oil.

Halogenation Neutral fats containing unsaturated fatty acids have the ability of adding halogens (e.g., hydrogen or hydrogenation and iodine or iodination) at the double bonds. - It is a very important property to determine the degree of unsaturation of the fat or oil that determines its biological value

Addition S, Cresols and merkaptans

Sulfur

Allicin is an organosulfur compound obtained from garlic, a species in the family Alliaceae. It exhibits antibacterial, antifungal, antiviral, and antiprotozoal activity. Allicin is garlic's defense mechanism against attacks by pests.

Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant. Thiols are often referred to as mercaptans. Benzyl mercaptan

Cresols (also hydroxytoluene) are organic compounds which are methylphenols. They are a widely occurring natural and manufactured group of aromatic organic compounds, which are categorized as phenols (sometimes called phenolics)