Question

Chemistry of lipid oxidation?

–State specific aspects (aromas, colors) that play into this

Answer 1

Lipids are heterogeneous compounds , components of living organisms, insoluble in water but soluble in nonpolar solvents such as hydrocarbons. Lipids include oils or fats of our diet and phospholipids. Unlike proteins and carbohydrates they donot contribute structural strength but rather act as a depot storage forms of energy metabolites in adipose tissue. They are primarily a source of fuel for living organisms. Lipids in foods contribute to food quality by providing organoleptic character notes that make particular foods desirable. These properties include flavor, aroma, color, texture and mouthfeel. When oxidized lipids lead to primary and secondary products that can affect adversely these functions.

Thus lipid oxidation is the oxidative deterioration of lipids containing any number of carbon-carbon double bonds such as fatty acids and cholesterol .

Lipid oxidation produces various primary and secondary by-products that influence food quality. It is the major cause of quality deterioration, developed rancidity in raw or fatty tissues ,produces WOF in cooked meats ,oxidized the flavors in oils, loss of functional properties ,loss of nutritional values, formation of toxic compounds ,Forms colored products, Many secondary by-products of lipid oxidation are potential carcinogens .

The overall mechanism of lipid oxidation consists of three phases:

(1) initiation, the formation of free radicals;

(2) propagation, the free-radical chain reactions; and

(3) termination, the formation of nonradical products.

Thus in detail

Initiation

RH + (reactive oxygen species) ·OH -->R· + H₂O

Propagation

R· + O₂ ------> ROO·

ROO· + RH ------> R· + ROOH

ROOH -------> RO· + HO^-

Termination

R· + R· ------> RR

R· + ROO· ------> ROOR

ROO· + ROO· ------> ROOR + O₂