What is oxidative rancidity?
Oxidative rancidity in foods refers to the perception of objectionable flavours and odours caused by oxidation of the unsaturated fatty acid chains of lipids by atmospheric oxygen. Because of the ‘spontaneous’ nature of the reaction the process is frequently referred to as autoxidation.
What is oxidative rancidity caused by?
Oxidative rancidity is a chemical reaction catalyzed by heat, ultraviolet light, heavy metals and oxygen. Many of these factors are obviously present during the extrusion process. Oxidative rancidity is best controlled by the addition of antioxidants and ‘oxygen scavengers’.
What is the main purpose of huble’s test?
(e) Huble’s Test: This test is used to know the degree of unsaturation in the given sample. Oils on reaction with Huble’s reagent fads the violet colour of iodine then it is unsaturated and if the colour persists then the given fat or oil is saturated.
How does linseed oil oxidize?
Linseed oil oxidation, which incorporates cross-linking reaction, involves oxygen consumption and induces increasing sample mass. Thus, the mass reading of a TGA instrument corresponds to a combined effect of mass-gaining (i.e., oxygen consumption) and mass-losing (i.e., emission of carbon oxides and water) reactions.
What are the products of oxidative rancidity?
Oxidative rancidity is a reaction of fatty acids with oxygen. More specifically it is the reaction of double bonds in unsaturated fatty acids with oxygen. Upon reacting with oxygen very reactive components (among others hydroperoxides) will be formed.
How can oxidative rancidity be prevented?
Oxidative rancidity can be prevented by light-proof packaging, oxygen-free atmosphere (air-tight containers) and by the addition of antioxidants.
What is in huble’s reagent?
Huble’s reagent: (a mixture of 7% mercury chloride in alcohol and 5% iodine in 96% alcohol is added in equal proportion).
What is the significance of huble’s test what does it mean when the violet color does not fade away?
Huble’s test Huble’s reagent reacts with alcoholic solution of iodine that contains some mercuric chloride. During the reaction, the violet colour of iodine fades away if the oil or fat is unsaturated. If the oil or fat is saturated, the violet colour of iodine does not fade away.
Is linseed same as flaxseed?
Also known as flaxseed, linseed are small seeds that can be eaten whole, ground or pressed to make oil.
Is linseed oil toxic to animals?
Linseed oil is non-toxic to sheep or horses. In fact, it is sometimes used in sheep and cattle rations as a source of energy and Omega 3 fatty acids. Raw linseed oil has a slower drying time than boiled linseed oil but does not contain synthetic solvents.
Oxidative rancidity, one of the major causes of quality deterioration in foods, is caused by the oxidative deterioration of lipids by atmospheric oxygen.
What causes oxidative rancidity in macadamias?
Oxidation leads to oxidative rancidity and is the result of oxygen attacking glycerides. Oxidation can be initiated by heat, pro-oxidants, certain enzymes (lipoxygenases) or light ( Robards et al., 1988 ). Macadamias are usually tested for oxidative rancidity by the Peroxide Value (PV) method (AOAC method 965.33).
How to prevent oxidative rancidity during storage of food products?
Light is another essential factor that should be excluded to prevent oxidative rancidity during storage of foods. For oils, consumer preferences for clear containers preclude the use of opaque materials. Inactivation of metal catalysts by using chelating agents is another effective control method against lipid oxidation.
What is Hydrolytic rancidity?
Hydrolytic rancidity is the development of an unpleasant odor upon the hydrolysis of triglycerides, releasing their free fatty acids. This is a chemical reaction where the lipid usually reacts with water.