Author: Robert Joseph Manning

Publisher:

Published: 1948

Total Pages: 78

ISBN-13:

Rancidity in fats and oils is primarily due to oxidation of unsaturated fatty acid chains. Oxygen absorbed from the atmosphere forms a peroxide by addition to a douple bond. Subsequent oxidation breaks the carbon chain and forms shorter chain acids and aldehydes which cause the fat to have an unpleasant odor and taste. This oxidative rancidity can be delayed by the addition of anti-oxidants to the fat. The most effective anti-oxidants have been found to be phenolic compounds. The effect of these substances can be greatly enhanced by the addition of very small amounts of certain organic and mineral acids called synergists. Verious substances were tested for their anti-oxygenic activity in chicken fat. A high quality sample of pooled chicken leaf fat was used as the substrate in this study. The procedure used was that of King, Roschen and Irwin of Swift and Company. It involves aeration of the fat sample at an elevated temperature. The degree of rancidity was determined by iodimetric analysis for peroxides at regular intervals. The relative value of the various anti-oxidants used is shown in Table I. [The effect of an anti-oxidant and a synergist is shown graphically in Figure I.] A combination of nordihydroguaiaretic acid with citric or phosphoric acid was found to be the most effective stabilizer for chicken fat among the substances tested. Gallic acid and gum guaiac also gave excellent results as anti-oxidants. An easy method of determining the point of rancidity in chicken fat was found. In every experiment, bleaching of the bright yellow color of the fat coincided with the onset of rancidity.