Rancidity Research Articles

Oxidative Rancidity of Fat and Oil (V)

Oxidative Rancidity of Fat and Oil (V)

Rancidity of Butter Fat

Butter is the substance containing practically the whole of the fat of the milk from which it is prepared, produced by the continual shaking or beating of cream or of the milk itself. When butter is freshly produced it consists of a nodular mass which is then worked in order to remove excess of water and make the whole a visibly homogeneous mass. With a view to find out the agencies responsible for increasing the rancidity of butter fat an experiment was conducted in the State Ghee Grading Laboratory, Madras.

Studies on the Evaluation of the Degree of Rancidity of Fats and Fatty Foods

The relation of chemical methods to an organoleptic method using various edible oils which were oxidized by the active oxygen method, was investigated. As the results, it was revealed that total and steam distilled carbonyl values which were calculated as saturated carbonyl and monoenal are the most recommendable indicators for the rancidity of the oil followed by peroxide value, while TBA and acid values are not suitable as the indicators.

Studies on Rancidity of Fats in Foods (II)

In this paper the authors investigated the composition of fatty acids in fats extracted from the pre-cooked Chinese noodles preserved as the same way in the previous report, and the fractionation of the fats by column-chromatography on Florisil, and then, the toxicity test on the fractionated fats to mice.After the separation of the extracted fats into the two fractions of the esterified and the free fatty acids, the composition ratio of fatty acids in each fraction was calculated by gas-chromatography with FID, respectively.In the fraction of the esterified fatty acids the ratio of the unsaturated fatty acids decreased remarkably in the sample preserved for 7 weeks, on the other hand, in the fraction of the free fatty acids, it did so in the sample preserved for 6 weeks. In the both fractions linoleic acid decreased most greatly, and oleic acid secondly.An unknown peak was found just in front of the peak of stearic acid on gas-chro-matogram of the free fatty acid fraction in the sample preserved for 5 weeks and more longer, and its retention time was identical with that of 8-formyloctanoic acid which was the product derived from methyl linoleate by auto-oxidation.From the result of the toxicity test by oral administration to mice on the samples obtained by fractionation of the fats incubated for 14 weeks which were most toxic to mice (mortality, 100%) in the previous report, it was found that the mixed fraction of monoglyceride and free fatty acids was most toxic (mortality, 70%).

Studies on Rancidity of Fats in Foods (I)

The powder of the commercial pre-cooked Chinese noodles was preserved in an incubator at 50°C to make fats rancid, and then, the fats were extracted every week from the powder by the method of Folch, et al. Using those fats the authors investigated the relationship between the degree of rancidity of the fats and the acute toxicity to mice.It was shown generally that the five indices which indicate the degree of rancidity of fats changed remarkably in the samples during preservation for 6 to 8 weeks. Iodine value decreased remarkably after 6 weeks, on the other hand, acid value increased markedly at the same time. Peroxide value (POV) had its maximum after 6 weeks, and decreased markedly after 8 weeks and later. Carbonyl value raised sharply after 6 weeks, and remained almost unchanged later. TBA value raised sharply after 6 or 7 weeks, when it had its maximum, and fell down later.From the data of thin-layer chromatography and infrared spectra of the rancid samples, it was shown that as the rancidity progressed triglyceride in those samples decreased, diglyceride increased conversely, and monoglyceride and free fatty acids came to be detected after 5 weeks.Although it had been described by another authors that the toxicity of the rancid fats was parallel to those POV, from the result of our toxicity test to mice (30ml/kg, a single oral administration) it was found that the toxicity was very low in the sample having high POV preserved for 7 weeks (mortality, 20%), was very high in the two samples having lower POV preserved for 8 weeks and having more lower POV preserved for 14 weeks (mortality, both 100%).Therefore. it is considered that the toxicity of the rancid fats is not always caused by fatty peroxide, but is much ascribed to more oxidized products.

Studies on Oxidative Rancidity of Fat and Oil (IV)

Methyl linoleate hydroperoxide (ML-HPO) was separated from methyl linoleate autoxidized at about 10°C by the combination method of simple countercurrent extraction and column chromatography. The peroxide value of ML-HPO was more than 5, 780meq/kg. This value indicated that the material was essential pure monoperoxide. ML-HPO had a conjugated diene and a hydroperoxide group. Being hydrogenated with platinum oxide, ML-HPO absorbed 3.11 mole of hydrogen, and was converted into a mixture of great quantity of hydroxystearic acid methyl esters and slight unknown material. The methyl esters contained equal amount of 9 and 13 hydroxystearic acid methyl esters.When ML-HPO stored in air and in nitrogen at 25°C, the contents of conjugated diene and peroxide value of ML-HPO decreased respectively. This fact evidences that decomposition of ML-HPO occurred in those atmospheric conditions. Methyl 8-formyloctanoate (MFO) was detected in oxidized ML-HPO, was not detected in the substance that decomposed under nitrogen, by gasliquid chromatographic analysis.ML-HPO and hydroxyoctadecadienoic acid methyl ester (HODE) which was obtained from reduction of ML-HPO with stannous chloride absorbed about 1 mole of oxygen at 45°C, respectively. In the oxidation process, the contents of peroxide value and conjugated diene of ML-HPO decreased proportionately with oxygen uptake. MFO and malonaldehyde were found in oxidized ML-HPO. One mole of oxidized ML-HPO released 0.393 mole of MFO at maximal rate. The quantity of malonaldehyde found was about one-tenth of MFO. MFO and malonaldehyde were found in case of HODE as well as ML-HPO. Thier quantity, however were less than in case of ML-HPO.The above results indicated that MFO was not formed from ML-HPO that was the first product of autoxidation of methyl linoleate, but formed from furthermore oxidized ML-HPO.

Refractive index as an objective method for evaluation of rancidity in edible oils and fats

AbstractCommon edible oils and fats (refined peanut oil, seasame oil, safflower oil, and butter oil, ghee) were exposed to direct sunlight, fluorescent light and Schaal Test. Data collected on refractive indices (ND25) show an increase of the order of 0.001±0.0003 at the stage of development of perceptible rancid odor. The pattern of changes in refractive indices and peroxide values of these edible oils, autoxidized at 100±5 C, show that refractive indices indicate more precisely the termination of the induction periods than peroxide values.

Methods for stability and antioxidant measurement

AbstractA great variety of books and technical papers has been published dealing in detail with the basic chemistry of rancidity in fats and oils and the techniques which have been investigated as a means of determining the stability characteristics of fats and oils as well as the effectiveness of various agents, such as antioxidants, in improving those stability characteristics. This review of methods for stability and antioxidant measurement is intended to serve as a relatively brief outline of that particular area of fat and oil technology.

Action of Microorganisms on the Peroxides and Carbonyls of Rancid Fat

SUMMARY— The effects of 26 species of bacteria, molds, and yeasts on the hydroperoxides and monocarbonyls in rancid fat have been determined. All of the cultures were capable of decomposing the hydroperoxides. The activity of microorganisms on the monocarbonyl content of the rancid fat was quite varied and could be divided into: 1) microorganisms which produced large increases in at least two monocarbonyl classes; 2) microorganisms which removed 2,4‐dienals; 3) microorganisms which removed 2,4‐dienals and 2‐enals, and 4) microorganisms which caused decreases in at least two classes of monocarbonyb (without destroying completely any class).Two microorganisms produced methyl ketones, a monocarbonyl class which does not appear in rancid lard. There appeared to be a relationship between the ability to decompose peroxides strongly and the ability to produce a great increase in the monocarbonyl content. There apparently is no relationship between the ability to decompose peroxides and lipolytic activity. The possible importance of microorganisms in controlling hydroperoxides and monocarbonyls in fats is discussed.

Oxidation of Methyl Linoleate and the Influence of Antioxidants. I

In order to investigate the atomospheric oxidation of linoleic acid, which generally offers the important factor for the rancidity of edible fats, we tried to oxidize pure methyl linoleate by passing oxygen at 110°. On each sample obtained at the interval of 1-2 hours during oxidation, several chemical constants such as peroxide value (P.O.V.), carbonyl value (Car.V.), acid value (A.V.), dinitrophenylhydrazine value (D.N.P.V.), thiobarbituric acid value (T.B.A.V.), refractive index (R.I.), and iodine value (I.V.) were measured. Moreover, the changes of UV and IR absorption spectra, and gas chromatograph on these samples were examined. The results obtained were as follows : methyl linoleate at first turned into trans-trans conjugated diene, hydroperoxide was formed in this high temperature oxidizing condition, then carbonyl compounds were produced, and carboxylic acids and polymeric compounds increased gradually. Besides the antioxidation effect by the addition of BHA (concentration of 0.1, 0.2%), and synergetic effect of citric acid (0.2%) were observed in this oxidation condition. Though the above mentioned condition is rather convenient for the observation of the effect of antioxidants in a short time, it is too violent to expect precise reproducibility with some chemical constants such as P.O.V. or D.N.P.V.

Studies on Oxidative Rancidity of Fat and Oil (III)

Studies on Oxidative Rancidity of Fat and Oil (III)

Studies on Oxidative Rancidity of Fat and Oil (II)

Methyl linoleate hydroperoxide (ML-HPO) was separated from methyl linoleate autoxidized at about 10°C by the combination method of simple countercurrent extraction and column chromatography. The peroxide value of ML-HPO was more than 5, 780meq/kg. This value indicated that the material was essential pure monoperoxide. ML-HPO had a conjugated diene and a hydroperoxide group. Being hydrogenated with platinum oxide, ML-HPO absorbed 3.11 mole of hydrogen, and was converted into a mixture of great quantity of hydroxystearic acid methyl esters and slight unknown material. The methyl esters contained equal amount of 9 and 13 hydroxystearic acid methyl esters.When ML-HPO stored in air and in nitrogen at 25°C, the contents of conjugated diene and peroxide value of ML-HPO decreased respectively. This fact evidences that decomposition of ML-HPO occurred in those atmospheric conditions. Methyl 8-formyloctanoate (MFO) was detected in oxidized ML-HPO, was not detected in the substance that decomposed under nitrogen, by gasliquid chromatographic analysis.ML-HPO and hydroxyoctadecadienoic acid methyl ester (HODE) which was obtained from reduction of ML-HPO with stannous chloride absorbed about 1 mole of oxygen at 45°C, respectively. In the oxidation process, the contents of peroxide value and conjugated diene of ML-HPO decreased proportionately with oxygen uptake. MFO and malonaldehyde were found in oxidized ML-HPO. One mole of oxidized ML-HPO released 0.393 mole of MFO at maximal rate. The quantity of malonaldehyde found was about one-tenth of MFO. MFO and malonaldehyde were found in case of HODE as well as ML-HPO. Thier quantity, however were less than in case of ML-HPO.The above results indicated that MFO was not formed from ML-HPO that was the first product of autoxidation of methyl linoleate, but formed from furthermore oxidized ML-HPO.

Resistance to pentobarbital in rats fed a cachexigenic diet

A serendipitous observation disclosed that albino rats which became cachectic after several weeks of feeding a rancid, standard, biotin-deficient diet were not less but more resistant to the toxic effects of pentobarbital administered on a body weight basis. The cachexigenic diet had produced a relative increase in liver weight, so that when doses were calculated on the basis of liver weight there was no increased resistance to pentobarbital. While the availability of relatively more liver for metabolism of pentobarbital appeared to explain the phenomenon, it should be noted that the cachectic rats also had developed a stressor reaction and changes in weight of certain other organs, such as gastrointestinal tract, kidneys, skin, and muscle. The responsible factor in the cachexigenic diet appeared to be the rancid fat fraction.

Studies on Oxidative Rancidity of Fat and Oil (I)

Studies on Oxidative Rancidity of Fat and Oil (I)

Inhibiting Action of Oxidized Pork Fat on the Germination of Spores of Bacillus Subtilisa

SUMMARYRancid lard, as determined by peroxide number, iodine number, and TBA values, inhibited the germination and/or growth of Bacillus subtilis spores. As peroxide numbers and TBA values increased and iodine numbers decreased, the number of B. subtilis spores which germinated and produced visible colonies decreased at constant incubation time. This inhibitory effect may be used as a criterion of pork fat rancidity.

Girard T Reagent for Carbonyls

THE water-soluble properties of Girard T hydrazones make the reagent potentially effective for isolation of carbonyls from mixtures soluble in non-polar solvents. In work on the chemistry of rancidity1, we have found the reagent useful in learning about the distribution of volatile and non-volatile carbonyls in rancid fat. This work indicated possible usefulness of the reagent for investigation of the complex carbonyl anatomy of autoxidized fats. Successful application depends on adaptation to quantitative isolation of very small amounts of carbonyls, and on devising means of controlling the reaction so as to isolate at will free carbonyl and bound or potential carbonyl.

Rancidity of Pork

Rancidity of Pork

Rancidity of Soap

Rancidity of Soap

Volatile Saturated Aliphatic Aldehydes in Rancid Fat

Volatile Saturated Aliphatic Aldehydes in Rancid Fat

Volatile saturated aliphatic aldehydes in rancid fat.

Volatile saturated aliphatic aldehydes in rancid fat.