Active oxygen method

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

Active Oxygen Method," Technical Data Bulletin ZG-159c, Eastman Chemical Products, Inc., Kingsport, Term., Mar. 1985. 

Rancidity measurements are taken by determining the concentration of either the intermediate compounds, or the more stable end products. Peroxide values (PV), thiobarbituric acid (TBA) test, fatty acid analysis, GC volatile analysis, active oxygen method (AOM), and sensory analysis are just some of the methods currently used for this purpose. Peroxide values and TBA tests are two very common rancidity tests however, the actual point of rancidity is discretionary. Determinations based on intermediate compounds (PV) are limited because the same value can represent two different points on the rancidity curve, thus making interpretations difficult. For example, a low PV can represent a sample just starting to become rancid, as well as a sample that has developed an extreme rancid characteristic. The TBA test has similar limitations, in that TBA values are typically quadratic with increasing oxidation. Due to the stability of some of the end-products, headspace GC is a fast and reliable method for oxidation measurement. Headspace techniques include static, dynamic and solid-phase microextraction (SPME) methods. Hexanal, which is the end-product formed from the oxidation of Q-6 unsaturated fatty acids (linoleate), is often found to be a major compound in the volatile profile of food products, and is often chosen as an indicator of oxidation in meals, especially during the early oxidative changes (Shahidi, 1994). 

The OSI replaced the Active Oxygen method (AOM), which is no longer recommended by the American Oil Chemists Society. The AOM required frequent measurement of peroxide value. Not only was this laborious, but determining peroxide value resulted in a... 

Active Oxygen Method (AOM), 535, 544 Adsorption, and interfacial properties diffusion and kinetic controlled models, 617-618 (figs.), 620-622 Gibbs adsorption isotherm, 617-619 kinetics of surface-active substances, 639... 

Laubli, M.W and Bruttel, P.A.(1986) Determination of the oxidative stability of fats and oils comparison between the active oxygen method and the rancimat metho lm. Oil Chem. So,c.63 792-795. 

In a study by Chipault et al. (1952) to test the stabilizing effect of 36 different spices on lard by the active oxygen method... 

Active Oxygen Method for Fat Stability (AOM) (Cd 12-57) determines the time (in hours) for a sample of fat or oil to attain a predetermined peroxide value (PV) under the conditions of the test. The method is used to estimate the comparative oxidative stability of fats and oils. The method has been placed in surplus, in favor of Cd 12b-92 (Oil Stability Index), but retains official status and is still used in domestic industry. p-Anisidine Value (AV) (Cd 18-90) determines the amount of aldehydes (principally 2-alkenals and 2,4-dienals) in animal and vegetable fats and oils. These are degradation products of peroxides, which are not removed by bleaching. Some fats and oils chemists propose increased use of this method in purchase specifications. Bleaching Test for Soybean Oil (Cc 8e-s63) determines the color of a sample of soybean oil after treatment with a specified bleaching earth. Specific methods exist for other oil species. 

Stability (Active Oxygen Method) Not less than 50 h. Unsaponifiable Matter Not more than 1.5%. 

STABILITY (Active Oxygen Method) (Based on AOCS Method Cd 12-57)... 

Table 2-25 Active Oxygen Method (AOM) Time of Several Oils and Fats as Determined by Peroxide Value and Conductivity Measurements...

Shelf stability test Shelf life is predicted by the active oxygen method (AOM). The fat or oil is subjected to an accelerated oxidation test under standardized conditions so that the signs of deterioration are revealed within several hours or days. The sample is heated at 97.8°C while air is blown through it. The AOM value is reported as the number of hours to reach a peroxide value of 100 meq/kg. 

Active oxygen method (AOM) Bubbling air in a closed environment, 98°C, do not represent normal storage Rancimat is the automated version, also OSI instrument... 

More than 90% of the fatty acids of coconut oU are saturated. This accounts for its low iodine value ranging from 7 to 12. The saturated character of the oil imparts a strong resistance to oxidative rancidity. Assessment of the oil by active oxygen method (AOM) yielded results between 30 h and 250 h (24). Although oxidative stability is reduced in RBD oils, due to losses in the natural antioxidants of crude coconut oils, the addition of citric acid at the end of deodorization as the oil is cooled to 100°C was effective in regaining considerable oxidative stability in the oil (25). 

AOM Stability. The active oxygen method (AOM) is the most commonly used analytical method for measuring oxidative stability of fats and oUs products. AOM employs heat and aeration to accelerate oxidation of the oil by continuously bubbling air through a heated sample. Periodic peroxide value analyses are performed to determine the time required for the oil to oxidize under the AOM conditions. This method requires close attention to detail to produce reproducible results, and even then, the variation between laboratories is 25 for a 100-hour AOM sample. 

Stability (active oxygen method), 8-h AOM Peroxide values less than 10... 

Several temperature-catalyzed stability tests are used in evaluating the oxidative stability of oils and fats. The oldest method is the Schaal oven test (39). It is inexpensive but subjective, because it uses organoleptic and odor intensities in the procedure and still requires days to obtain the result. This approach has been standardized into a recommended practice (AOCS method Cg 5-97). In the active oxygen method (AOM) (39), the development of peroxide is measured with time. As the formation and decomposition of peroxides are dynamic processes, the results obtained by this method do not correlate well to the actual stability of the oils and fats observed under practical application conditions. Other methods that have been based on oxygen absorption are the gravimetric (59) and the headspace oxygen concentration measurement (60, 61). 

Fat oxidative stability is measured by the active oxygen method (AOM, AOCS Method Cd 12-57). Oil or fat is held at 97.8°C while air is bubbled through it. The time required to develop a peroxide concentration of 100 meq/kg is the AOM stability of the sample. A closely related method, the oil stability index (OSI, AOCS Method Cd 12b-92), also bubbles air through hot oil. One of the breakdown products is formic acid, which is trapped in a water cell. The machine continuously monitors conductivity of the water, and records the time when it rises sharply. Rancimat times obtained at 110°C are 40-45% of the AOM times, so an OSI stability of 4 h is equal to an AOM stabihty of 10 h. 

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