P-Anisidine Value

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. 

Anisidine value. The p-anisidine value (p-AnV) measures the amount of unsaturated aldehydes in fats and oils. In this method, p-anisidine reacts with aldehydes in acetic acid to afford a yellowish color that is measured at 350 nm. The color intensity depends on the amount of aldehydes as weU as on their structure. The AOCS Method Cd 18-90 (22) has been standardized for anisidine value analysis. The Totox value, which is 2 PV + p-AnV, provides information about the current status of oxidation as well as its history and is used by the industry. 

As aldehydes and some ketones have long been identified as oxidation and breakdown products of fats, their determination also has been common in soybean oil quality control. The p-anisidine value (300) measures light absorbance of aldehydes, primarily 2-alkenals, and 2,4-dienals at 350 nm. However, this measure is not entirely specific, because the color intensity developed depends not only on the concentration but also on the structure of the aldehyde. Therefore, the results are comparable only within oils of similar type and treatment (304). 

AOCS has a recommended practice (Cg 3-91) for assessing oil quality and stability (AOCS, 2005) for measuring primary and secondary oxidation products either directly or indirectly. For example, peroxide value analysis (AOCS method Cd 8-53) (AOCS, 2005) determines the hydroperoxide content and is a good analysis of primary oxidation products. To determine secondary oxidation products, the procedure recommends p-anisidine value (AOCS Method Cd 18-90, 2005) volatile comlb by gas chromatography (AOCS Method Cg 4-94, 2005) and flavor evaluation. (AOCS Method Cg 2-83, 2005). The anisidine value method determines the amounts of aldehydes, principally 2-alkenals and 2, 4-dienals, in oils. The volatile compound analysis method measures secondary oxidation products formed during the decomposition of fatty acids. These comlb can be primarily responsible for the flavors in oils. The... 

Determination oe Secondary Oxidation Products ("Oee-Feavor" Voeatiees) 12.2.2.1 p-Anisidine Value Test... 

The para-anisidine value (PAV) is defined as 100 times the absorbance of a solution resulting from the reaction of 1 g of fat or oil in 100 mL of a mixture of solvent and p-anisidine, measured at 350 nm in a 10 mm cell. A drawback of the method is that nonvolatile aldehydes also, for example 2,5 oxo-glycerides, can contribute to the absorption. As a rule of thumb, it can be said that good quality oil should have a PAV of less than 10. A good correlation between the p-anisidine value of salad oils and their organoleptic scores has been rqxtrted in the literature. ... 

The so-called TOTOX value has been used as an oxidative indicator, combining peroxide (POV) and p-anisidine values (PAV) as follows ... 

Phosphatides (as P) Moisture Peroxide value p-Anisidine value... 

The only difference between the method described here and the lUPAC method is that lUPAC indicates the anisidine value as p-anisidine value (p-AV). 

Catalysis by DABCO in the reactions of FDNB with piperidine, r-butylamine, aniline, p-anisidine and m-anisidine (usually interpreted as base catalysis as in Section B) was also assumed to occur by the formation of a complex between DABCO and the substrate14913. The high (negative) p-value of —4.88 was deemed inappropriate for the usually accepted mechanism of the base-catalysed step (reaction 1). For the reactions with p-chloroaniline, m- and p-anisidines and toluidines in benzene in the presence of DABCO a p-value of —2.86 was found for the observed catalysis by DABCO (fc3DABC0). The results were taken to imply that the transition state of the step catalysed by DABCO and that of the step catalysed by the nucleophile have similar requirements, and in both the nucleophilic (or basicity) power of the nucleophile is involved. This conclusion is in disagreement with the usual interpretation of the base-catalysed step. 

Other indices measure a secondary stage of oxidation, such as the anisidine value (ANV), pointing to formation of carbonyl compounds, capable of undergoing condensation reactions with p-anisidine, and the thiobarbituric acid reactive substance (TBARS) pointing to the presence of malondialdehyde (MDA) in particular. In biological systems, TBARS is of widespread use as a measure for the extent of oxidation damage. Another test for stability of oils to oxidation is based on the development of acidity as secondary product, for example, standards using the Rancimat equipment or a similar setup. 

White, P.J. 1995. Conjugated diene, anisidine value, and carbonyl value analyses. In Methods to Assess Quality and Stability of Oils and Fat-Containing Foods (K. Warner and N.A.M. Eskin, eds.) pp. 159-178. AOCS Press, Champaign, 111. 

Figure 3.32. A change in the initial distribution of electron transfer distances Y(r) = cmo(r) with the encounter diffusion coefficient D. Ions are produced in 9,10-dicyanoanthracene (DCA, fluorescer) + p-anisidine (ANS, quencher) encounters at c = [ANS] = 0.3 M. The value of D is 4.6 x 10-5 cm2/s in acetonitrile and 0.094 x 10 5cm2/s in ethylene glycol. The parameters of Wi(r) were determined experimentally [90] and used in Ref. 27 to obtain these distributions.

Despite it limitations, the TBA test provides an excellent means for evaluating lipid oxidation in foods, especially on a comparative basis. However, its use in bulk oils is less common than the so-called para-anisidine value (p-AnV) detailed below. 

The benzidine or anisidine value method uses the reaction of nonvolatile a- and p-unsaturated aldehydes with these reagents (42, 43). Absorption readings are made at 350 nm in 1-cm cells. Originally, benzidine was used as a reagent. Later, because of the carcinogenicity of benzidine, anisidine was recommended. This method of determining the degree of oxidation is extensively used in Europe and... 

There are surprisingly few alkoxyanilines for which thermochemical data seemingly exist. The simplest compounds are 2- and 4-methoxyaniline, known also as o- and p-anisidine. For the former compound, Reference 81 reports an enthalpy of formation of —46 kJmol-1 for the solid. For the latter, Reference 5 chronicles a value of —172 kJ mol-1, also for the solid. These two values are incomprehensively incompatible with each other. They are also incompatible with an enthalpy of formation derived from equation 2, ca —132 kJmol-1 (using—114.8 kJmol-1 for the enthalpy of formation of liquid anisole). 

Table 7.1 Ee values for Ir based reductive amination of acetophenone derivatives with p anisidine.

Among the simple methods for carbonyl compound determination, the anisidine value (AsV) is quite popular. The method involves a color reaction between carbonyl compounds and p-anisidine. The anisidine value is a combined measurement of... 

The MI energy values were calculated using the model carbon phase shown in Figure 6.9, with p-anisidine on the model phase. The calculated energy values are summarized in Table 6.6. 

In the lUPAC method 2.504 (Paquot, 1979a) it is noted that p-anisidine in the presence of acetic acid reacts with aldehydic components in oils or fats. The intensity of the colour of the yellowish reaction product formed depends not only on the amount of aldehydic components present but also on their structure. It has been found that a double bond in the carbon chain conjugated with the carbonyl double bond increases the molar absorbance four to five times. This means that 2-alkenals, in particular, will substantially contribute to the value found. 

To avoid having to refer continually to other texts, and to ensure that the reader appreciates that the techniques used in the formation of reaction models are common to all branches of reaction engineering, this chapter begins by introducing some basic concepts of reaction kinetics. (For a more detailed treatment the reader should consult Refs. 1-4.) We will then derive some simple kinetic relationships and discuss reaction models and experimental methods of obtaining numerical values for the kinetic constants involved. The chapter concludes by giving two examples of reaction models, one for the reduction of hexavalent uranium to a four-valent state and the other for electrosynthesis of p-anisidine from nitrobenzene. 

The ultimate quality of refined cosmetics oil will depend strongly on the characteristics of the starting material. The quality of a processed oil is usually evaluated by the following factors Free fatty acids (%) peroxide value anisidine value color flavor metals (Fe, Ca, Mg, P) water content and results from gas chromatographic analysis... 

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for the 0- and p-isomers of anisidine is 0.1 ppm (0.5 mg/m ). 

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