Methods. Known throughout the world as the most comprehensive collection of for fats and oils, the Official Methods and Recommended Practices of the AOCS Find and purchase methods from the Official Methods and Recommended. cation of the AOCS Cd 3d method, through a statistical . Methods. AOCS Cd 3d Official Method [8]. The acid number in oils and fats is determined. ufacturing, Kyoto, Japan) according to the AOCS Official. Method Cd 3d [23]. All AV analysis results were expressed as mg KOH/g oil.

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The solutions of the bases were stored in alkaline resistant bottles. The acid number is calculated using equation 1. Nova, 23Mean relative standard deviation for the proposed procedure was 2. An ultrasonic bath was used to degasify solvents and solutions.

aocs official method cd 3d-63 pdf

The acid number is a parameter that quantifies official acid products of degradation reactions of an oil or a fat. Potentiometrically titrate with 0. In conformity with Table 2this disagreement is caused by the higher imprecision of the AOCS method with respect to the here proposed.

This fact can be attributed to the tendency of the AOCS method to produce higher results because mehhod the difficulty in the accurate determination of the end point of the visual titration of a colored sample. This non aqueous potentiometric offivial presents as a disadvantage the use of organic solvents that, besides the toxicological and environmental problems of the solvents, also causes the dehydration of the glass membrane of the electrode.

A Metrohm model pH meter and a Metrohm Titrando titrator were used to perform, respectively, point-by-point and automatic titration. Soy, corn, canola, sunflower, linseed and castor oils and swine lard were used in the present offiial. The other methods present similar standard deviation among them with a little lower value for RSD mrthod green visual procedure.

These reactions cause the breaking of the triacylglycerol molecule leading to the formation of free fatty acids which are responsible for the unpleasant flavor characteristic of the oxidized fats as for example, rancid butter. The acid number is calculated using equation 1 where A is the titrant solution volume mL used in the titration of the sample, B is the titrant solution volume mL used in titration of the blank.


A green potentiometric method for determination of the acid number of oils and fats

Therefore, the present work has as objective to apply potentiometric detection to the titrimetric method aiming at low cost, operational simplicity and, especially, as environmentally friendly procedure.

In order to verify the stability of the basic titrant solutions, 0. Weight with at least 0. In order to verify the accuracy of the potentiometric procedure developed with respect to the AOCS Cd 3d and to the two other applied methods, a statistical weighted linear regression procedure was used.

For linseed, no statistical concordance was observed. The membrane must be frequently rehydrated or the electrode can be irreversibly damaged. It was observed in the present work, that after about 10 titrations, it is advisable to keep the electrode immersed in a 0.

It is expressed in mg of KOH per g of sample.

No evidence for systematic differences was observed. Because of the above observations, it is evident that the precision of the proposed green potentiometric method is higher than of the all others here used for comparison.

No evidence for systematic differences between the different sets of results was observed, except in the case of the comparison between the AOCS and the ABNT methods. Considering the above observations, the green method developed in this work can be proposed for the routine methoc of aics acid number of oils and fats. Rapid preventive rehydration methos min is enough to maintain the membrane of the electrode in good conditions.

For the comparison of the precisions of the methods, the F -test was applied. Then, it is placed in distilled water for 5 min to rehydrate the glass membrane. The quantity of these acids indicates how the feedstock was treated during industrial processing and during the storage. The sample is then added and the obtained solution is titrated under vigorous shaking throughout until the moment a pink color that persists for 30 s is observed. The presence of free fatty acids is undesirable in oils and fats as cf reflects the nutritional quality of the product.

Therefore, the determination of their concentrations throughout the refining process and during the storage is important for monitoring the occurrence of degradation reactions.

Analytical procedures Green potentiometric method Weight with at least 0.

aocs official method cd 3d pdf – PDF Files

Soy, corn, canola, sunflower, linseed and castor oils and swine lard used in the present study were purchased at local markets. The potentiometric titration curves obtained for the oils and for swine lard are quite similar to those seen in Figure 1and therefore, offficial end point is easily determined.


Weigh the sample directly into a mL tall form beaker. In the hydrolytic rancidity reactions, the carboxylic group suffers the action of enzymes of a microbial order commonly found in oleaginous seeds. Reagents, solutions and solvents All the reagents and solvents were of analytical grade.

The shorter time of the automatic procedure means, as an evident consequence, that the glass membrane remains in contact with the solution for a shorter time interval in 3r-63 with the point-by-point titration. Using a graduated cylinder, add 75 mL of the 1: The proposed green potentiometric procedure presents less toxic characteristics than the official procedures as it uses ethanol and water as solvents in place of isopropyl alcohol and toluene and therefore is greener.

Knowledge related to this subject, acquired in developing earlier methods, was applied methd the present work. Introduction Oils and fats are compounds that are constituted of esters formed by fatty 3dd-63 acids linked to a molecule of glycerol, forming triacylglycerols.

Oils and fats are compounds that are constituted of esters formed by fatty organic acids linked to a molecule of glycerol, forming triacylglycerols.

The usual method for its determination is the AOCS Cd 3d AOCS, procedure, in which the sample is dissolved in toluene and isopropyl alcohol and a visual titration is performed with a 0. Conclusion The green potentiometric method for the determination of the acid number of oils and fats herein proposed furnishes similar but more accurate and precise results to those obtained by the AOCS Cd 3d and by the ABNT-NBR methods that use organic solvents, such as toluene, and as titrant a KOH solution in isopropyl alcohol.

Collins for English revision of the manuscript. It should be noted that this method was originally proposed for the determination of the acid number of mineral oils and of biodiesel.