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 . The acid number in oils and fats is determined. ufacturing, Kyoto, Japan) according to the AOCS Official. Method Cd 3d . All AV analysis results were expressed as mg KOH/g oil.
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It also furnishes equivalent results to those obtained by the visual green method with the advantage that the end point of the titration is determined instrumentally. No evidence for systematic differences was observed. According to this method, a quantity of the sample, which varies with its acidity, is dissolved in mL of a solvent that is a 1: The electrodes were calibrated as usual with aqueous buffer solutions of pH 7. How to cite this article. The acid number of oils and fats is calculated through equation 1.
This solvent mixture is previously neutralized with the standard KOH solution using phenolphthalein until the appearance of a slight pink color. For the comparison of the precisions of the methods, the F -test was applied.
AOCS Cd 3d official method During the cooking of the food submitted to frying, the triacylglycerols are degraded as a consequence of the high temperature, of the loss of water and of exposure to the oxygen of the air. The sample is dissolved in a water-ethanol mixture 1: It should be noted that this method was originally proposed for the determination of the acid number of mineral oils and of biodiesel.
This non aqueous potentiometric titration 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 green potentiometric method for determination of the acid number of oils and fats.
Considering the above observations, the green method developed in this work can be proposed for the routine determination of the acid number of oils and fats. Recently a green visual titrimetric method was presented for the determination of the acid number of oils and fats, using as titrant an aqueous 0.
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. A Metrohm model pH methood and a Metrohm Titrando titrator were used to perform, respectively, point-by-point and automatic titration.
In the hydrolytic rancidity reactions, the carboxylic group suffers the action of enzymes of a microbial order commonly found in oleaginous seeds. The proposed green potentiometric procedure presents less toxic characteristics than the mefhod procedures as it uses ethanol and water as solvents in place of isopropyl alcohol and toluene and therefore is greener.
Potentiometrically titrate with 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. The acid number of oils and fats is determined through the titration of the sample with 3-d63 standardized 0. Introduction Oils and fats are compounds that are constituted of esters formed by fatty organic acids linked to a molecule of glycerol, forming triacylglycerols.
In order to verify the stability of the basic titrant solutions, 0. Reagents, solutions and solvents All the reagents and solvents were of analytical grade. No evidence for systematic differences official the different sets of results was observed, except in the case of the comparison between the AOCS and the ABNT methods. As can be seen in the results presented in Table 2the calculated slopes and the intercepts are close to offocial ideal 1 and 0, respectively, in all cases.
A green titrimetric method using potentiometry is proposed for determination of the acid number of vegetable oils and animal fats. The acid wocs of the 75 mL of solvent blank value must be obtained by a similar titration.
aocs official method cd 3d pdf – PDF Files
Canola, sunflower, linseed, castor, corn and soy oils as well as swine lard, a total of twelve real samples, were analyzed. Therefore, the determination of their concentrations throughout the refining process and during the storage is important for monitoring the occurrence of degradation reactions.
The obtained concentrations were standardized through automatic potentiometric titration using potassium biphthalate as primary standard. April 4, Published online: Reagents, solutions and solvents. 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. For linseed, no statistical concordance was observed. This can be attributed to the fact that it is more difficult to determine the end point of the titration with the official method than in the other cases. Table 1 shows the acid numbers obtained for swine lard and for the vegetable oils canola, sunflower, linseed, castor, corn and soy applying the AOCS Cd 3d, the ABNT-NBRthe green visual 25 and the proposed potentiometric methods.
aocs official method cd 3d-63 pdf
Collins for English revision of the manuscript. The green potentiometric method for the determination of the acid officoal 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.
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. With officiaal to the precision of the methods, it is clear that the green potentiometric procedure herein proposed presents the best performance. Nova, 23Solutions of sodium hydroxide and of potassium hydroxide were prepared by dissolving adequate masses of the bases in water.
The acid number is a parameter that quantifies the acid products of degradation reactions of an oil or a fat.