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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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. Analytical procedures Green potentiometric method Weight with at least 0.
The acid number of oils and fats is calculated through equation 1. The automatic potentiometric titration is usually done in about 5 min, whereas the point-by-point methhod needs about 30 min. Knowledge related to this subject, acquired in developing earlier methods, was applied in the present work. The acid number is a parameter that quantifies the acid products of degradation reactions of an oil or a fat.
In the green method proposed in this article, the solvent is a 1: Services on Demand Journal. During the cooking of the food submitted to frying, the triacylglycerols are degraded as a consequence of the high temperature, of metho loss of water and of exposure to the oxygen of the air. Therefore, the determination of their concentrations throughout the refining process and during the storage is important for monitoring the occurrence of degradation reactions.
A green potentiometric method for determination of the acid number of oils and fats. The potentiometric titration curves obtained for the oils and for swine lard are quite similar to those seen in Figure 1and therefore, the end point is easily determined. It can also react with water.
The presence of free fatty acids is undesirable in oils and fats as it reflects the nutritional quality of the product. 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. Acs and fats are compounds that are constituted of esters formed by fatty organic acids linked to a molecule of glycerol, forming triacylglycerols.
Mean relative standard deviation for the proposed procedure was 2. All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License.
aocs official method cd 3d-63 pdf
Introduction Oils and fats are compounds that are constituted of esters formed by fatty organic acids linked to a molecule of glycerol, forming triacylglycerols. This situation not only reduces the time of the analysis, but also minimizes the possible effect of dehydration of the electrode as it remains for a shorter period in contact with the 1: 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.
In conformity with Table 2this disagreement is caused by the higher imprecision of the AOCS method with respect to the here proposed. 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. The sample is dissolved in a water-ethanol mixture 1: As can be seen in the results presented in Table 2the calculated slopes and the intercepts are close to the ideal 1 and 0, respectively, in all cases.
Potentiometrically titrate with 0.
Nova, 23 offifial, The electrodes were calibrated as usual with aqueous buffer solutions of pH 7. The sample is then added and the obtained solution is aocz under vigorous shaking throughout until the moment a pink color that persists for 30 s is observed.
With respect to the precision of the methods, it is clear that the green potentiometric procedure herein proposed presents the best performance. 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. All the reagents and solvents were of analytical grade. It is expressed in mg of KOH per g of sample. It also furnishes equivalent results to those obtained by the visual green aocw with the advantage that the end point of the titration is determined instrumentally.
The foficial must be frequently rehydrated or the electrode can be irreversibly damaged. For the castor oil, however, no concordance was found. 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.
For the comparison of the precisions of the methods, the F -test was applied. The potentiometric method herein proposed was performed point-by-point and also using an automatic titrator in order to obtain the acid number of the aoc. April 4, Published online: 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 study. The acid number of the 75 mL of solvent blank value must be obtained by a similar titration.
The acid number of oils and fats is determined through the titration of the sample with a standardized 0. It was observed in the present work, that after about 10 titrations, it is advisable to keep the electrode immersed in a 0. Soy, corn, canola, sunflower, linseed and castor oils and swine lard used in methor present study were purchased at local markets. Collins for English revision of the manuscript. The shorter time methld the automatic procedure means, as an evident consequence, that the glass membrane remains in contact with the solution for a shorter time interval in comparison with the point-by-point titration.
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: Considering the above observations, the green method developed in this work can be proposed officoal the routine determination of the acid number of oils and fats. An ultrasonic bath was used to degasify solvents and solutions. A green titrimetric method using potentiometry is proposed for determination of the acid number of vegetable oils and animal fats.
This solvent mixture is previously neutralized with the standard KOH solution using 33d-63 until the appearance of a slight pink color.
aocs official method cd 3d pdf – PDF Files
No evidence for systematic differences between the different sets of results was observed, offjcial in the case of the comparison between the AOCS and the ABNT methods. After each titration, carefully rinse the electrode with small portions of ethanol total of 15 mL to remove traces of oil or fat, followed by washing with distilled water, and immerse the electrode in distilled water for 1 min to rehydrate the glass membrane.
Conclusion The green potentiometric method for the determination of the acid number of oils and fats herein proposed furnishes similar but more alcs and precise results to those obtained by the AOCS Cd 3d and by the ABNT-NBR methods that use organic solvents, such as toluene, ,ethod as titrant a KOH solution in isopropyl alcohol.