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 quantity of these acids indicates how the feedstock was treated during industrial processing and during the storage. Introduction Oils and ofticial are compounds that are constituted of esters formed by fatty organic acids linked to a molecule of glycerol, forming triacylglycerols.

All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License. London, UK,p. Nova28An ultrasonic bath was used to degasify solvents and solutions.

The acid number of oils and fats is calculated through equation 1. 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. 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. Then, aofs is placed in distilled water for 5 min to rehydrate the glass membrane.

High concentrations mean loss of money as the rating of the product decreases. Nova, 23The electrodes were calibrated as usual with aqueous buffer solutions of pH 7.

aocs official method cd 3d-63 pdf

This solvent mixture is previously neutralized with the standard KOH solution using phenolphthalein until the appearance of a slight pink color.

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Collins for English revision of the manuscript. The automatic potentiometric titration is usually done in about 5 min, whereas the point-by-point procedure needs about 30 min. With respect to the precision of the methods, it is clear that the green potentiometric procedure herein proposed presents the best performance. 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.

The presence of free fatty acids is undesirable in oils and fats as it reflects the nutritional quality of the product. In the hydrolytic rancidity reactions, the carboxylic group suffers the action of enzymes of a microbial order commonly found in oleaginous seeds. 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.

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. Mean relative standard deviation for the proposed procedure was 2. 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 solutions of the bases were stored in alkaline resistant bottles.

It was observed in the present work, that after about 10 titrations, it is advisable to keep the electrode immersed in a 0. Conclusion The green potentiometric method for the determination of the 3d-663 number of oils and fats herein proposed furnishes similar but more accurate and oacs 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.

It should be noted that this method was originally proposed for the determination of the acid number of mineral oils and of biodiesel. A green titrimetric method using potentiometry is proposed for determination of the acid number of vegetable oils and animal methof.

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Solutions of sodium hydroxide and of potassium hydroxide were prepared by dissolving adequate masses of the bases in water. 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 officil other cases.

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

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

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. For the comparison of the precisions of the methods, the F -test was applied.

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. The acid number of oils and fats is determined through the titration of the sample with a standardized 0. How to cite this article. Soy, corn, canola, sunflower, linseed and castor oils and swine lard were used in the present study.

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. For linseed, no statistical concordance was observed.