Lab 2.3- Titratable Acidity of Extra Virgin, Pure, and Extra Light Olive Oils PURPOSE: INTRODUCTION: PROCEDURE:

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1 Christina Stapke Thurs 2:10-5 F.C. Lab 2.3- Titratable Acidity of Extra Virgin, Pure, and Extra Light Olive Oils I. PURPOSE: The purpose of this lab was to evaluate the titratable acidities of the different olive oils by titration with a standardized sodium hydroxide solution. The acidities were calculated by referring to oleic acid as the dominant acid in the three different olive oils. This determination will also assess the quality of the three olive oils relative to one another. II. INTRODUCTION: To determine the percent acidities, the olive oils were combined in an ethanol solution and titrated with a standardized solution of sodium hydroxide. This way the acidities were evaluated with respect to the amount of strong base added, using oleic acid as the most abundant in olive oil to determine the percent composition. Extra Virgin olive oil is the oil obtained from the fruit of olive trees, without the use of heat or solvents. Flavor compounds and polyphenols are conserved in this lack of refining or processing. It has a free acidity of less than 0.8%. Olive oil, or the Pure oil used in this experiment, is a blend of refined and unrefined virgin oils. It represents the bulk of the olive sold on the world market to consumers and should not have a free acidity of more than 1%. Refined olive oil, or the Extra Light used in this experiment is obtained from virgin oils that are refined through a series of processes to rid the oil of undesirable tastes and odors. It should have a free acidity of less than 0.3%. The test of acidity in the different oils is very important in the food industry in terms of correctly labeling and pricing the different oils. For example, Extra Virgin olive oil should be priced higher due to a lower free fatty acid content. III. PROCEDURE: The procedure followed for the experiment is found in Principles of Food Composition Laboratory Manual (2013) Experiment 3, Total Acidity of Olive Oils, pages Modifications included using pre-measured amounts of oil and

2 indicator from dispensers, heating the ethanol until being able to see a convection current, and repeating all steps three times for each of the olive oils. IV. DATA/RESULTS: Table 1: Starting, ending and total volumes of the amounts of sodium hydroxide added for each of the three titrations of Extra Virgin, Pure and Extra Light Olive Oils. Olive Oil Titration # Starting Volume (ml) Ending volume (ml) Total NaOH added (ml) Extra Virgin Pure Extra Light Table 2: Percent oleic acid with the corresponding averages and standard deviations for each of the three titrations of Extra Virgin, Pure, and Extra Light Olive Oils. Titration Extra Virgin (%) Pure (%) Extra Light (%) Average SD Table 3: ANOVA values for the titratable acidities of each olive oil. SUMMARY Groups Count Sum Average Variance Extra Virgin E-07 Pure Extra Light ANOVA Source of Variation SS df MS F P-value F crit Between E- Groups Within Groups Total

3 Table 4: Olive oil sensory rankings of deepness of green color, aroma, sourness/acidity, and fruitiness/nuttiness of Extra Light, Pure, and Extra Virgin olive oils. [1= greatest ranking] Deepness Oil # Type of Olive Oil of Green Color Deepness of Aroma Sourness/Acidity Fruitiness/Nuttiness 1 Extra Light Pure Extra 3 Virgin Fig. 1 Titratable Acidities of Olive Oils Average % Acidity EVOO POO ELOO Figure 1: Averages of percent acidity with standard deviation indicated by the error bars for Extra Virgin (blue), Pure (red), and Extra Light (yellow) olive oils.

4 V. CALCULATIONS: a. Total Volume of NaOH added for Extra Virgin Olive Oil for Titration 1: Total Volume NaOH (ml) = Final Volume of NaOH (ml) Initial volume NaOH (ml) Total Volume NaOH= 2 ml 0 ml = 2 ml b. % Acidity of Titration 1 of Extra Virgin Olive Oil: % acid= [(V NaOH ml x 1L/1000mL x [NaOH] M x MW acid g/mol]/ Test Portion g] x 100 % acid= [(2.000 ml x 1L/1000mL x M x g/mol)/27.60 g] x 100= % c. Average % Acidity for Extra Virgin Olive Oil: Avg % acidity= (% 1 + % 2+ % 3)/3 Avg % acidity= ( )/3.000 = % d. Standard Deviation for % Acidity for Extra Virgin Olive Oil SD= ((% 1- avg)^2 + (% 2 avg)^2 + (% 3 avg) ^2)/(n 1) SD= (( )^2 + ( )^2 + ( )^2)/ ( ) SD= % VI. DISCUSSION: The results for the highest percent oleic acid were as expected with the Extra Virgin having the highest acidity, which was followed by the Pure and Extra Light oils. The Pure and Extra Light were closer in percent acidity but still proved to be significantly different. According to the ANOVA statistics, the titratable acidities of the Extra Virgin, Pure, and Extra Light olive oils were significantly different. To show at least one group is significantly different from another, there is a much greater F value than F critical value, along with the P value being less than In addition, each group proved to be significantly different than the other in their non-overlapping standard deviations of the three averages. Furthermore, the sensory test for acidity somewhat correlates with the percent acidities obtained from the three different olive oils. The Extra Virgin olive oil tasted the most acidic, had the deepest aroma and color, and was the fruitiest/nuttiest, in which it also proved to contain the most oleic acid. On the other hand, the Extra

5 Light tasted more acidic (also had a deeper aroma, color, and tasted fruitier/nuttier) than the Pure olive oil, which had a higher percent acidity. VII. CONCLUSION: The percent oleic acid in the Extra Virgin, Pure, and Extra Light olive oils was determined by titration with sodium hydroxide and compared to their respective quality and taste. The differences in acidities were determined significant by a Analysis of Variance (ANOVA) test. A regular T-test was not used because there were more than two groups being compared. It was interesting to see that the more acidic taste of the Extra Light olive oil did not correspond with it having a smaller percent acidity than the Pure olive oil. VIII. QUESTIONS: 1. Yes, I could perceive a difference in acidity among the three samples of olive oil. The Extra Virgin was the most acidic, followed by the Extra Light, then lastly the Pure olive oil. The percent oleic acid does not reflect all the differences in the oils- polyphenol content is an important component which gives the Extra Virgin oil the astringency and bolder taste than the others. In addition, higher free fatty acid content lowers the quality of the oil. 2. Based on the ANOVA analysis, there were significant differences in percent oleic acid content among the Extra Virgin, Pure, and Extra Light olive oils due to the F value being substantially greater than the F critical value (and the P value less than 0.05) as well as the standard deviations not overlapping. 3. In basing the titratable acidities off of the molecular weight of oleic acid, we are assuming that oleic acid is the most dominant acid in each of the olive oils. Since it is the most abundant acid it is the best approach compared to the alternative of using other

6 acids present such as linoleic and palmitic acid, which contribute a smaller percentage to olive oil composition.