Data/Result: Table 1: Group 10 s starting and ending volumes of NaOH, total volume of NaOH, and weight of olive oil

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1 Determining Acidity of Olive Oils I. Purpose/Objective: The purpose is to identify percent of oleic acids in different types of olive oils. Using a prepared sodium hydroxide solution with a known normality, samples of the different olive oils were titrated to find the titratable acidities. Also, samples of each olive oil were subjected to a sensory test to compare the differences in acidity, fruitiness, color and aroma. II. III. Introduction: There are many different grades of olives oils available, each differing in flavor and quality. The grade of the olive oils depends on olive type, fruit maturity, growing region, and how the oil is extracted. Each olive oil grade has a different standard to determine the quality. The free fatty acids in the olive oil are particularly important in determining the quality. Free fatty acids are formed when lipase breaks the ester bonds bonded to the fatty acids on the triglyceride. Lipase is naturally found in olives and other fruits. It is activated when the fruit is ripe on the tree, when the fruits are left on the ground or in the collection nets for long periods of time, and when the fruit is damaged. The food industry uses a strong standard base of known concentration to the amount of free fatty acids present. In the reaction, the free fatty acids donate protons to the base. In a weak acidstrong base reaction, an indicator in the reaction can be used to find the equivalence point. At the equivalence point, there are stoichiometric amounts of the base and fatty acid in the sample. In this experiment, an indicator is used when titrating the olive oil sample with the strong base to determine the equivalence point, and thus the amount of fatty acids, of the olive oil. Procedure: This laboratory procedure is found in the Principles of Food Composition, Laboratory Manual, FST 101A (Fall 01) Lab C, Total Acidity of Olive Oils, pages 1-7. Modifications for this lab is obtaining the ml of indicator via the pre-set pump and obtaining all samples of olive oils via the pre-set pump. 1

2 IV. Data/Result: Table 1: Group 10 s starting and ending volumes of NaOH, total volume of NaOH, and weight of olive oil Olive Oil Sample V initial (ml) V final (ml) Δvolume (ml) Sample Weight (g) Extra Virgin Refined Pure Table : Calculated percent acidity for each titration, the average percent acidity of each olive oil, and standard deviation for each olive oil. Extra Virgin Olive Oil Pure Olive Oil Refined Olive Oil % Oleic acid Mean SD Table 3: ANOVA table of percent acidity Anova: Single Factor SUMMARY Groups Count Sum Average Variance Extra Virgin E-05 Refined Pure E-05 ANOVA Source of Variation SS df MS F P-value F crit Between Groups E Within Groups 9.45E E-05 Total

3 Mean % Acidity Mean % Acidity Extra Virgin Refined Pure Olive Oil Figure 1: Titration curve and the first derivative for the fourth KAP titration. V. Calculations: Total Volume = Volume final Volume initial Example: For Group 10, total volume of NaOH for Extra Virgin Olive Oil sample 1 (see Table 1) Total Volume NaOH = 3.6mLNaOH - 0.0mL NaOH Total Volume NaOH = 3.6mL NaOH % acidity = N acid * EqWt * 0.1L 100mL Example: For Group 10, % acidity of Extra Virgin Olive Oil sample 1. (see Table 1) 1 L g V Total NaOH * * 0.1 M *8 % acidity = 1000 ml mol *100 weight sample 1 L g 3.6 ml * *0.1 M *8 % acidity = 1000 ml mol * g % acidity = 0.10 g 30.5 g *100 % acidity = *100 % acidity = 0.33% 3

4 (% acidity) n -1 average % acidity = n n Example: For Group 10, average % acidity of Extra Virgin Olive Oil (see Table 1 and ) average % acidity = 3 average % acidity = average % acidity = average % acidity = 0.34 " = n $ n #1 (x i # x) N #1 Example: For Group 10, standard deviation of Extra Virgin Olive Oil (see Table 1 and )! VI. σ = ( ) + ( ) + ( ) 3 1 σ = ( ) + (0.0033) + (0.0033) σ = σ = σ = σ = Discussion: The mean percent acidity for each of the olive oils was 0.34% for extra virgin olive oil, 0.08% for refined olive oil, and 0.3% for pure olive oil. Each of these percent acidities is less than the maximum percent free acidities of less than 0.8%, less than 1.0%, and less than 0.3%, respectively for each olive oil type. When an olive oil has a high percent acidity, there are more free fatty acids present. This means that the quality of the oil is low. The extra virgin olive oil had the greatest titratable free acidity compared to the others. However, since the maximum percent of oleic acid is 0.8%, it is still within standard limits. 4

5 The calculated F value is , which is greater than the F critical value of The P-value is E-10. Since the F value is greater than the F critical value and the P-value is less than 0.05, there at least one group significantly different from another. In comparing the standard deviations, the standard deviation for extra virgin olive oil is , the standard deviation for refined olive oil is 0.00, and the standard deviation for pure olive oil is When comparing the standard deviation error bars, none overlap, which suggests that each olive oil is significantly different from another. Since each olive oil is significantly different from another, this relates to the understanding that each olive oil grade has a different maximum percent acidity. VII. VIII. Conclusions: In this laboratory experiment, an already prepared standardized NaOH base solution of known normality was used to titrate three different grades of olive oil, extra virgin, pure, and refined. By titrating these olive oil samples, the percent acidity of the fatty acids in the olive oil can be found. In the experiment, a volume of ethanol was heated, then neutralized with the NaOH solution. After, a volume of one of the olive oil grades (with known weight) was added to the ethanol. This solution was then titrated with the NaOH solution until the phenolphthalein indicator turned slightly pink, indicating the equivalence point had been met. Three trials of each type of olive oil were titrated in this experiment. Each olive oil was titrated three times to ensure an accurate equivalence point. Each member of the group participated equally in the experiment. Each person prepared the ethanol solution, prepared the olive oil samples, and titrated the olive oil with NaOH. This made the procedure go smoothly and efficiently. Questions: 1. In tasting each olive oil, I could perceive a difference in the acidities. Sample 3 was the most acidic and sample was the least acidic. The oleic acid percents were reflected in each sample. Sample 3, most likely the extra virgin olive oil, was distinctly more acidic, and had a bitter aftertaste. Sample was the least acidic olive oil and most likely refined olive oil, had practically no perceived acidic taste. However, since olive oil is made up of two additional fatty acids, linoleic acid and palmitic acid, they can also affect the tastes of the olive oil.. According to the statistical analysis, each of the olive oils are statistically different, as the F- value is greater than the F-critical value, the P-value is less than 0.05, and none of the error bars in Figure 1 overlap. 3. By basing the titratable acidity on oleic acid molecular weight, it is assumed that oleic acid is the only free fatty acid in the olive oil, or that the NaOH standard base solution is only interacting with the oleic acid and not the linoleic acid nor palmitic acid. An alternative is to 5

6 base the titratable acidity on the sum of the product of the average percent of each free fatty acid found in the particular olive oil grade and the free fatty acid s molecular weight. i.e. MW=[(Avg% oleic *MW oleic)+ (Avg% linoleic *MW linoleic)+( Avg% palmitic *MW palmitic)] 6

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