What Type of Orange Juice has the Most Vitamin C? Introduction Question: What type of orange juice has the most vitamin c? Hypothesis: Freshly squeezed orange juice will have the most vitamin C compared to the other types of orange juice and drinks, because the fruit is picked fresh, and it is not stored, preserved or exposed to oxygen. Materials i. Vitamin C Indicator Solution a) One tablespoon of cornstarch b) Water c) 250 milliliters of boiling water ii. Two percent iodine solution iii. Medicine dropper. iv. (6) Disposable pipettes. v. (1) Stirring rod. vi. Cheesecloth vii. Distilled water viii. Masking tape x. Permanent marker x. Small funnel xi. Chemical safety goggles xii. Lab apron xiii. Rubber (latex) gloves xiv. Soluble starch xv. 50 mL graduated cylinder xvi. 500 mL graduated cylinder xvii. 50 mL Ehrlenmeyer flask xviii. 50 mL buret xix. Ring stand xx. Buret clamp xxi. 1/4 teaspoon measuring spoon, xxii. Glass jars for iodine (300 mL) and starch solutions. xxiii. Sources of vitamin C: a) (2) Tropicana Pure Premium 100% Pure and Natural Orange Juice (Bottled) b) (2) (Frozen) c) (2) Florida’s Natural Premium Orang Juice (Canned) Procedure Independent Variable: Orange Juice: Frozen, Canned, and Bottled. a)Tropicana Pure Premium 100% Pure and Natural Orange Juice (Bottled) b) Tropicana Season’s Best Frozen Orange Juice Concentrate (Frozen) c) Florida’s Natural Premium Orang Juice (Canned) Dependent Variable: Amount of vitamin C in each cup. (mL) Constants: Amount of orange juice, amount of solution put in each cup of orange juice. i. Wear gloves, chemical safety goggles, and a lab coat or apron when using the iodine solutions in this experiment. ii. Dilute the solution 1:10 in distilled water to make your iodine titration solution. iii. Make a starch indicator solution. a. Take one tablespoon of cornstarch and water and make into paste. . Add 250 mL of water and boil. c. Add 10 drops of this solution to 75 mL of hot water consistently as you are stirring. iv. Make a fresh vitamin C standard solution (1 mg/mL). Do this on each day that you make vitamin C measurements from orange juice. v. Titrate 25 mL of vitamin C standard solution. a. Use a clean 50 mL graduated cylinder to measure 20 mL of vitamin C standard solution. b. Pour this into a 50 mL Ehrlenmeyer flask (the shape of this flask allows you to swirl the solution to mix it without spilling). c. Add 10 drops of starch indicator solution. d.
Set up the 50 mL buret on the the ringstand. e. Use a funnel to carefully fill the buret with your iodine titration solution. f. Write down the initial volume of the iodine titration solution in the buret. g. Place the Ehrlenmeyer flask (containing the vitamin C and starch solutions) under the buret. h. Carefully release the spring clamp of the buret to add iodine solution drop by drop. i. Swirl the flask to mix in the iodine solution after each addition. j. The titration is complete when the iodine creates a blue-back color in the solution that lasts for longer than 20 seconds. k. Record the final volume of the iodine solution in the buret. . The difference between the initial volume and the final volume is the amount of iodine titration solution needed to oxidize the vitamin C. m. Repeat this step three times. You should get results that agree within about 0. 1 mL. vi. Prepare frozen canned orange juice. vii. If any of the orange juice samples contain pulp, filter them through clean cheesecloth before doing the titration. n. Use a clean 50 mL graduated cylinder to measure 20 mL of the fresh-squeezed juice. o. Pour this into a 50 mL Ehrlenmeyer flask (the shape of this flask allows you to swirl the solution to mix it without spilling). . Add 10 drops of starch indicator solution. q. Set up the 50 mL buret on the the ringstand. r. Fill the buret nearly full with your iodine titration solution. s. Write down the initial volume of the iodine titration solution in the buret. t. Place the Ehrlenmeyer flask (containing the vitamin C and starch solutions) under the buret. u. Carefully release the spring clamp of the buret to add iodine solution drop by drop. v. Swirl the flask to mix in the iodine solution after each addition. w. The titration is complete when the iodine creates a distinct color change in the juice/starch solution.
This color change will be harder to see than with the vitamin C solution, since the juice starts out orange. The color will change from orange to grayish brown when the endpoint is reached. If you continue to add iodine, the color will darken further. You want to note the volume of iodine added when the color first changes. x. Record the final volume of the iodine solution in the buret. y. The difference between the initial volume and the final volume is the amount of iodine titration solution needed to oxidize the vitamin C. z. Repeat this step three times. You should get results that agree within about 0. 1 mL. viii.
For each juice (fresh, premium, or from-concentrate), calculate the average amount of iodine needed to titrate a 20 mL sample. ix. Repeat all steps a total of 3 times in order to ensure accurate information. Pictures Starch Indicator Solution Iodine solution Number of| Drops | Needed to | Change the | Indicator:| Type of Juice:| Trial 1: (mL)| Trial 2: (mL)| Trial 3: (mL)| Average: (mL)| | | | | | | | | | | | | | | | | | | | | | | | | | Type of Juice:| Record Qualitative Data: (Color,etc. )Trial 1:| Record Qualitative Data: (Color,etc. )Trial 2”| Record Qualitative Data: (Color,etc. )Trial 3: | Notes:| | | | | | | | | | | | | | | |
