Which O.J. Should You Buy? How orange juice processing affects the rate of vitamin C loss.

Vitamin C is an organic molecule known as ascorbic acid. Ascorbic acid reacts chemically with indophenol, an indigo indicator, resulting in the bleaching of the dark color. Relative concentration of ascorbic acid is determined by counting the number of drops of solution required for bleaching. Background Information

More breakdown… Ascorbic acid breaks down in the process of oxygen in an oxidation reaction. Enzymes present in citrus fruits increase the rate of oxidation. During juice processing, loss of A.A. potency due to enzymes is minimal because: –A deaeration step minimizes amount of oxygen. –High pasteurization temperatures readily destroy the enzyme’s oxidative properties.

Just a little more… In flash pasteurization, juices are heated briefly and then rapidly cooled. Vitamin C is a sensitive molecule that is altered in the presence of heat. Tin competes with ascorbic acid for oxygen and tin is preferentially oxidized.

[Vitamin C] decrease time oxygen Initial Scientific Model of Vitamin C Depletion Ascorbic acid breaks down over time when exposed to oxygen..

Assumptions Initial differences in ascorbic acid concentration in juice did not affect the rate of breakdown. Storing juice in plastic containers would remove the container variable on rate of ascorbic acid depletion. Flash pasteurized juices are exposed to less heat than juices which experience standard pasteurization. All juices tested did not have fructose added: –Ascorbic acid reacts with carbonyl group of fructose to decrease ascorbic acid concentration.

Methods I acquired four different types of Orange Juice: –Pasteurized Juice stored in a tin Container »Western Family Orange Juice –Pasteurized Juice never stored in tin »Western Family Orange Juice –Flash Pasteurized »Odwalla Orange Juice –Fresh Squeezed (non-pasteurized) »California Navel Oranges

Then… I collected juice from 6 California Navel oranges and stored it in a plastic juice bottle. I stored some orange juice from a tin can in a plastic juice bottle – the remaining juice was left in the tin container for additional testing.

Finally… I used a 60 mg/L solution of indophenol. Set up two equal vials of water and indicator (10 ml). Titrated O.J. to solutions using an eye-dropper until colors were the same. Recorded the number of drops.

Results

Ascorbic Acid Loss… Approximate indicator drop increase per day Fresh Squeezed Juice W.F. (tin) W.F. (packaged in tin but stored in plastic) Odwalla W.F. (plastic) 0 drops/day 0.14 drops/day 0.29 drops/day 0.43 drops/day 0.71 drops/day

Connections… Claim 1: Juice exposed to tin will lose ascorbic acid at a slower rate than juice not exposed to tin. Support: According to the data table, all pasteurized juice that had been exposed to tin lost ascorbic acid at a slower rate. Of the juice originally packaged in tin, the juice stored in tin lost ascorbic acid more slowly. Refute: Fresh juice did not loose ascorbic acid, and therefore was better at retaining ascorbic acid than juice exposed to tin.

Connections Continued… Claim 2: Juices exposed to higher temperatures will loose ascorbic acid more gradually than juices exposed to less heat due to the inactivation of enzymes that degrade ascorbic acid. Refute: When comparing juices never stored in tin, ascorbic acid loss was inversely proportional to heat time exposure: the greater the heat, the more rapid the loss.

Revised Model [Vitamin C] Decreased [Vitamin C] time heat Oxidation of Vitamin C enzymes oxygen Oxidation of Tin oxygen tin

So that got me wondering… What would happen if the juice containers were not capped, but rather exposed to the oxygen of the refrigerator? What would happen if fructose was added to the fresh squeezed juice?