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 breakdownAscorbic 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 enzymes oxidative properties.

Just a little moreIn 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][Vitamin C]decreasetimeoxygenInitial Scientific Model of Vitamin C DepletionAscorbic acid breaks down over time when exposed to oxygen..

AssumptionsInitial 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.

MethodsI acquired four different types of Orange Juice:Pasteurized Juice stored in a tin ContainerWestern Family Orange JuicePasteurized Juice never stored in tinWestern Family Orange JuiceFlash PasteurizedOdwalla Orange Juice Fresh Squeezed (non-pasteurized)California Navel Oranges

ThenI 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

Chart2

131112138

131112138

131113138

131214138

131215148

141316148

151417148

WF (tin)

Odwalla

WF Plastic

Tin

Fresh

Time (days)

Number of Drops of Indophenol

Relative Ascorbic Acid Concentrations in a Variety of Orange Juices

Sheet1

DayWF (tin)OdwallaWF PlasticTinFresh

1131112138

2131112138

3131113138

4131214138

5131215148

6141316148

7151417148

Sheet1

WF (tin)

Odwalla

WF Plastic

Tin

Fresh

Time (days)

# of drops to titrate

Relative Concentration of Ascorbic Acid in a Variety of Orange Juices

Sheet2

WF (tin)

Odwalla

WF Plastic

Tin

Fresh

Time (days)

Number of Drops of Indophenol

Relative Ascorbic Acid Concentrations in a Variety of Orange Juices

Sheet3

Ascorbic Acid LossApproximate indicator drop increase per dayFresh Squeezed JuiceW.F. (tin)W.F. (packaged in tin but stored in plastic)OdwallaW.F. (plastic)

0 drops/day0.14 drops/day0.29 drops/day

0.43 drops/day0.71 drops/day

ConnectionsClaim 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 ContinuedClaim 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]timeheatOxidation ofVitamin CenzymesoxygenOxidation ofTinoxygentin

So that got me wonderingWhat 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?