Ten-Year Study of Orange and Grapefruit Juice Yields Verdict on Vitamin C

Frozen concentrated orange juice generally has the highest vitamin C levels compared to other commercial orange and grapefruit juice products, but even if you favor one of the others, you're probably still getting your daily requirement of the vitamin. That's according to a new, ten-year study reported in the July 16 issue of the American Chemical Society's Journal of Agricultural and Food Chemistry. The American Chemical Society is the world's largest scientific society.

Scientists looked at the vitamin C levels of 2299 samples of orange and grapefruit juice products collected from 21 Florida processors between February 1986 and October 1995. They found that 95.7% of the 2299 samples qualified to provide more than 100% of the daily value (DV) of vitamin C determined by the FDA. Overall, one 8-ounce serving of frozen concentrated orange juice had the highest vitamin C content (173% DV), with orange juice from concentrate coming in second (161.2% DV) and pasteurized orange juice in third (138.4% DV).

Grapefruit juice had generally lower levels of vitamin C than orange juice. Slightly higher levels of vitamin C were found in grapefruit juice from concentrate compared to pasteurized grapefruit juice.

The study was conducted by Dr. Hyoung S. Lee and Mr. Gary A. Coates of the Florida Department of Citrus in Lake Alfred, Fla. "Frozen concentrated orange juice and orange juice from concentrate can be blended to produce juice products with relatively uniform vitamin C content throughout the season," said Lee. "However, pasteurized orange juice is processed based on fruit availability at the time, and this could reflect the natural variability of vitamin C throughout the growing season for the fruit." Pasteurized orange juice showed higher levels of vitamin C during the months of December through March, when vitamin C-rich Hamlin oranges were a major contributor to the orange juice market. Samples collected between May and July generally had lower values of vitamin C. "This probably reflected the use of larger amounts of Valencia oranges which have lower amounts of vitamin C of the three major Florida sweet oranges," said Lee.

The Florida citrus industry accounts for nearly three-fourths of all U.S. citrus products. Lee and his colleagues hope that the study will provide a guide for values and ranges of vitamin C in commercially processed juices from Florida and assist with the nutrition labeling of these products. Much of the data that existed on the nutrient content of Florida citrus products prior to this study had been collected more than 20 years ago and did not take into account more recent changes in the industry. These include tree changes due to major freezes in Florida during the 1980's, increased blending practices with foreign orange juices (mainly from Brazil), and market changes such as plant closures and mergers.

During the course of the study, the number of plants which provided concentrate samples decreased, whereas the number of plants for pasteurized orange juice increased. "This was due to a trend of increasing sales of pasteurized juice, resulting from consumer's perception of improved convenience and 'fresher' quality when compared to concentrate products," said Lee.

Since juice samples were taken at the point of manufacture rather than from grocery stores, the current study did not take into account any changes in vitamin C levels that could have occurred during marketing. Vitamin C retention will also vary depending on the length of storage time and the type of container in which a product is stored. According to Lee, the second phase of this study will look at vitamin C levels in retail citrus juice products collected from markets throughout the U.S.

This work was funded by the citrus growers of Florida.

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Theresa Laranang-Mutlu

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