Make condensed orange juice taste fresh.

Flavor is one of the most important qualities of orange juice. Aroma compounds are extensively responsible for the fresh-squeezed taste that consumers prefer. But the compounds evaporate during the condensing process used to make frozen concentrated orange juice. The aroma compounds--blended into mixtures--are sold to juice processors as flavor packs and are added back into the juice along with water before the juice is on the market.

At the USDA-ARS, researchers are gathering information about the thresholds of flavor-impact aroma compounds that make fresh orange juice taste so good. A threshold is the minimum level at which a compound can be detected by smell or taste. To improve juice flavor, it is necessary to unravel the interactions between all the compounds in juice. In addition to flavor compounds, juice contains sugars, acids, pulp, pectin, salts and phenolic compounds that can influence perception of flavor.

To understand the interactions among the compounds and how they affect flavor perception, researchers identified odor and taste thresholds of compounds considered to be important contributors to the product's flavor. They mixed the compounds into deodorized juice rather than water. The team solicited the help of some 50 nonprofessional taste testers.

Each volunteer received 15 samples of chilled orange juice, distributed in five rows of three cups. In each row, two cups contained deodorized juice, and one cup contained juice spiked with a particular unidentified aroma compound. Each row differed in taste and odor intensity, with the top row containing the least amount of the compound and the bottom row the most.

For each row, the volunteers had to smell the cups, guess which one was spiked with a compound and describe the smell. Then, they had to sip through the rows and do the same for taste. Responses differed greatly. Various compounds were described as smelling or tasting like paint thinner, fruit, mothballs and even gasoline.

The orange juice matrix created by the researchers contains more than 40 detectable compounds. Terpenes, alcohols, esters and aldehydes are the most valuable when determining the best tasting juice. Aldehydes and esters are the "top-note" compounds, while terpenes provide the background. Now the juice scientists are trying to find out what relative amounts of these types of compounds are needed to get that fresh-squeezed taste into reconstituted orange juice. Developing flavor packs that more closely mimic fresh juice flavor would improve the desirability of processed orange juice.

Further information. Elizabeth Baldwin, USDA-ARS Citrus and Subtropical Products Laboratory, 600 Avenue S., NW, Winter Haven, FL 33881; phone [phone]; fax: [phone]; email: [e-mail].