Engineering OJ: Terrible Smells Make Juice Fresh
Credit: USDA
Credit: USDA

Ah, freshly-squeezed orange juice - what makes it taste so good? Is it that hidden smell of paint thinner? Or perhaps the subtle hint of mothballs?

Researchers have isolated more than 40 of the natural compounds that make up the aroma of orange juice. When smelling the extracted compounds, volunteers compared some of the scents to gasoline, cut-grass, roses, cheesy feet, and cotton candy.

"By themselves some of them stink, but they are necessary to the mix," said Anne Plotto, from the Agriculture Research Service of the U.S. Department of Agriculture.

Plotto gave the analogy of adding a pinch of salt in a recipe for a sweet dessert. In small amounts, unexpected ingredients enhance overall flavor.

The scientists study the chemical composition of OJ in such detail because the aroma compounds generally evaporate away when the juice is concentrated for storage and transportation purposes. So juice companies buy "flavor packs," which are added to the concentrate when it is reconstituted with water. These packs contain the missing compounds in various concentrations.

"The goal is to capture the freshly-squeezed taste," Plotto told LiveScience in a telephone interview. Her research is intended to help U.S. orange juice companies compete in the global market. In Florida alone, citrus-production is an $8 billion a year industry.

To improve the flavor packs, Plotto and her colleagues are evaluating how much of a certain compound is needed for a person to detect it.

"If you put too much [of one compound], it won't be good," Plotto said. Determining the minimum amount needed could help avoid this.

In multiple tests, volunteers smelled and tasted various concoctions. Aromas can affect the taste not only through the nose, but also by wafting up the back of the throat during swallowing. Different compounds can interact with each other in a way that enhances or suppresses their aroma.

There may also be an interaction with the non-volatile substances - like sugars, acids and pulp - that do not evaporate away during condensation. Without any added aromas, this "deodorized" juice has a sweet, acidic taste, according to Plotto - who has had to sample it many times in setting up the taste-tests.

"It's not bad," she said.