Public Release: 

Those Days Of Cloudy Wine ­ And Other Drinks ­ May Be Over, According to New Cornell Research

Cornell University

American consumers prefer their favorite cool beverages unclouded, like their weather, while drink makers hanker for a longer shelf life. Thanks to new Cornell research, cloudy wine may be a thing of the past.

"Consumers think that if beverages such as apple juice or beer are cloudy, something is wrong with them," said Karl J. Siebert, Cornell professor of food science at the Agricultural Experiment Station in Geneva. "Sometimes something might be wrong with a cloudy drink, like if a beer has been frozen, it could cloud or there might be a growth of a bad microorganism. But, generally, beverages like apple juice and beer are naturally cloudy."

Siebert and other Cornell researchers have been clarifying beverages for several years to give those drinks a longer consumer shelf life. Scientists presented their research in this area in four talks at the 1996 Institute of Food Technologists' annual conference, June 22-26 in New Orleans:

  • Siebert and Penelope Lynn, research technologist in food science, presented "Assessment of Haze-Active Polyphenols and Haze-Active Proteins in Beer" at the food chemistry protein session June 23.

  • Aurea (Tina) Carrasco, graduate student in food science, and Siebert presented "The Relationships Between Instrumental and Human Visual Perception of Turbidity in Clear and Colored Samples" at the sensory evaluation session June 24.

  • Lynn and Siebert were scheduled to present "Comparison of Adsorbents for Apple Juice Colloidal Stabilization" at the fruit and vegetable product session June 26.

  • Immediately afterward, they also were to present "Assessment of Haze-Active Polyphenols and Haze-Active Proteins in Wine and Grape Juice."

What the researchers are trying to find is how effective adsorbents are in removing haze-causing proteins or polyphenols. Beverage manufacturers have ultrafiltration at their disposal, but it is costly. Proteins and polyphenols bind together, and when each is distributed in a beverage more or less equally, the drink tends to become clouded.

"Manufacturers are looking for less expensive ways to clarify those beverages, and they want to know how stable their own product is before they bottle it. They don't want the problem of cloudiness down the road," Siebert said. "We are trying to see which of the haze-removing products works better."

In beer, wine and fruit juices, the proteins and the polyphenols interact to cloud the beverage. Removing either the protein or the polyphenol -- putting each out of balance -- literally clarifies the situation, and from a marketing view, the product will last longer on the shelf, giving the consumer ample time to buy it. Juice manufacturers and wine makers prefer using bentonite to remove the haze-producing protein. Brewers prefer using silica gel to remove the haze-active protein, because it does not remove the foam-producing proteins, which the manufacturers like.

Leaving the proteins alone, drink and juice makers also could remove the polyphenols, rather than the proteins, by using the adsorbent polyvinylpolypyrrolidone, or PVPP.

For his research, Siebert receives funding from the New York State Apple Research Association; Sunsory Ltd., Osaka, Japan; and from Cornell's Center for Advanced Technology in Biotechnology.

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