Those days of cloudy wine -- and other drinks -- may be over,
By Blaine Friedlander
NEW ORLEANS -- American consumers prefer their favorite cool beverages unclouded, like their weather, while drink makers hanker for a long shelf life. Thanks to new Cornell University 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 it," said Karl J. Siebert, Cornell professor of food science at the Agriculture Experiment Station in Geneva, N.Y. "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 will present 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, Cornell research technologist in food science, will present "Assessment of Haze-Active Polyphenols and haze-active proteins in beer," at the food chemistry protein session, Sunday, June 23, at 9:35 a.m.
- Aurea (Tina) Carrasco, Cornell graduate student in food science, and Siebert will present "The relationships between instrumental and human visual perception of turbidity in clear and colored samples," at the sensory evaluation session, Monday, June 24, at 3:20 p.m.
- Lynn and Siebert will present "Comparison of adsorbents for apple juice colloidal stabilization," at the fruit and vegetable product session, June 26, at 11:05 a.m.
- Immediately afterward, they will present, "Assessment of haze-active polyphenols and haze-active proteins in wine and grape juice," at the same session, at 11:20 a.m.
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 could also remove the polyphenols, rather than the proteins by using the adsorbent polyvinylpolypyrrolidone, or PVPP. This, too, would knock off protein-polyphenol proportion out of kilter, reduce the haze and presents clarity.
For his research, Siebert receives funding from the New York State Apple Research Association; Sunsory, Ltd., Osaka, Japan; and from Cornell's Center in Advanced Technology in Biotechnology.
In the June 24 presentation by Carrasco and Siebert, the researchers will explain how consumers relate to beverage haze. They have found that consumers see more haze than previously thought. Consumers saw more haze in clear or yellow beverages, and saw less haze in drinks that were dark red.
The scientists also began to define the visual perception of haze by obtaining a dose-response curve to the human perception. Also, a descriptive analysis panel was conducted to look at beverage samples, rate the different responses onto scales and to learn about how humans perceive haze.