Even after normal filtration, higher amounts of phenolic compounds--when oxidized--can cause turbidity, discoloration and astringent bitterness in beverages in prolonged storage. The catechin and procyanidin of the polyphenols group reacts with protein to cause turbidity, reducing a beverage's shelflife. In wines, oxidation results in a flat, less aromatic product.

“Consumers often expect a beverage that is clear and brilliant. From their perspective, turbidity is associated with an old, oxidized beverage that has exceeded its shelflife,” says Jason Asche, a product manager for BASF (Florham Park, N.J.). Without changing the sensory aspects of the drink, BASF's Divergan[r]--an interlinked, insoluble, Polyvinylpolypyrrolidone (PVPP) produced by popcorn polymerization--will remove polyphenols and proteins.

PVPP is insoluble in acids, bases and organic solvents. Divergan can be added to the beverage to be treated either directly in a powder form or as a suspension. The PVPP swells and increases the active adsorption area by expanding the inner pore diameter. The suspension is stirred repeatedly over the average 30-minute contact time.

Longer contact times also are possible without any negative effect on the wine. Stirring keeps the particles in suspension better and increases the surface area. In cold water, PVPP needs to swell before it can be used, typically one to two hours. In hot water, the PVPP is immediately ready for use. Once Divergan is loaded and forms sediment, it is completely separated from the beer or other beverage in which it is used during filtration, and does not need to be declared on the label.

Divergan works well with other standard stabilizers like silica gel (which is used beforehand to further reduce protein) and Kieselguhr filtration (which removes remaining yeast cells, bacteria and settled haze compounds).

Divergan can be used preventively and remedially. A better catechin adsorption is evident with smaller particle sizes such as those found with Divergan F, which has an average particle size of 40mm. Divergan F is a single-use material, whereas Divergan RS can be reused. The average particle size of Divergan RS is approximately 80-100mm. “Both products are very cost efficient and highly mechanically stable when used as recommended,” says Gero Spika, head of global business management, beverage processing polymers for BASF.

Both Divergan types have a small swelling volume of less than 6L/kg, which with Divergan F has advantages in the filtration run time. Compared with Divergan F, the regenerable Divergan RS works to remove larger particle sizes, is coarser-grained and is mechanically stronger. “These properties ensure that it can be used again and again without causing blockages or other problems,” Spika points out. Divergan F has a lower dosage rate compared to Divergan RS, which is used in a PVPP filter. Divergan RS is the only PVPP that can be used in regenerable PVPP filter lines.

Divergan is highly selective because it specifically reduces the content of active anthocyanogens that cause turbidity. Depending on the wine, beer or juice composition, the addition of Divergan can extend shelflife by six to 12 months, says Asche.

For more information: BASF, Jason Asche, 973-245-6379, www.basf.com/usa