Hydrolyzed whey inhibits culture agglutination.

Culture agglutination is a problem that often occurs during the production of cottage cheese. When milk is fermented, culture agglutination takes place when lactic acid-producing bacteria bind with immunoglobulins present in milk and form extended chains of cells that clump together and cause localized acid production.

Acid produced by these aggregated cells causes casein to precipitate or coagulate around the culture. Thus, localized acid production enhances the mass of culture aggregates to the degree that most aggregates fall to the bottom of the cheese vat and form a layer of sludge and acid that's distributed unevenly throughout the skim milk. A large top-bottom differential of pH and solids in the vat appears when culture agglutination occurs.

Researchers at the University of Kentucky believed it might be possible to inhibit culture agglutination. This might be done by hydrolyzing immunoglobulins in whey and using the binding components or fragments to block intact immune proteins from binding to the antigenic site on the culture cell's surface.

They prepared peptide fragments from whey with papain and harvested the peptides from a 10,000 molecular weight cutoff (MWCO) ultrafiltration membrane. The papain was used to hydrolyze sweet whey. Researchers added buffer salts to whey peptides to prepare media that were tested for their ability to inhibit culture agglutination.

The scientists inoculated skim milk with Lactococcus lactis spp. lactis B62 or E72. They determined culture agglutination by measuring upper-center and bottom pH values of the skim milk while it was in graduated cylinders for 5 hours. A pH differential was calculated by subtracting the bottom pH from the upper-center pH.

Cultures grown in media containing whey peptides agglutinated in skim milk to a lesser degree than when they grew in the control medium. Culture agglutination was inhibited to a greater degree when cultures grew in a 1000 MWCO peptide medium than when they grew in the 10,000 MWCO peptide medium or the 3000 MWCO peptide medium. When culture E72 grew in media containing 1000 MWCO peptides, culture agglutination was completely inhibited.

Further information. Clair Hicks, Department of Animal Sciences, University of Kentucky, 410 W.P. Garrigus Building, Lexington, KY 40546; phone: [phone]; fax: [phone]; email: [e-mail].