Dynamic Surface Properties of the Proteose-Peptone Fraction of Bovine Milk

¹ Dipartimento de Scienze degli Alimenti, Universitàdegli studi di Udine, via Marangoni 97, 33100 Udine, Italy
² Unité de Technologie des Industries Agro-Alimentaires, Faculté Universitaire des Sciences Agronomiques, 2 Passage des Déportes, 5030 Gembloux, Belgium

Proteose-peptone is a heat-stable and acid-soluble protein fraction of milk that has important functional properties. Component 3, which is the most hydrophobic fraction, appears to be largely responsible for the physicochemical properties of proteose-peptones and for their important biological role in milk. In this study, total proteose-peptone was prepared from bulk skim milk by precipitation with ammonium sulfate, and the hydrophobic fraction was purified by FPLC® (Pharmacia Fine Chemicals, Uppsala, Sweden). The drop volume method was used to investigate the dynamic surface activity of total proteose-peptone and component 3 of proteose-peptone at the air-water interface and at the oil-water interface. In general, proteose-peptones are good surfactants at both interfaces. Of all proteose-peptones, component 3 causes a more rapid reduction of interfacial tension in both interfaces. A system for measuring film balance was used to obtain more information about the surface and mechanical properties of proteose-peptone monolayers. We deduced from the compression isotherms that component 3 of proteose-peptone and total proteose-peptone films spread at the air-water interface present different mechanical properties.

Key Words: dynamic surface tension • proteose-peptone • component 3

Submitted on October 6, 1997
Accepted on March 23, 1998