title: Recovery and upgrading bovine rumen protein by extrusion: effect of lipid content on protein disulphide cross-linking, solubility and molecular weight.
abstract: Bovine rumen protein with two levels of residual lipids (1.9% or 3.8%) was subjected to thermoplastic extrusion under different temperatures and moisture contents. Protein solubility in different buffers, disulphide cross-linking and molecular weight distribution were determined on the extrudates. After extrusion, samples with 1.9% residual lipids content had a higher concentration of protein insoluble by undetermined forces, irrespective of feed moisture and processing temperature used. Lipid content of 3.8% in the feed material resulted in more protein participating in the extrudate network through non-covalent interactions (hydrophobic and electrostatic) and disulphide bonds. A small dependency of the extrusion process on moisture and temperature and a marked dependency on lipid content, especially phospholipid, was observed, Electrophoresis under non-reducing conditions showed that protein extrusion with low feed moisture promoted high molecular breakdown inside the barrel, probably due to intense shear force, and further protein aggregation at the die end.
authors.affiliation: Laboratório de Bioquímica e Propriedades Funcionais dos Alimentos, Faculdade de Saúde Pública da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: L C M A
authors.initials: LC
authors.lastname: Vaz
authors.forename: J A G
authors.initials: JA
authors.lastname: Arêas
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002021:Buffers; D002417:Cattle; D004041:Dietary Fats / Q000032:analysis* / Q000302:isolation & purification; D004044:Dietary Proteins / Q000032:analysis* / Q000302:isolation & purification*; D004220:Disulfides / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D007220:Industrial Waste / Q000032:analysis / Q000191:economics; D008055:Lipids / Q000032:analysis*; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D010743:Phospholipids / Q000032:analysis / Q000302:isolation & purification; D012417:Rumen / Q000737:chemistry*; D012995:Solubility; D013440:Sulfides / Q000032:analysis; D014867:Water / Q000032:analysis
chemical_list: D002021:Buffers; D004041:Dietary Fats; D004044:Dietary Proteins; D004220:Disulfides; D007220:Industrial Waste; D008055:Lipids; D010446:Peptide Fragments; D010743:Phospholipids; D013440:Sulfides; D014867:Water