title: Effect of partial hydrolysis with an immobilized proteinase on thermal gelation properties of beta-lactoglobulin B.
abstract: We have investigated the influence of partial hydrolysis with an immobilized proteinase from Bacillus licheniformis on the thermal gelation of isolated beta-lactoglobulin B. Gelation behaviour was determined by dynamic rheological measurements (small deformation) and the gels were characterized with respect to microstructure and water-holding properties. A fine-stranded gel with a complex modulus of approximately 2000 Pa was formed from beta-lactoglobulin (50 g/l in 75 mM-Tris-HCl, pH 7.5). Limited hydrolysis prior to thermal gelation resulted in coarser gels with thicker protein strands and larger pores. Gel structure correlated with its permeability, proton mobility and water-holding capacity. Total stiffness gel increased with low degrees of hydrolysis, but decreased after prolonged hydrolysis. Maximal gel stiffness was 1.5-fold that gels made from of unhydrolysed beta-lactoglobulin. This was much lower than the stiffening effect obtained after partial hydrolysis of whey protein isolate, showing that the gel strengthening effect of partial hydrolysis was depedent on the protein composition and/or the hydrolysis and gelatin conditions. A mechanism to explain the observed effects of hydrolysis on gelation and gel properties is presented.
authors.affiliation: Department of Dairy and Food Science, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. jo@kvl.dk
authors.forename: J
authors.initials: J
authors.lastname: Otte
authors.forename: S B
authors.initials: SB
authors.lastname: Lomholt
authors.forename: R
authors.initials: R
authors.lastname: Ipsen
authors.forename: K B
authors.initials: KB
authors.lastname: Qvist
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005782:Gels; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D009682:Magnetic Resonance Spectroscopy; D010539:Permeability; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012212:Rheology; D012697:Serine Endopeptidases / Q000378:metabolism*; D014783:Viscosity
chemical_list: D004800:Enzymes, Immobilized; D005782:Gels; D007782:Lactoglobulins; D012697:Serine Endopeptidases