title: Effect of gel firmness at cutting time, pH, and temperature on rennet coagulation and syneresis: an in situ 1H NMR relaxation study.
abstract: The objective of this study was to monitor rennet-induced milk gel formation and mechanically induced gel syneresis in situ by low-field NMR. pH, temperature, and gel firmness at cutting time were varied in a factorial design. The new curve-fitting method Doubleslicing revealed that during coagulation two proton populations with distinct transverse relaxation times (T2,1=181, T2,2=465 ms) were present in fractions (f1=98.9%, f2=1.1%). Mechanical cutting of the gel in the NMR tube induced macrosyneresis, which led to the appearance of an additional proton population (T2,3=1500-2200 ms) identified as whey. On the basis of NMR quantification of whey water the syneresis rate was calculated and found to be significantly dependent on pH and temperature.
authors.affiliation: Quality and Technology Group, Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark. chha@life.ku.dk
authors.forename: Christian Lyndgaard
authors.initials: CL
authors.lastname: Hansen
authors.forename: Asmund
authors.initials: A
authors.lastname: Rinnan
authors.forename: Søren Balling
authors.initials: SB
authors.lastname: Engelsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Janhøj
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Micklander
authors.forename: Ulf
authors.initials: U
authors.lastname: Andersen
authors.forename: Frans
authors.initials: F
authors.lastname: van den Berg
mesh_terms: D000818:Animals; D002417:Cattle; D012085:Chymosin / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
chemical_list: D005782:Gels; C025350:rennet; D012085:Chymosin