Effect of gel firmness at cutting time, pH, and temperature on rennet coagulation and syneresis: an in situ 1H NMR relaxation study.
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.
Hansen
Christian Lyndgaard
CL
Quality and Technology Group, Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark. chha@life.ku.dk
Rinnan
Asmund
A
Engelsen
Søren Balling
SB
Janhøj
Thomas
T
Micklander
Elisabeth
E
Andersen
Ulf
U
van den Berg
Frans
F
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
D005782:Gels; C025350:rennet; D012085:Chymosin