Model studies on acrylamide generation from glucose/asparagine in aqueous glycerol.
Acrylamide formation from asparagine and glucose in different ratios in neutral glycerol/water mixtures was found to increase with decreasing water activity (0.33 < or = aw < or = 0.71 investigated) and increasing temperature (120 degrees C < or = T < or = 160 degrees C investigated). The initial rate of acrylamide formation was found to be approximately proportional to the asparagine concentration for an excess of asparagine, but less dependent on an excess of glucose. A steady-state concentration of acrylamide was established at 160 degrees C after 1 h for aw = 0.33 (30 microg x L-1 for GLU:ASN = 10:1, 11 microg x L-1 for GLU:ASN = 1:1, and 130 microg x L-1 for GLU:ASN = 1:10) and for aw = 0.47 (15 microg x L-1 for GLU:ASN = 10:1 and 80 microg x L-1 for GLU:ASN = 1:10), suggesting a protection by glucose against acrylamide degradation. The energy of activation, as estimated from the temperature dependence of the initial rate, increased with decreasing aw despite a higher rate of formation of acrylamide at low aw. For high aw, water elimination from a reaction intermediate is suggested to be rate determining. For low aw, the increase in energy of activation (and enthalpy of activation) is accordingly counteracted by a more positive entropy of activation, in agreement with decarboxylation as rate determining at low aw.
Hedegaard
Rikke Vingborg
RV
Food Chemistry, Department of Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
Frandsen
Henrik
H
Granby
Kit
K
Apostolopoulou
Anna
A
Skibsted
Leif H
LH
D020106:Acrylamide / Q000138:chemical synthesis*; D001216:Asparagine / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D005990:Glycerol; D007700:Kinetics; D012996:Solutions; D013816:Thermodynamics; D014867:Water
D012996:Solutions; D014867:Water; D020106:Acrylamide; D001216:Asparagine; D005947:Glucose; D005990:Glycerol