title: Model studies on acrylamide generation from glucose/asparagine in aqueous glycerol.
abstract: 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.
authors.affiliation: Food Chemistry, Department of Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark.
authors.forename: Rikke Vingborg
authors.initials: RV
authors.lastname: Hedegaard
authors.forename: Henrik
authors.initials: H
authors.lastname: Frandsen
authors.forename: Kit
authors.initials: K
authors.lastname: Granby
authors.forename: Anna
authors.initials: A
authors.lastname: Apostolopoulou
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D020106:Acrylamide / Q000138:chemical synthesis*; D001216:Asparagine / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D005990:Glycerol; D007700:Kinetics; D012996:Solutions; D013816:Thermodynamics; D014867:Water
chemical_list: D012996:Solutions; D014867:Water; D020106:Acrylamide; D001216:Asparagine; D005947:Glucose; D005990:Glycerol