Influence of sulfur fertilization on the amounts of free amino acids in wheat. correlation with baking properties as well as with 3-aminopropionamide and acrylamide generation during baking.
Sulfur (S) fertilization has been long-known to influence the amounts of total free amino acids in plants. To determine the impact of S deficiency in wheat on the concentration of, in particular, free asparagine, the spring wheat cultivar 'Star' was grown in a laboratory scale (5 L pot) at five different levels of S fertilization. After maturity, the kernels were milled into white flours (1-5) and analyzed for their contents of total S and total nitrogen as well as for free amino acids and glucose, fructose, maltose, and sucrose. Extremely high concentrations of free asparagine (Asn; 3.9-5.7 g/kg) were determined in flours 1 and 2 (30 and 60 mg of S), whereas much lower amounts (0.03-0.4 g/kg) were present in flours grown at higher S levels. The amounts of the reducing carbohydrates were, however, scarcely affected by S fertilization. In agreement with the high amount of Asn in flours 1 and 2, heating of both flours led to the generation of very high amounts of acrylamide (1.7-3.1 mg/kg) as well as of 3-aminopropionamide (40-76 mg/kg). Similar concentrations were measured in crispbread prepared from both flours. Application of rheological measurements on doughs prepared from each flour and a determination of the loaf volume of bread baked therefrom clearly indicated that flours 1 and 2 would be excluded from commercial bread processing due to their poor technological properties. Two commercial flours showed relatively low concentrations of acrylamide after a thermal treatment.
Granvogl
Michael
M
Chair for Food Chemistry, Technical University of Munich, Lichtenbergstrasse 4, D-85748 Garching, Germany.
Wieser
Herbert
H
Koehler
Peter
P
Tucher
Sabine Von
SV
Schieberle
Peter
P
D020106:Acrylamide / Q000032:analysis*; D000596:Amino Acids / Q000032:analysis*; D001939:Bread / Q000032:analysis; D005308:Fertilizers; D005433:Flour / Q000032:analysis; D006358:Hot Temperature; D013455:Sulfur / Q000008:administration & dosage*; D014908:Triticum / Q000737:chemistry* / Q000254:growth & development; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000032:analysis
D000596:Amino Acids; D005308:Fertilizers; D015091:beta-Alanine; D020106:Acrylamide; C012731:beta-alanine amide; D013455:Sulfur