title: Optimised formation of blue Maillard reaction products of xylose and glycine model systems and associated antioxidant activity.
abstract: BACKGROUND
  A blue colour can be formed in the xylose (Xyl) and glycine (Gly) Maillard reaction (MR) model system. However, there are fewer studies on the reaction conditions for the blue Maillard reaction products (MRPs). The objective of this study is to investigate characteristic colour formation and antioxidant activities in four different MR model systems and to determine the optimum reaction conditions for the blue colour formation in a Xyl-Gly MR model system, using the random centroid optimisation program.
  
  
  RESULTS
  The blue colour with an absorbance peak at 630 nm appeared before browning in the Xyl-Gly MR model system, while no blue colour formation but only browning was observed in the xylose-alanine, xylose-aspartic acid and glucose-glycine MR model systems. The Xyl-Gly MR model system also showed higher antioxidant activity than the other three model systems. The optimum conditions for blue colour formation were as follows: xylose and glycine ratio 1:0.16 (M:M), 0.20 mol L⁻¹ NaHCO₃, 406.1 mL L⁻¹ ethanol, initial pH 8.63, 33.7°C for 22.06 h, which gave a much brighter blue colour and a higher peak at 630 nm.
  
  
  CONCLUSIONS
  A characteristic blue colour could be formed in the Xyl-Gly MR model system and the optimum conditions for the blue colour formation were proposed and confirmed.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P.R. China.
authors.forename: Zi
authors.initials: Z
authors.lastname: Yin
authors.forename: Qian
authors.initials: Q
authors.lastname: Sun
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Jing
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives / Q000737:chemistry; D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry*; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D003116:Color; D000431:Ethanol / Q000737:chemistry; D005505:Food Coloring Agents / Q000138:chemical synthesis / Q000737:chemistry*; D005527:Food, Fortified / Q000032:analysis; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015416:Maillard Reaction; D008956:Models, Chemical; D012984:Software; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry; D013223:Statistics as Topic; D014994:Xylose / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D000975:Antioxidants; D005505:Food Coloring Agents; D012997:Solvents; D001224:Aspartic Acid; D000431:Ethanol; D014994:Xylose; D000409:Alanine; D005998:Glycine
keywords: Maillard reaction; antioxidant activity; blue colour; random centroid optimisation