Abstract:
The detection of Amadori compounds poorly ab-
sorbing in the UV region is challenging. To cope with this
problem, a simple and effective method using ligand-
exchange and sweeping capillary electrophoresis was first
developed. With this method, Amadori compounds can be
detected by UVat 236 nm without derivatization steps and
separated based on the stable levels of Amadori com-
pound-Cu2+
complexes. Under optimal conditions with
background electrolyte of 50 mmol/L copper sulfate,
pH 3.94, and separation voltage 25 kV, baseline separations
of the following five Amadori compounds, N-(1-deoxy-D-
fructos-1-yl) valine (Fru-Val), N-(1-deoxy-D-fructos-1-yl)
leucine (Fru-Leu), N-(1-deoxy-D-fructos-1-yl) alanine (Fru-
Ala), N-(1-deoxy-D-fructos-1-yl) methionine (Fru-Met),
N-(1-deoxy-D-fructos-1-yl) glutamic acid (Fru-Glu), were
achieved within a 20 min run. The method was applied to
analyze these Amadori compounds in two tomato products.
Fru-Glu could be quantitated sensitively down to 0.706 mg/L
in MS powder (a kind of tomato powder), 0.726 mg/L in MS
liquid (a kind of concentrated tomato juice), and the limit of
quantification for the others ranged from0.792 to 1.084 mg/L.
The most abundant Amadori compound was Fru-Glu
(1057.5 mg/100 g) in MS powder; however, Fru-Met was
rarely detected in MS liquid. The accuracy of the method
was tested by recovery measurement of the spiked samples,
which yielded good results (94.2–106.0 %) with relative stan-
dard deviation lower than 5 %. Simultaneously, the method
was also applied in the analysis of Fru-Glu content during a
tomato puree evaporating concentration process. The first sig-
nificant increase in Fru-Glu content coincided with the incre-
ment rate of soluble solids, which indicated that fast evapora-
tion of water could be a critical step for the formation of
Amadori compounds. These results show that this method is
convenient and reliable for rapid analysis of Amadori com-
pounds in tomato products.
