Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume 45,
Number 3, March 2007, pp.120-125
Monitoring by Liquid Chromatography Coupled to
Mass Spectrometry the Impact of pH and Temperature on the Pigment
Pattern of Cactus Pear Fruit Extracts
José A. Fernández-López[1],
Rosario Castellar[1], José M. Obón[1], and Luis
Almela[2]
[1]Department of Chemical Engineering, Polytechnic University
of Cartagena, Paseo Alfonso XIII 52, E-30203 Cartagena (Murcia),
Spain and
[2]Department of Agricultural Chemistry, University of Murcia,
E-30071 Murcia, Spain
The influence of pH and moderate heating (50°C)
on the color and individual betacyanin content of pigment extracts
from cactus pear fruits (Opuntia stricta) is studied in the course
of this paper. The study is carried out by using a high-performance
liquid chromatograph equipped with a photodiode array detector
and coupled to a mass spectrometer. The results point to a pH-dependent
degradation mechanism, which is reflected in the chromatographic
patterns obtained at different exposure times (0–28 h).
At pH 3, 15-descarboxy-betanin is the most resistant betacyanin
derivative. At pH 5, seven peaks are detected after 8 h, the most
prominent being betanin, cyclo-dopa-5-O-b-glucoside, and betalamic.
In the assay conducted at pH 7, rapid color loss affects all the
pigments, except for betanin.
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