Improvement in the measurement of spectrophotometric data in the m-hydroxydiphenyl pectin determination methods

in the pectin analysis of foods by visible spectrophotometry using the m-hydroxydiphenyl (MHDP) as the chromogenic reagent, the evolution of the absorbance at 520 nm of the MHDP/5FF chromophore with respect to the elapsed time from the beginning of the reaction for different D-galacturonic acid concentrations was studied. It was observed that after 45 min, the stability of the readings predicted by the different methods was not reached. This evolution depended on the D-galacturonic acid concentration. The need to analyse the samples in sequence was noted, in such a way that after the addition of MHDP, a protocol was established so that the spectrophotometric data measurements taken at the highest absorbance have high reproducibility. (c) 2005 Elsevier Ltd. All rights reserved.