Structural characterisation of pectin obtained from cacao pod husk. Comparison of conventional and subcritical water extraction

Pectin was obtained with citric acid and subcritical water extraction from cacao pod husk with or without a previous step consisting of a supercritical fluid extraction of phenols. By subcritical conditions a higher yield (10.9%) was attained in a time 3-fold shorter than that obtained by conventional extraction (˜8%) and a greater effectiveness in the recovery of pectin with higher molecular weight (750 kDa) was also found. Regarding pectin structure, galacturonic acid and degree of methyl esterification content were similar (˜55 and ˜36%, respectively) in both methods. Moreover, pectin recovered by citric acid presented 2-fold higher amount of impurities as compared to subcritical water extraction. Hardly any effects of a previous supercritical treatment were observed in the structure and composition of pectin, indicating the efficiency of the integrated supercritical carbon dioxide and subcritical water extraction as green processes for the obtainment of phenol and pectin from cacao pod husk.This work has been funded by MINECO of Spain, Projects AGL2014-53445- R and AGL2017-89417-R.N. Muñoz-Almagro thanks to Ministry of Economy of Spain for providing her FPI predoctoral fellowship. L. Valadez-Carmona is grateful to Consejo Nacional de Ciencia y Tecnología (CONACyT) for the fellowship grant number 254415 and IPN for the financial support to accomplishment of research internship in Institute of Food Science Research (CSIC-UAM).Peer reviewe