T. Stolle-smits et al., Preheating effects on the textural strength of canned green beans. 1. Cellwall chemistry, J AGR FOOD, 48(11), 2000, pp. 5269-5277
Variable preheating conditions allowed the modification of the firmness of
two green bean cultivars after processing. The aim of this study was to elu
cidate the biochemical basis of this phenomenon and to relate pectin differ
ences to different inherent firmness of two cultivars. The preheating tempe
rature, which resulted in the highest retention of firmness after steriliza
tion, corresponded with the optimal temperature for pectin methylesterase a
ctivity. After this preheating treatment, there was an overall reduction of
the degree of methylation of the cell wall pectin. In addition, the yields
of the buffer and chelator soluble fractions, as well as their average mol
ecular mass, were higher after sterilization. Firmness differences between
the two cultivars seemed to be related to the degree of methylation, the de
gree of acetylation, and the total amount of pectins. Preheating of green b
eans affects texture after sterilization most likely by demethylation of pe
ctin by pectin methylesterase thereby (i) decreasing the beta -eliminative
degradation of pectin and (ii) increasing the capacity of pectin to form Ca
2+-mediated complexes.