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Effect of Cooking and Pre‐Cooking on Cell‐Wall Chemistry in Relation to Firmness of Carrot Tissues
Author(s) -
Ng Annie,
Waldron Keith W
Publication year - 1997
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199704)73:4<503::aid-jsfa762>3.0.co;2-z
Subject(s) - chemistry , polysaccharide , food science , cell wall , daucus carota , softening , residue (chemistry) , polymer , biochemistry , organic chemistry , botany , biology , statistics , mathematics
The aim of this work was to investigate heat‐induced changes in cell wall polysaccharides of carrot in relation to texture. Discs of fresh carrot ( Daucus carota cv Amstrong) tissue were subjected to cooking (100°C, 20 min), with or without a pre‐cooking treatment (50°C, 30 min). Alcohol‐insoluble residues were prepared from the tissues and were extracted sequentially with water, NaCl, CDTA, Na 2 CO 3 and 0·5 M KOH to leave a residue. These were analysed for their carbohydrate compositions, their degree of methyl esterification and the molecular size of selected soluble polysaccharides. Cooking caused tissues to soften. This involved cell separation, an increase in water‐ and salt‐soluble, high‐molecular‐weight pectic polysaccharides and a concomitant decrease in the pectic polymers in all wall extracts and the residue. Pre‐cooking prior to cooking enhanced cell–cell adhesion and reduced the extent of softening. This was accompanied by a general reduction in the degree of methylesterification of cell‐wall pectic polymers, and a decrease in the cooking‐induced modification to all pectic fractions. The firming effect of pre‐cooking could be reversed by extracting the precooked+cooked tissue with CDTA, a chelating agent. The role of Ca 2+ cross‐linked polymers and pre‐cooking in the enhancement of firmness are discussed. © 1997 SCI.