title: Firming of fruit tissues by vacuum-infusion of pectin methylesterase: Visualisation of enzyme action.
abstract: Apple pieces were vacuum-impregnated with either a pectin methylesterase (PME) and calcium solution or with water prior to pasteurization. Pasteurized apple pieces impregnated with PME and calcium showed a significantly higher firmness. Moreover, solid state (13)C NMR spectroscopy of apple cell wall residues revealed an increase of their molecular rigidity. Exogenous PME addition involved a decrease from 82% to 45% of apple pectin degree of methyl-esterification. Microscopic observations of apple slices immunolabelled with antibodies specific for pectins showed that (i) demethyl-esterification was more intense in the cell wall region lining intercellular spaces (demonstrating a key role for these intercellular channels in the enzyme penetration in the tissue during vacuum-infusion) and that (ii) the number of calcium-dimerized deesterified homogalacturonan chains increased. The results corroborate the hypothesis that vacuum-impregnated PME action liberates free carboxyl groups along pectin chains that could interact with calcium, increasing the rigidity of pectins and finally the mechanical rigidity of apple tissue.
authors.affiliation: Université Lyon 1, Laboratoire de Recherche en Génie Industriel Alimentaire (EA 3733), IUT A -- Département de Génie Biologique, Technopole Alimentec -- rue Henri de Boissieu, 01060 Bourg en Bresse Cedex 9, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Guillemin
authors.affiliation: UR1268 Biopolymères Interactions Assemblages, INRA, 44300 Nantes, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Guillon
authors.affiliation: Université Lyon 1, Laboratoire de Recherche en Génie Industriel Alimentaire (EA 3733), IUT A -- Département de Génie Biologique, Technopole Alimentec -- rue Henri de Boissieu, 01060 Bourg en Bresse Cedex 9, France. Electronic address: degraeve@iutbourg.uni-lyon1.fr.
authors.forename: Pascal
authors.initials: P
authors.lastname: Degraeve
authors.affiliation: UR1268 Biopolymères Interactions Assemblages, INRA, 44300 Nantes, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Rondeau
authors.affiliation: UR1268 Biopolymères Interactions Assemblages, INRA, 44300 Nantes, France.
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Devaux
authors.affiliation: Laboratoire d'Etudes et de Recherches sur le Matériau Bois, UMR 1093 INRA-AgroParisTech-Université Nancy I, 54042 Nancy, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Huber
authors.affiliation: Laboratoire d'Etudes et de Recherches sur le Matériau Bois, UMR 1093 INRA-AgroParisTech-Université Nancy I, 54042 Nancy, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Badel
authors.affiliation: Université de Bourgogne, Equipe Eau -- Molécules actives -- Macromolécules -- Activités (EA 581), ENSBANA, 1 Esplanade Erasme, 21000 Dijon, France.
authors.forename: Rémi
authors.initials: R
authors.lastname: Saurel
authors.affiliation: UR1268 Biopolymères Interactions Assemblages, INRA, 44300 Nantes, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Lahaye
keywords: Fruit firmness; Pectin; Pectin methylesterase; Vacuum-impregnation