title: ¹H-NMR study of the impact of high pressure and thermal processing on cell membrane integrity of onions.
abstract: Proton nuclear magnetic resonance (¹H-NMR) relaxometry was used to study the effects of high pressure and thermal processing on membrane permeability and cell compartmentalization, important components of plant tissue texture. High pressure treated onions were subjected to pressure levels from 20 to 200 MPa at 5 min hold time at initial temperatures of 5 and 20 °C. Thermally treated onions were exposed for 30 min at temperatures from 40 to 90 °C. Loss of membrane integrity was clearly shown by changes in transverse relaxation time (T(2)) of water at temperatures of 60 °C and above. Destabilization effects on membranes exposed to high pressure were observed at 200 MPa as indicated by T(2) measurements and cryo-scanning electron microscopy (Cryo-SEM). T(2) relaxation successfully discriminated different degrees of membrane damage based on the T(2) shift of the vacuolar component. Analyses of the average water self-diffusion coefficient indicated less restricted diffusion after membrane rupture occurred in cases of severe thermal treatments. Milder processing treatments yielded lower average diffusion coefficients than the controls. ¹H-NMR proved to be an effective method for quantification of cell membrane damage in onions and allowed for the comparison of different food processes based on their impact on tissue integrity.
authors.affiliation: Dept. Food Science and Technology, Univ. of California, Davis, CA, USA. mariaegonzalez@udec.cl
authors.forename: Maria E
authors.initials: ME
authors.lastname: Gonzalez
authors.forename: Diane M
authors.initials: DM
authors.lastname: Barrett
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McCarthy
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Vergeldt
authors.forename: Edo
authors.initials: E
authors.lastname: Gerkema
authors.forename: Ariette M
authors.initials: AM
authors.lastname: Matser
authors.forename: Henk
authors.initials: H
authors.lastname: Van As
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure*; D002463:Cell Membrane Permeability; D002473:Cell Wall / Q000648:ultrastructure; D055598:Chemical Phenomena; D004058:Diffusion; D005504:Food Analysis / Q000379:methods*; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature / Q000009:adverse effects; D007425:Intracellular Membranes / Q000648:ultrastructure; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D019697:Onions / Q000648:ultrastructure*; D015388:Organelles / Q000648:ultrastructure; D018517:Plant Roots / Q000648:ultrastructure*; D011312:Pressure / Q000009:adverse effects; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water