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119. High pressure and heat: Effects on onion cell membrane permeability and implications for tissue texture
340
Abstracts / Cryobiology 57 (2008) 315–340
119. High pressure and heat: Effects on onion cell membrane permeability and implications for tissue texture. Maria E. Gonzalez a, Frank Vergeldt b, Henk Van As b, Judy Jernstedt c, Michael J. McCarthy a, Diane M. Barrett a, a Dept. Food Science & Technology, University of California, Davis, CA, USA, b Lab. Biophysics, Wageningen University, Wageningen, The Netherlands, c Dept. of Plant Sciences, University of California, Davis, CA, USA High pressure and thermal treatments induce changes in membrane permeability which, above a threshold of high pressure and temperature, cause loss of cell compartmentation and texture modification. In the present study, integrity of onion cells before and after treatment was assessed by different methods. To obtain information on membrane permeability and cell compartmentalization, 1H-NMR T2 relaxation, conductivity measurements, enzymatic analysis (alliinase) and cell viability determi-
nation after neutral red staining of cell vacuoles were used. Texture analysis of samples was carried out with a TA.XT2 texture analyzer. High pressure treatments consisted of 5 minute holding times at 50, 100, 200, 300 or 600 MPa. Thermal treatments consisted of 30 minute water bath exposure to 40, 50, 60, 70 or 90 °C. All treatments were compared to raw onions. Membrane rupture could clearly be identified at 300 MPa and above in high pressure treatments and at 60 °C and above in thermal treatments. Membrane destabilization effects could already be visualized at 200 MPa and 50 °C treatments. The data suggests that the texture of onions is influenced by the state of the membranes and is abruptly modified once membrane integrity is lost. (Conflicts of interest: None declared. Source of funding: None declared.) doi:10.1016/j.cryobiol.2008.10.120
Abstracts / Cryobiology 57 (2008) 315–340
119. High pressure and heat: Effects on onion cell membrane permeability and implications for tissue texture. Maria E. Gonzalez a, Frank Vergeldt b, Henk Van As b, Judy Jernstedt c, Michael J. McCarthy a, Diane M. Barrett a, a Dept. Food Science & Technology, University of California, Davis, CA, USA, b Lab. Biophysics, Wageningen University, Wageningen, The Netherlands, c Dept. of Plant Sciences, University of California, Davis, CA, USA High pressure and thermal treatments induce changes in membrane permeability which, above a threshold of high pressure and temperature, cause loss of cell compartmentation and texture modification. In the present study, integrity of onion cells before and after treatment was assessed by different methods. To obtain information on membrane permeability and cell compartmentalization, 1H-NMR T2 relaxation, conductivity measurements, enzymatic analysis (alliinase) and cell viability determi-
nation after neutral red staining of cell vacuoles were used. Texture analysis of samples was carried out with a TA.XT2 texture analyzer. High pressure treatments consisted of 5 minute holding times at 50, 100, 200, 300 or 600 MPa. Thermal treatments consisted of 30 minute water bath exposure to 40, 50, 60, 70 or 90 °C. All treatments were compared to raw onions. Membrane rupture could clearly be identified at 300 MPa and above in high pressure treatments and at 60 °C and above in thermal treatments. Membrane destabilization effects could already be visualized at 200 MPa and 50 °C treatments. The data suggests that the texture of onions is influenced by the state of the membranes and is abruptly modified once membrane integrity is lost. (Conflicts of interest: None declared. Source of funding: None declared.) doi:10.1016/j.cryobiol.2008.10.120