Storage time effect on the rheology of refrigerated potato tissue (cv. Monalisa)

Potato tubers were held in refrigerated storage and their firmness periodically sampled over a period of 140 days. At each sampling, the rheological properties uniaxial compression, shear, uniaxial tension, successive cycles of stress relaxation, creep compliance and texture profile analysis were determined, as was moisture content. Compression energy, maximum shear force, longitudinal tension stiffness and maximum tension deformation, stress relaxation parameters and moisture content were all significantly affected by storage time. Relaxed forces decreased consistently and linearly with time over a 140-day storage period, reflecting the decrease in cell turgor pressure resulting from the predominance of water loss through evaporation over water production. Longitudinal tension stiffness and maximum shear force increased linearly in the early stages, reflecting the increase in cell wall stiffness and elastic tissue behavior. Maximum tension deformation increased linearly with time reflecting the plastic deformation of the cell wall caused by growth in cell turgor pressure at early stages. Changes in the trends of rheological parameters over 140, 64 and 28 days evidenced the importance of extending the time period considered for rheological parameters of potato tissue. © Springer-Verlag 2000.Peer Reviewe