Quantification of microstructural changes during first stage air drying of grape tissue

Abstract Microstructural changes in cells of Ruby grape ( Vitis vinifera ) quarters were monitored during first stage of convective air drying, under a stereo-microscope. A gradual overall shrinkage of grape cells was observed during the process. The cellular parameters: area, perimeter, major and minor axis length, Feret diameter, elongation, roundness and compactness, were quantified by image analysis. It was verified that cell dimensions suffered modifications during drying, but their shape remained unchanged. These microstructural changes showed a smooth exponential decrease with time, and a first-order kinetic model was satisfactorily fitted to the data. Temperature increased the rate of cellular shrinkage and this effect followed an Arrhenius type behaviour. Increasing temperature from 20 to 60 °C resulted in a 350% increase of the area change rate. For the parameters related to cellular dimensions, the magnitude of the values were 10 −3 min −1 for the rate of change at 40 °C and 3 kJ/mol for the activation energy.

[1]  A. Crafts.  CELLULAR CHANGES IN CERTAIN FRUITS AND VEGETABLES DURING BLANCHING AND DEHYDRATION , 1944 .

[2]  N. N. Potter,et al.  Food Dehydration and Concentration , 1995 .

[3]  Gustavo V. Barbosa-Cánovas,et al.  Food Engineering 2000 , 1995 .

[4]  José Miguel Aguilera,et al.  Microstructural principles of food processing and engineering , 1999 .

[5]  H. Bolin,et al.  Scanning Electron Microscope/Image Analyzer Determination of Dimensional Postharvest Changes in Fruit Cells , 1987 .

[6]  Daryl Lund,et al.  CONSIDERATIONS IN CALCULATING KINETIC PARAMETERS FROM EXPERIMENTAL DATA , 1985 .

[7]  Baylee Ogletree,et al.  FRUITS AND VEGETABLES , 2001 .

[8]  Vassilis Gekas,et al.  Transport Phenomena of Foods and Biological Materials , 1992 .

[9]  P. Lillford,et al.  Microstructural and Imaging Analyses as Related to Food Engineering , 1997 .

[10]  Arun S. Mujumdar,et al.  Transport Phenomena of Foods and Biological Materials , 1993 .

[11]  Alan Shivers Foust,et al.  Principles of unit operations , 1960 .

[12]  V. Belessiotis,et al.  Development of porous structure during air drying of agricultural plant products , 1996 .

[13]  Arun S. Mujumdar,et al.  Drying of Fruits , 2004 .

[14]  J. G. Brennan,et al.  Changes in structure, density and porosity of potato during dehydration , 1995 .

[15]  J. G. Brennan.  Food dehydration : a dictionary and guide , 1994 .

[16]  H. Ramaswamy,et al.  Processing fruits : science and technology , 2005 .

[17]  Robert E. Brackett,et al.  Fruits and Vegetables , 2001 .

[18]  Brian P. Hills,et al.  NMR studies of changes in subcellular water compartmentation in parenchyma apple tissue during drying and freezing , 1997 .

[19]  D. Vives.  Principles of unit operations, 2nd edition (Foust, Alan S.; Wenzel Leonard A.; Clump, Curtis W.; Maus, Lois; Anderson, L. Bryce) , 1981 .