TOWARD PREDICTION OF POROSITY IN FOODS DURING DRYING: A BRIEF REVIEW

Four generic trends of pore formation during drying are identified from the literature. The present prediction methods are mainly based on empirical correlations. It is common to correlate porosity with water content by quadratic, polynomial, or exponential forms of equations, which do not provide insight into the physics of the process. The glass transition theory is one of the proposed concepts to explain the process of shrinkage and collapse during drying. However, the glass transition theory does not hold true for all products. Other concepts, such as surface tension, structure, environment pressure, and mechanisms of moisture transport also play important roles in explaining the formation of pores. It is hypothesized that as capillary force is the main force responsible for collapse, so counterbalancing this force causes formation of pores and lower shrinkage.

[1]  M. Karel,et al.  Structural collapse of plant materials during freeze-drying , 1996 .

[2]  X. D. Chen,et al.  Density, shrinkage and porosity of calamari mantle meat during air drying in a cabinet dryer as a function of water content , 1996 .

[3]  A. Chiralt,et al.  Mechanical and Structural Changes in Apple (Var. Granny Smith) Due to Vacuum Impregnation with Cryoprotectants , 1998 .

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

[5]  W. Senadeera,et al.  Change of physical properties of green beans during drying and its influence on fluidization , 1998 .

[6]  K. Autio,et al.  Relationships between flour/dough microstructure and dough handling and baking properties , 1997 .

[7]  C. Ratti.  Shrinkage during drying of foodstuffs , 1994 .

[8]  H. H Nijhuis,et al.  Approaches to improving the quality of dried fruit and vegetables , 1998 .

[9]  Julian F. V. Vincent,et al.  Relationship between density and stiffness of apple flesh , 1989 .

[10]  S. Rizvi,et al.  Mechanical properties of protein‐stabilized starch‐based supercritical fluid extrudates , 2000 .

[11]  C. Christensen.  Food Texture Perception , 1984 .

[12]  Martin G. Scanlon,et al.  Shear stiffness and density in potato parenchyma , 1998 .

[13]  J. Lombraña,et al.  The influence of pressure and temperature on freeze-drying in an adsorbent medium and establishment of drying strategies , 1997 .

[14]  M. Hanna,et al.  Physical and Molecular Properties of Re-extruded Starches as Affected by Extruder Screw Configuration , 1996 .

[15]  V. Gekas,et al.  Osmotic dehydration of apples. Shrinkage phenomena and the significance of initial structure on mass transfer rates , 1998 .

[16]  R. S. Rapusas,et al.  Thermophysical properties of fresh and dried white onion slices , 1995 .

[17]  Malcolm C. Bourne,et al.  A PSYCHOACOUSTICAL THEORY OF CRISPNESS , 1976 .

[18]  F. Wolfe,et al.  Porosity in cooked beef from controlled atmosphere packaging is caused by rapid CO2 gas evolution , 1996 .

[19]  P. S. Madamba,et al.  BULK DENSITY, POROSITY AND RESISTANCE TO AIRFLOW OF GARLIC SLICES , 1993 .

[20]  Martin R. Okos,et al.  Predicting the Quality of Dehydrated Foods and Biopolymers — Research Needs and Opportunities , 1996 .

[21]  M. Hanna,et al.  Modification of Microstructure of Starch Extruded With Selected Lipids , 1997 .

[22]  Conrad O. Perera,et al.  Color and density of apple cubes dried in air and modified atmosphere , 1998 .

[23]  A. I. Liapis,et al.  Research and Development Needs and Opportunities in Freeze Drying , 1996 .

[24]  A. Chiralt,et al.  EQUILIBRATION OF APPLE TISSUE IN OSMOTIC DEHYDRATION: MICROSTRUCTURAL CHANGES , 1999 .

[25]  A. Calvelo,et al.  Modeling the Thermal Conductivity of Cooked Meat , 1984 .

[26]  V. Karathanos.  COLLAPSE OF STRUCTURE DURING DRYING OF CELERY , 1993 .

[27]  J. Aguilera,et al.  Glass transitions and shrinkage during drying and storage of osmosed apple pieces , 1998 .

[28]  G. Ponchel,et al.  Fat Bloom and Chocolate Structure Studied by Mercury Porosimetry , 1997 .

[29]  E. Gutman,et al.  Thermal analysis of the polymerization process on the surface of inorganic fillers , 1996 .

[30]  Enrique Rotstein,et al.  Prediction of Thermal Conductivity of Vegetable Foods by the Effective Medium Theory , 1986 .

[31]  John R. Mitchell,et al.  The effect of sugars on the extrusion of maize grits: I. The role of the glass transition in determining product density and shape , 1996 .

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

[33]  T. Furuta,et al.  Thermodynamically Interactive Heat and Mass Transfer Coupled With Shrinkage and Chemical Reactions , 1989 .

[34]  J. T. Clayton,et al.  Characterization of the pore structure of starch based food materials. Discussion , 1992 .

[35]  Christine H. Scaman,et al.  Characterization of vacuum microwave, air and freeze dried carrot slices , 1998 .

[36]  W. Pietsch.  Readily engineer agglomerates with special properties from micro- and nanosized particles , 1999 .

[37]  I. Saguy,et al.  Physical Properties of Alginate−Starch Cellular Sponges , 1998 .

[38]  I. Saguy,et al.  Tailor-made porous solid foods , 1997 .

[39]  Michael J. Pikal,et al.  The collapse temperature in freeze drying: Dependence on measurement methodology and rate of water removal from the glassy phase , 1990 .

[40]  E. Berghofer,et al.  Extrusion Cooking of Rice Flour and Amaranth Blends , 1999 .

[41]  R. J. Hutchinson,et al.  Influence of processing variables on the mechanical properties of extruded maize , 1987 .