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EXPERIMENTAL DETERMINATION OF MASS TRANSFER COEFFICIENT: MOISTURE CONTENT AND HUMIDITY RATIO DRIVING FORCE APPROACHES DURING BAKING
Author(s) -
DEMIRKOL EREN,
ERDOGDU FERRUH,
PALAZOGLU T. KORAY
Publication year - 2006
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2006.00056.x
Subject(s) - mass transfer , mass transfer coefficient , water content , convection , diffusion , mechanics , moisture , thermodynamics , humidity , natural convection , quality (philosophy) , heat transfer coefficient , chemistry , materials science , heat transfer , composite material , physics , geotechnical engineering , quantum mechanics , engineering
Moisture distribution in baked products at the end of baking is important because it directly affects the product's quality. In fact, nonhomogeneous moisture distribution may result in quality defects such as cracking, checking etc. Diffusion inside and convective mass transfer outside the product are important factors affecting the quality. Therefore, accurate values of mass transfer parameters should be known for optimization of the baking process to obtain a product of higher quality. For this objective, infinite mass transfer and constant diffusion coefficient simplifying approximations have been applied in the literature numerous times to develop mass transfer models. However, the infinite mass transfer coefficient approximation may not hold true, especially under natural convection conditions. To evaluate the mass transfer coefficient, baking experiments were carried out to obtain the moisture content changes of cookies during baking at 190, 200 and 210C under natural and forced convection conditions. Then, mass transfer coefficient was determined using the moisture content difference and the humidity ratio difference as the driving force for mass transfer. The results of these two approaches were compared, and the use of humidity ratio difference seemed to be a better approach in terms of reflecting actual process conditions because it is based on the surface changes.