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Extended dynamic vapor sorption of glutinous rice flour observed in logarithmic time scale and its modeling as a process with varying activation energy
Author(s) -
Zhao Xuewei,
Zhang Hua,
Li Xingke,
Fan Wen
Publication year - 2020
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/jfpe.13572
Subject(s) - desorption , sorption , adsorption , kinetic energy , activation energy , chemistry , mass transfer , water vapor , diffusion , thermodynamics , relative humidity , thermal diffusivity , logarithm , kinetics , analytical chemistry (journal) , chromatography , organic chemistry , mathematics , physics , mathematical analysis , quantum mechanics
With the objective of characterizing water sorption kinetics of glutinous rice flour during extended water vapor exposure, water adsorption and desorption measurements were conducted at nine relative humidity (RH) levels for up to 1,500 min per step, and displayed in a logarithmic time scale. A three‐stage sorption kinetics was observed, and the final stage was characterized with a very long and slow process. The final sections of the kinetic curves were concave to log( t ) axis for adsorption while linear for desorption, even after the flour was gelatinized. Increment in RH step and flour particle size, and variation in water content can only postpone starting of the linear stage. Analysis using an Elovich‐type model indicated that both adsorption and desorption can be treated as processes whose activation energy varied consistently during sorption. Reaction order difference between adsorption and desorption was the major contributor to their distinct kinetic responses in the final stages. Practical Applications Water sorption kinetic measurements are necessary for exploring mass transfer mechanism, and determining parameters such as water diffusivity and interfacial mass transfer coefficient. Extended measurement duration allows one to catch the entire characteristics of a kinetic process. Distinct kinetic features between adsorption and desorption of glutinous rice flour were observed when the data were plotted against logarithm of time. The later stage was a slow process. Further analysis using an Elovich‐type model indicated that both adsorption and desorption were processes with varying activation energy. This information can be potentially helpful in optimizing both the quality of food product and the economics of many food processes involving water transfer.