Water Sorption Analysis on Vegetables Using Modified Dubinin–Astakhov Parameters

Abstract

The parameters of a modified Dubinin–Astakhov (DA) equation were studied for six kinds of fresh vegetables. The equilibrium moisture content data were fitted to the modified DA equation under the condition that the limit of the moisture content of the adsorption space represented by M ₀ was assumed to be roughly equal to the equilibrium moisture content at the relative humidity of 97.3%. Then we calculated other two DA parameters of n and A _e . The former is the distribution index of the Weibull probability density function, and the latter is a characteristic energy. In addition, the logarithm of the value increased proportionally with the increase of the n value, and the A _e value could be experimentally identified by the degree of the pore inside the vegetable. Moreover, we discussed the relationship between the DA parameter M ₀ and the moisture content M _m calculated with the monolayer adsorption capacity defined by a Brunauer–Emmett–Teller equation. As the results, the logarithm of M ₀ approximately represented the direct proportion to that of M _m among all tested vegetables. This showed the power low relationship between M ₀ and M _m , and the slope of the line could mean the fractal dimension of the moisture sorption space.

Keywords:

• Water sorption
• Vegetable
• Geometrical structure
• Modified DA equation
• BET equation

Acknowledgments

A part of this study is financially supported by the Grant-in-Aid for Encouragement of Young Scientists. We would like to thank the Japan Society for the Promotion of Science.