Water Activity and Its Estimation in Food Systems: Theoretical Aspects

Berg, Cornelis A.T. van den; Bruin, S.

doi:10.1016/b978-0-12-591350-8.50007-3

Cited by 396 publications

(292 citation statements)

References 86 publications

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“…According to Skaar (1988), 77 mathematical equations predicting the sorption isotherms of different biological materials including wood are listed in Van den Berg and Bruin (1981), of which many were found by Boquet et al (1980) to be mathematically equivalent. Many of them coincided with the second-degree polynomial expression first presented by Hailwood and Horrobin (1946).…”

Section: Sorption Isothermmentioning

confidence: 99%

A critical discussion of the physics of wood–water interactions

et al. 2012

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This paper reviews recent findings on wood-water interaction and puts them into context of established knowledge in the field. Several new findings challenge prevalent theories and are critically discussed in an attempt to advance current knowledge and highlight gaps. The focus of this review is put on water in the broadest concept of wood products, that is, the living tree is not considered. Moreover, the review covers the basic wood-water relation, states and transitions. Secondary effects such as the ability of water to alter physical properties of wood are only discussed in cases where there is an influence on state and/or transition.

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Section: Sorption Isothermmentioning

confidence: 99%

A critical discussion of the physics of wood–water interactions

et al. 2012

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“…The temperature dependence of the equilibrium moisture content has an important practical bearing on chemical and microbiological reactions associated with spoilage (Al-Muhtaseb et al 2004). At the same moisture content, higher temperatures entail a higher water activity and consequently faster rates of deterioration ( Van den Berg and Bruin 1981).…”

Section: Sorption Isothermmentioning

confidence: 99%

“…They give information about the water sorption mechanism and interactions between food components and water. They are also extremely important in modelling of the drying process, in design and optimisation of drying equipment, in predicting shelf-life stability, in determining critical moisture, in selecting appropriate packaging material and water activity for acceptability of products that deteriorate mainly by moisture gain (Van den Berg and Bruin 1981;Gal 1987;Palou et al 1997;Arora et al 2003;Kaymak-Ertekin and Gedik 2004).…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic analysis of sorption isotherms of cassava (Manihot esculenta)

et al. 2012

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Sorption isotherms of cassava were determined experimentally using a static gravimetric method at 30, 45 and 60°C and within the range of 0.10-0.90 water activity. At a constant water activity, equilibrium moisture content decreased with increasing temperature. The equilibrium moisture content increased with increasing water activity at a given temperature. The experimental results were modelled using seven sorption models using non-linear regression technique. Results demonstrated that the GAB model adequately predicted equilibrium moisture content of cassava for the range of temperatures and water activities studied. The thermodynamic functions such as net isosteric heat of sorption, differential entropy of sorption, net integral enthalpy and entropy were evaluated to provide an understanding of the properties of water and energy requirements associated with the sorption behaviour. Net isosteric heat and differential entropy decreased with increasing equilibrium moisture content. The net integral enthalpy decreased while net integral entropy increased with increasing equilibrium moisture content. Net integral entropy was negative in value. All thermodynamic functions were adequately characterised by a power law model. The point of maximum stability was found between 0.053 and 0.154 kg water/kg db for cassava.

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“…Each of those generated models has proven successful to various extents in the approximation of the equilibrium moisture data of a given type of food material within an appropriate range of a w . Van den Berg and Bruin (1981) [25] conducted a survey of 77 models classified into three groups: theoretical, partially theoretical and fully empirical. The power series of Jaroniec (1975) [26], which represents a family of water sorption isotherm models, was also included:…”

Section: Adsorption Isotherms Of Pear Tissuementioning

confidence: 99%