Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C.
Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w)               , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w)               . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w)                tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T               (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T               (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.
Department of Analytical Chemistry, University of Pardubice, Pardubice, Czech Republic. libor.cervenka@seznam.cz
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Cervenka
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Kubínová
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Juszczak
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M
Witczak
D000327:Adsorption; D031170:Arctium / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning / Q000379:methods; D055598:Chemical Phenomena; D061353:Food Storage / Q000379:methods; D038143:Inula / Q000737:chemistry*; D008962:Models, Theoretical; D018517:Plant Roots / Q000737:chemistry*; D044366:Transition Temperature; D014867:Water / Q000737:chemistry
D014867:Water