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Modeling the Mechanical Texture of Foxtail Millet Extrudates during Hydrosorption with a Modified Peleg-Fermi Model
並列摘要
The objective of this study was to monitor and model the texture changes of foxtail millet extrudates with different structural properties as a function of water activity (a_w). Four extrudates, after equilibrated at a_w of 0.113- 0.97, were compressed using a TA.XT2 Texture Analyzer. Two force-related texture parameters, Peak Force (PF) and Total Work (TW) and two jaggedness-related, Number of Spatial Ruptures (NSR) and Specific Ling Length (SLL), were extracted from their force-displacement curves. Water sorption led to loss of jaggedness of their forcedisplacement curves. All the four texture parameters decreased when aw increased to a certain value. Before the decrease occurring, TW and PF increased for all the extrudates with a_w increase, while SLL increase was observed only for two extrudates and no NSR increase was observed for all extrudates. The critical water activity (a_(wc)) where texture parameters decreased rapidly ranged between 0.42 and 0.83 depending mainly on the kinds of the extrudates and to some extent on the texture parameters studied. The extrudates with coarse structure exhibited lower forcerelated values, while the extrudates with fine structure exhibited lower jaggedness-related values. Crispness index, a combination of force- and jaggedness-related texture criteria, decreased almost linearly as a_w increase up to 0.61~0.66 for all the extrudtes. The Peleg-Fermi equation can satisfactorily model the changes in jaggedness-related texture parameters as a function of a_w. A modified form of the Peleg-Fermi equation, proposed in this study, was needed to model the changes of force-related parameters better.