Evaluation of the Influence of Coating and Coating Composition on the Sorption Properties of Freeze-Dried Carrot Bars
2025
Agnieszka Ciurzyńska | Magdalena Karwacka | Monika Janowicz | Sabina Galus
This study aimed to investigate the effect of dip coating and the composition of the applied coating on the structure and sorption properties of freeze-dried carrot bars. The scope of the work included preparing freeze-dried carrot bars, coating them with coatings of different gelatin concentrations, and then analysing the sorption properties based on sorption isotherms. Additionally, the structure was assessed based on porosity, shrinkage, and microscopic observations. Water activity and dry matter content were also measured. Analysis of the obtained results showed that coating caused a significant increase in water activity and a decrease in the dry matter content of freeze-dried carrot bars. There was also a decrease in porosity and volume compared to the control sample, which was confirmed by microscopic analysis. The study of sorption kinetics showed that the coatings limited the hygroscopicity of the samples, reducing the dynamics of moisture adsorption and accelerating the stabilisation of water content. The best model describing the sorption isotherms was the Peleg model, and the isotherms themselves were classified as type IIb according to the Blahovec and Yanniotis classification. The composition of the coating significantly affects the structure and selected physical properties of the bars. FT-IR analysis did not show any significant changes in the bars&rsquo: chemical structure.
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