Characterisation of the work of adhesion of food grade coating materials on a maltodextrin model surface

The aim of the present study was to evaluate two models, the Owens-Wendt-Rabel and Kaelble model (OWRK) and the Young-Dupre model (YD), for characterisation of the wetting and adhesion properties of cellulose- and shellac-based coating solutions on a maltodextrin model surface (MDGSS). In addition, for the OWRK model, the impact of a variation in the combination of reference liquids on the free surface energy (SE), the contact angle (CA) and the work of adhesion (W-A) was investigated. Results of the present study demonstrate that the use of reference liquids covering a wide range of polar and disperse fraction of the SFT is recommended for the OWRK model. It was shown that at least the use of water and diiodomethane is needed for reliable values of the SE and the WA. Additional reference liquids, e.g., ethylene glycol or formamide, are recommended to obtain robust results. With respect to the coating solutions, the calculated contact angle according to the OWRK model did not provide qualified values due to an inappropriate combination of polar and disperse fractions of the SFT and the SE of MDGSS for methylcellulose, Nutrateric (R) and shellac. Results for the WA-OWRK and the WA-YD provided reliable data, but differed for all coating solutions. Therefore it is recommended to perform both analyses in comparative studies on particle-liquid-interactions. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.