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Foods 2017, 6(4), 31;

Validation of a Novel Technique and Evaluation of the Surface Free Energy of Food

Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Straße 35, Freising 85354, Germany
Chair for Food Packaging Technology, Technische Universität München, Weihenstephaner Steig 22, Freising 85354, Germany
Author to whom correspondence should be addressed.
Academic Editor: Danyang Ying
Received: 6 March 2017 / Revised: 12 April 2017 / Accepted: 17 April 2017 / Published: 20 April 2017
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Characterizing the physical properties of a surface is largely dependent on determining the contact angle exhibited by a liquid. Contact angles on the surfaces of rough and irregularly-shaped food samples are difficult to measure using a contact angle meter (goniometer). As a consequence, values for the surface energy and its components can be mismeasured. The aim of this work was to use a novel contact angle measurement method, namely the snake-based ImageJ program, to accurately measure the contact angles of rough and irregular shapes, such as food samples, and so enable more accurate calculation of the surface energy of food materials. In order to validate the novel technique, the contact angles of three different test liquids on four different smooth polymer films were measured using both the ImageJ software with the DropSnake plugin and the widely used contact angle meter. The distributions of the values obtained by the two methods were different. Therefore, the contact angles, surface energies, and polar and dispersive components of plastic films obtained using the ImageJ program and the Drop Shape Analyzer (DSA) were interpreted with the help of simple linear regression analysis. As case studies, the superficial characteristics of strawberry and endive salad epicarp were measured with the ImageJ program and the results were interpreted with the Drop Shape Analyzer equivalent according to our regression models. The data indicated that the ImageJ program can be successfully used for contact angle determination of rough and strongly hydrophobic surfaces, such as strawberry epicarp. However, for the special geometry of droplets on slightly hydrophobic surfaces, such as salad leaves, the program code interpolation part can be altered. View Full-Text
Keywords: contact angle; surface energy; edible coating; image processing; drop shape analysis; food contact angle; surface energy; edible coating; image processing; drop shape analysis; food

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Senturk Parreidt, T.; Schmid, M.; Hauser, C. Validation of a Novel Technique and Evaluation of the Surface Free Energy of Food. Foods 2017, 6, 31.

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