Static and advancing contact angles of water on dark chocolate
Author(s)
Baratian Ghorghi, Zohreh
Donkem, Judicaelle Labelle Akana
Tsague, Leonel Cedrick Mafotang
Date Issued
November 2026
Type
article
text::journal::journal article
Volume
418
Start Page
1
End Page
13
ISSN
0260-8774
Journal
Abstract
This work investigated the wettability of dark chocolate by water, focusing on commercial and laboratory-produced chocolate. The study employed optical tensiometry to measure the static and advancing contact angle. Sessile drop experiments on commercial chocolate demonstrated that water was neither absorbed nor subject to evaporation during the measurement period. Chocolate with higher sugar content exhibited lower contact angles, that is a more hydrophilic character. Furthermore, the higher sugar content resulted in greater droplet spreading during the measurement time, leading to greater deviations from the ideal behavior, corresponding to smooth, chemically uniform, and inert surfaces. A more hydrophilic and less ideal character was also observed for non-tempered chocolate compared to its tempered counterpart. We hypothesized that the hydrophilic character of chocolate, among other factors, is conferred by sugar, which the wetting water can access through surface irregularities such as cracks and pores. This mechanism, which is introduced as a novel explanation of the phenomenon, was supported by NMR analysis of the liquid after contact with the chocolate, which showed sugar contamination. Such irregularities depend on the chocolate composition and process conditions and are exacerbated in poorly tempered chocolate. The difference between the advancing and static contact angle was larger for non-tempered samples, suggesting that surface non-idealities such as roughness and solid dissolution are more important in non-tempered samples. This research contributes to a deeper understanding of the wetting behavior of chocolate and opens the way to the use of contact angle measurements in the chocolate field as an easy-to-measure parameter for assessing chocolate surface characteristics and supporting quality-control practices.
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contact angle-2026.pdf
Size
4.33 MB
Format
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