Friction Measurements with Molten Chocolate

Abstract

A novel test is reported which allows the measurement of the friction of molten chocolate in a model tongue-palate rubbing contact. Friction was measured over a rubbing period of 150 s for a range of commercial samples with different cocoa content (85-5% w/w). Most of the friction curves had a characteristic pattern: initially a rapid increase occurs as the highviscosity chocolate melt is sheared in the contact region followed by friction drop as the film breaks down. The exceptions were the very high (85%) and very low (~ 5%) cocoa content samples which gave fairly constant friction traces over the test time. Differences were observed in the initial maximum and final friction coefficients depending on chocolate composition. Generally, the initial maximum friction increased with increasing cocoa content. At the end of the test, the rubbed films on the lower slide were examined by optical microscopy and infrared micro-reflection spectroscopy. In the rubbed track, the chocolate structure was severely degraded and predominately composed of lipid droplets, which was confirmed by the IR spectra. The new test provides a method to distinguish between the friction behaviour of different chocolate formulations in a rubbing low-pressure contact. It also allows us to identify changes in the degraded chocolate film that can be linked to the friction profile. Further development of the test method is required to improve simulation of the tongue-palate contact including the effect of saliva and this will be the next stage of the research.

Nonlinear friction dynamics in the cognitive process of food textures: Thickness of polysaccharide solution

“…Previous research has indicated that the temporal change in friction affects food texture and tactile texture. For example, Masen and Cann (2018) reported that the friction profile of chocolate changed with the cocoa content of chocolate. The initial maximum friction coefficient increased with increasing cocoa content.…”

Measurement of molten chocolate friction under simulated tongue-palate kinematics: Effect of cocoa solids content and aeration

“…However, there is considerable interest in the food industry in developing foods with reduced energy density, in the case of chocolate meaning less fat and sugar, but with the same mouthfeel. There are very few published papers reporting chocolate tribology ( Lee et al., 2002 ), ( Lee et al., 2004 ), ( Masen and Cann, 2018 ), ( Rodrigues et al., 2017 ), ( Breslin, 2013 ), ( van Aken et al., 2007 ) and even fewer relating friction properties to sensory perception ( Lee et al., 2004 ), ( Masen and Cann, 2018 ). A range of tribology test methods have been used including ball-on-flat ( Lee et al., 2002 ), ( Breslin, 2013 ), ( van Aken et al., 2007 ) and modified rotational viscometer ( Lee et al., 2004 ).…”

“…A range of tribology test methods have been used including ball-on-flat ( Lee et al., 2002 ), ( Breslin, 2013 ), ( van Aken et al., 2007 ) and modified rotational viscometer ( Lee et al., 2004 ). The studies usually compare friction/speed response for different chocolate manufacturing methods ( Lee et al., 2004 ) or composition ( Lee et al., 2004 ), ( Masen and Cann, 2018 ). In consumer sensory tests of chocolate texture, the smoothness is usually identified as a key characteristic ( Lee et al., 2004 ) and might be linked to reduced friction in the low speed boundary regime.…”

A rapid method to evaluate the chocolate smoothness based on the tribological measurement

“…The lubrication of molten chocolate was also strongly influenced by the presence of solid sugar particles and cocoa solids (Rodrigues et al, 2017. In addition, the differences in the initial maximum and final CoF were also observed and depended on the chocolate composition (Masen & Cann, 2018). Furthermore, the additives of magnesium stearate powder and plant sterol powder failed, affecting the melting behavior of chocolate but improved their CoF compared with the pure chocolates (Mantihal et al, 2019).…”