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Observations on the instrumental measurements of liquid food stickiness
1 , * 2
1  School of Biosciences, Faculty of Science, University of Nottingham, Nottingham, UK
2  University of Nottingham

https://doi.org/10.3390/foods_2020-07714 (registering DOI)
Abstract:

While we encounter sticky liquids in our daily life and are able to discriminate between them, relating instrumental measurements of stickiness to sensory perception remains to be a significant challenge in the context of the rational product design. In this paper we use the extensional flow analysis to examine some of the factors (probe withdrawal velocity, total contact area and total perimeter of probe) that influence instrumental measurements of stickiness in sticky liquid foods. Shortcomings of using the maximum peak or the area under the force-vs-time curve are discussed. In addition, we introduce a method where we use a series of probes with the varying ratio of the probe perimeter (P) over the probe area (A). By extrapolating parameters of the extensional force curve to the zero value of P/A we can obtain the values of the force at the maximum negative peak, gradient of the linear portion of the curve, distance to reach the maximum pull-off force for an effective zero perimeter probe. This “zero-perimeter” approach allows us to compensate for the changes in the meniscus and obtain extrapolated measures of stickiness independent of the probe perimeter. Results show that the linear region at the start of probe withdrawal during which time the perimeter is fully in contact with the liquid, might be a better correlation with stickiness compared to other parts of the curve. The dependency of the zero-perimeter corrected measured of stickiness on extensional speed showed a power law dependence for a ranged of fluids with different viscosity. In agreement with reports by other authors, we find that the extensional speed determines the type of failure (cohesive or adhesive) of the liquid column.

Keywords: stickiness, instrumental measurement, initial gradient, zero perimeter probe
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Ursula Gonzales-Barron
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