While many of us experience an emotional response when eating chocolate, practical material science is responsible for the special appeal that makes chocolate one of the world’s most loved treats.
. Image Credit: NETZSCH-Gerätebau GmbH
The Kinexus Rotational Rheometer can help perfect the mouthfeel of chocolate for optimal creaminess and smoothness.
In a previous article, it was explained how rheology helps enhance both the bite and the flavor of the solid chocolate bar above the melting point as well as how to optimize chocolate processing.
This article discusses the science of optimizing the mouthfeel of chocolate for desired creaminess and smoothness. The composition and taste preferences of various chocolate types differ all over the world. Furthermore, trends often demand low fat/sugar alternatives that must satisfy consumer expectations.
In the laboratory environment, it can be a complicated task when quantifying the sensory properties (creaminess/smoothness) in a way that satisfies the consumer experience during the development of new products.
Rheology for the Perfect Mouthfeel of Chocolate
Extending traditional rotational rheometry by deploying the axial capacities of the Kinexus rheometer enables the simulation of mastication or the action of chewing.
Using this test, hardness, yield stress, coating of the roof of the mouth and stickiness of the chocolate can be evaluated objectively. The general force variations produced during a measurement offer an indication of how the chocolate will flow, melt and coat the mouth during mastication.
Figure 1. A parallel plate measuring system mimicking chewing of chocolate. Image Credit: NETZSCH-Gerätebau GmbH
Rheology can be employed to replicate real-life processes and, in this instance, the mouthfeel and chewing of chocolate. Squeeze flow imitates both the pressing of the tongue against the palate, as well as the tooth contact. Rotational shear simulates flow within the mouth around the tongue.
During this cyclical test, the material is subjected to both shear and normal (squeeze) forces. As the gap undergoes compression, the normal force increases (Figure 2, point A), which may relate to the hardness or consistency of the sample. The force applied after initial compression is the yield stress of the chocolate (Figure 2, point B).
As the normal force reaches zero, the area under the curve demonstrates how long the chocolate maintains contact with the upper plate. This imitates how the chocolate coats the roof of the mouth.
As the gap increases once again, a negative normal force is observed, which could be seen as adhesiveness (figure 2, point C). After decompression, any residual force is related to the chocolate’s “stickiness” (figure 2, point D).
Figure 2. The mastication test. A = consistency, B = yield stress, C = adhesiveness, D = stickiness. Image Credit: NETZSCH-Gerätebau GmbH
Mastication Simulation of Different Milk Chocolates
Mastication simulation was applied to three different milk chocolates by performing a normal force and shear measurement on the Kinexus (Figure 3). The softest consistency is observed in the premium chocolate, and the enrobing chocolate is considerably harder.
The enrobing chocolate’s yield stress is also considered to be high meaning this chocolate will coat the mouth for a prolonged period of time in contrast to both of the bar chocolates. This gives the consumer a pleasant chocolate hit despite the product’s low proportion of chocolate (this product will contain a center).
The premium chocolate possesses the least adhesiveness and stickiness. A desired feature as high adhesiveness or stickiness can be affiliated with a cloying mouthfeel.
As the enrobed chocolate product has less chocolate present, these parameters have less influence on the consumer experience during consumption in contrast to a chocolate bar.
Figure 3. Normal force vs experiment time for milk chocolate during a mastication simulation test. Image Credit: NETZSCH-Gerätebau GmbH
Enhanced understanding of rheological properties of chocolate is key to the optimization of processes, as well as achieving constant product quality and fulfilling customer expectations.
Employing rheology to simulate mastication facilitates the prediction and control of the structural changes in the chocolate during consumption.
References
- Friction Measurements with Molten Chocolate | SpringerLink
- De Graef, V., Depypere, F., Minnaert, M., & Dewettinck, K. (2011). Chocolate yield stress as measured by oscillatory rheology. Food Research International, 44(9), 2660–2665.
- Chung, C. et al. (2012) Instrumental mastication assay for texture assessment of semi-solid foods: compile cyclic squeezing flow and shear viscometry. Food research international, 49, p161-169
This information has been sourced, reviewed and adapted from materials provided by NETZSCH-Gerätebau GmbH.
For more information on this source, please visit NETZSCH-Gerätebau GmbH.