Evaluation of the hardness and fracturability of crisps using a hemispherical probe.
The textural qualities of crisps can be assessed using the CT3 Texture Analyser. The potato crisp is supported at two points on a snack pot fixture (TA-DEC pot). As the test starts, the probe moves downward toward the sample, until it detects an initial resistance of a given load (trigger force) at the sample surface before proceeding rapidly to compress the sample over a specified distance. The test causes the crisp to break in half at the weakest point.
Crisp hardness is determined by the maximum force on the graph. This correlates with the force required to break the sample between the molars. The area under the graph is a measurement of work done that correlates with the chewing energy required to overcome the strength of the internal bonds within the sample. The fracturability value, which is the initial fracture or first fracture of the crisp, is an indication of the crispís brittleness.
Using these textural measurements, the quality of crisps can be assessed to meet customer satisfaction. The breaking characteristics of crisps are very useful in the development process for optimising product formulation, cook times, and moisture content of the raw product, as well as verifying the ideal sensory preference of the product.
Figure 1 shows the fracturability of a crisp using the hemispherical probe. The maximum force value is a measure of sample firmness/hardness (force required to initiate breaking of the sample between the molars). The fractures give an indication of the crunchiness of the sample. The area under the curve from the start of the test to the maximum force value is a measure of work done (energy required to break the strength of the internal bonds within the sample by the molars). Testes have been performed at room temperature.
Figure 2 shows force vs. distance for the fracturability of a crisp using a hemispherical probe. Tests have been performed at room temperature. The maximum force value is a measure of sample hardness. This is the amount of force required to break the sample between the molars. The area under the graph from the start of the test to the target distance point (3 mm) is a measure of work done. This is the energy required to break the strength of the internal bonds within the sample. From the graph, the sample is broken well before the target distance has been attained (seen by the sudden drop in force to zero load) but the probe continues to travel to attain the target distance before the return stroke to its starting position. The horizontal line along the x-axis shows the distance the plunger travels in returning to its starting position. (The negative distance values indicate a travel distance of 4.5 mm before the probe makes contact with the crisp).
When a trigger force of 5 g has been attained at the sample surface, the probe proceeds to apply an increasing force on the sample at a speed of 1 mm/s until it breaks. The maximum force required to break the sample is a measure of sample hardness. The area under the graph from the start of the test to the maximum force value (Figure 1) or to the target distance of 3 mm (Figure 2) is a measure of work done. As the probe penetrates the sample, fluctuations in the force values indicate that multiple fractures are taking place.
The table below summarises the results.
The fracturability value is particularly useful when comparing different brands of a sample. Fracturability value is an indication of sample brittleness. The test can be used to facilitate consistency in production and quality control, optimise the textural attributes of a product, perform shelf-life trials, and predict consumerís perception of a product.