Testing cooked individual vegetable texture

Most vegetables are cooked before consumption, a process that softens their texture (unless there is a lot of lignification) and gelatinises the starch deposited as food for the plant.

Starch and protein deposits are particularly abundant in beans, peas, and corn picked at maturity. A sugar to starch equilibrium reaction occurs during the storage of some vegetables, and this can affect their texture.

Sweetcorn and sweet peas when picked immature have much sugar and a succulent texture. Within hours the texture of sweetcorn can become tougher and drier due to sugar conversion to starch.

Typical test using Volodkevich Bite Jaws

Sweetcorn toughness can be measured using Volodkevich Bite Jaws, a fixture that performs an imitative test by simulating the action of an incisor tooth biting through food. A kernel is placed centrally on the lower jaw and the upper jaw moves down to shear the sample. Toughness is measured by using an automatic analysis macro to calculate the area under the force-time graph on the downward stroke.

Products which have non-homogeneous textures such as a lettuce consisting of different layers present a testing challenge. While it is relatively easy to quantify the firmness of a homogeneous sample using a standard penetration probe, variable products such as these are inevitably difficult to measure as the sample layers present at random.

A standard penetration test on a non-uniform product is likely to have very low reproducibility. A Multiple Puncture Probe provides multiple penetration probes that enter the sample at multiple sites thereby creating an averaging effect which produces a much greater repeatability for an otherwise variable product.