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There are seven fundamental methods which form the basis of the mechanical testing for sensory texture attributes. These test types replicate all possible interactions between a consumer - or production processing or handling equipment - and the product itself.
Food Technology Corporation supplies fixtures which are designed to implement each test method.
Bulk analysis testing is used when it is not practical or representative to test an individual sample as a whole or component piece. Particulate products (e.g. reconstituted meats), or foodstuffs which contain small elements in an individual serving or mouthful (e.g. rice or beans), lend themselves to being analyzed “in bulk”. The test method combines compression, shearing and extrusion of the sample.
Compression testing is a common and valuable texture testing method. Pure compression places the sample on a flat surface and an upper fixture, larger than the sample in its deformed state, is lowered into the specimen. Texture Profile Analysis (TPA), is a specialized derivative of compression testing. Localised compression, with a smaller probe, is also useful and may result in penetration of the sample.
Extrusion testing has many applications for semi-solid products. The sample is normally placed in a cylindrical container and an upper fixture acts as a plunger to pass into the product, which flows either back around the probe (back extrusion method) or is forced out through an aperture in the base of the cell (forward extrusion method). Spreadabilty is tested with a conical probe and matching container.
Penetration testing is very similar to compression testing with one key difference, the probe is typically much smaller than the sample being tested. Penetration refers to when the probe passes completely through a sample (a thin tortilla) or an element of the product (the surface generally, or the skin of a piece of fruit). Puncture is similar, meaning the probe passes into the sample, though not necessarily exiting.
Shear testing applies slicing or “shearing” into or through the product, which replicates the action of the front incisors when food is introduced into the mouth. This method also measures the resistance of the sample to being cut by a knife, when preparing or serving to product.
Breaking or bending tests are commonly used for hard or brittle foods that snap. Some softer products are also tested with this method, where a degree of flexibility is desired, or intended to be minimised.
Tension methods pull or stretch the test sample, usually to measure the elasticity or extensibility, and the ultimate strength of the product. The texture analyzer may pull the sample apart by moving the crosshead upwards, or the fixtures may enable tension in the product, even when using the system in compression.