Penetration testing is very similar to compression testing with one key difference, the penetrometer probe is typically much smaller than the sample being tested and 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. This test method can be performed on a wide variety of food products and is a very useful test in simulating a bite or in comparative analysis.
With penetrometry-based methods, it is most common that the probe is penetrated into a sample to a given distance and the peak force encountered during the test is measured. This however can be different when the product has a skin, such as an apple. Penetration probes come in a multitude of sizes and shape and the selection of the correct one can seem a bit daunting. There are cylindrical probes with sharp edges, radiused edges, and blunt tips. There are also conical shaped probes with sharp to wide angles. FTC can help with the correct selection for your particular product.
One must also consider the supporting mechanism for the sample in conducting penetration test. If the sample is quite thin, then the results can be altered as the test can become a penetration / compression test as the probe near the bottom support. In this case a bottom plate with a hole is employed and the test becomes more of a â€œpunch and dieâ€ test.