Relative Hardness of Fat Crystal Networks Using Force Displacement Curves

The use of automated penetration measurements as a means to evaluate the hardness of lipid crystal networks is ubiquitous in the literature, but lacks consistency in the methodology applied, or the analysis used. This study provides a framework for the standardization of methodology and parameters used to measure hardness. A relatively large variety of lipid samples of varying hardness were tested with a texture analyzer. Penetration depth, speed, and probe type were independently varied to determine the optimum procedure with which to obtain force-displacement curves, and a variety of analysis techniques were considered to interpret these curves. Optimal curves were obtained at a penetration speed of 0.5 mm/s, using a constant penetration depth of 1.5 mm, and either a needle or ball probe depending upon the hardness or nature of the sample. The maximum force parameter was found to be the most unambiguous measure of hardness. The results from maximum force show close correlation with that from cone penetrometry—a method widely used in industry.