Inhomogeneous consistency of crystallized fat

In this study, the degree of inhomogeneity in crystallized fat samples was evaluated in terms of texture, solid fat content, microstructure, and triacylglycerol (TAG) composition. Four different cocoa butter alternatives based on symmetric or asymmetric monounsaturated TAGs and with different contents of palmitic acid (a POP-rich fat and a PPO-rich fat) and steric acid (a SOS-rich fat and a PSO-rich fat) were studied. Significant differences (P<0.001) in hardness between top and bottom was observed for all fats except the PSO-rich fat. The inhomogeneous consistency was shown to be a consequence of microstructural variation within the crystallized fats. No differences in solid to liquid ratio, melting points, or polymorphic behavior between top and bottom of fats were found. Sedimentation during the crystallization process could explain the observed inhomogeneity. Although sedimentation most likely is limited to the early stages of the crystallization process due to network formation, sedimented crystals influence the crystallization kinetics and thus introduce microstructural variations. This hypothesis is supported by findings of a higher amount of trisaturated TAGs in the bottom compared with the top of crystallized fats. The PSO-rich fat crystallizes fast compared with the other evaluated fats, which explains the more homogeneous texture of the PSO-rich fat compared with the other evaluated fats. Practical applications: Fat crystallization plays an important role for the texture of many food products such as chocolates, confectioneries, margarine, and butter. Correct analysis of texture is thus critical when evaluating fats for the food industry. This study emphasizes that inhomogeneity in the consistency could be of practical importance for evaluation of the mechanical and textural properties of crystallized fats for instance by compression tests or small deformation rheological testing of fat samples prepared in molds or with needle penetration tests, which only include the top of a fat sample.