Diminishing Marginal Utility of Cooling Rate Increase on the Crystallization Behavior and Physical Properties of a Lipid Sample

摘要

It is well established that variation of the rate of cooling (r) of a lipid sample is an effective tool to influence the crystallization process and effect changes in network structure and physical functionality. However, the extent of the physical changes does not always justify the extent to which the cooling rate must be altered. It is therefore important to understand the rates at which marginal changes in physical functionality begin to diminish, and to understand the mechanisms which introduce such limitations. A commercially available cocoa butter alternative, Temcote (Bunge Oils, Bradley, IL), was crystallized under cooling rates varying from 0.1 to 20 °C min?1. The growth mode and polymorphism of each sample was studied using DSC and X-ray diffraction (XRD). The hardness of the sample was monitored using cone penetrometry and its solid fat content (SFC) evolution was monitored using a temperature controlled pulse-NMR. The data demonstrates that the melting profile of the sample could be greatly manipulated over a relatively narrow range of cooling rates. Large increases in cooling rate increase the final SFC of the sample by approximately 6%. Doubling the cooling rate increases the hardness of the sample 50%. Variation of the cooling rate as a tool to modify physical functionality of the network was found to be effective only for cooling rates lower than 5 °C min?1.