Invited lecture:
ENTROPY-DRIVEN ENGINEERING OF THE YIELD STRESS OF FATS

The yield stress of a fat is one of the most direct indicators of the functionality of such materials. Here we show that addition of 1% (w/w) of selected surfactants to mixtures of fully hydrogenated soybean oil in liquid soybean oil causes a decrease in the entropy of melting of the fat. A decrease in the entropy of melting in indicative of a greater disorder within the crystalline solid. The addition of selected surfactants causes point defects in the nanocrystalline structure of the triglycerides, which in turn is reflected in lower melting temperatures and enthalpies. A universal linear relationship (r²=0.90) between the yield stress and the entropy of melting was determined. Since both the enthalpy of melting and temperature of melting can be estimated from molecular compositional data, this opens us the possibility of predicting the yield stress of a fat from TAG molecular species information. The most effective surfactants for this purpose will be discussed. Here we also show how Boltzmann's microscopy entropy law can be used to describe the increase in entropy of a TAG nanoplatelet, which in turn is responsible for changes in yield stress.