Effects of Glycerol and Tween 60 on the Crystallization Behavior, Mechanical Properties, and Microstructure of a Plastic Fat

The addition of 0.10% glycerol or Tween 60 increased the yield force of a 70:30 (w/w) mixture of triolein/HMF (high-melting fraction of milkfat) at 5 °C. Further increases in glycerol or Tween 60 caused a decrease in yield force. Solid fat content (SFC) versus time profiles at 30 °C (glycerol) and 28 °C (Tween 60) allowed for the determination of Avrami rate constants of crystallization ( k ) and Avrami exponents ( n ). Higher Avrami constants and lower Avrami indices (higher rate of crystal growth), smaller crystallites, and a shorter induction time of nucleation were observed in samples containing 0.10% Tween 60 relative to the control and 0.50% Tween 60. A 0.10% glycerol addition, on the other hand, yielded opposite results. The increase in hardness induced by small additions of Tween 60 could be attributed to decreases in crystallite size at constant SFC and fractal dimension. The increase in hardness induced by small additions of glycerol could only be attributed to increases in the crystal-melt interfacial tension, at constant SFC and fractal dimension, despite increases in crystallite size.