Influence of Modified Soybean Lecithins on Chocolate Crystallization
Theo Guenter Kieckbusch, Eriksen Koji Miyasaki, Valdecir Luccas, 
School of Chemical Engineering (FEQ), University of Campinas
Cereal-Chocotec, Food Technology Institute (ITAL)
Campinas, Brazil

The influence of two types of modified soybean lecithins (hydroxylated and enzymatically hydrolyzed) at different concentrations (0.1%; 0.2% and 0.3% (w/w)), fixing the PGPR's concentration in 0.2% on the static Isothermal crystallization patterns of dark chocolate mass was evaluated. The results were compared to chocolate samples containing standard soybean lecithin (and PGPR), chocolate without lecithin (only PGPR), chocolate without any emulsifiers (chocolate mass) and plain cocoa liquor. The isothermal crystallization curves at 15 °C were obtained after samples melting at 60oC for 1 hour before starting the readings, using a BRUKER Nuclear Magnetic Resonance (NMR) device and the direct method. The induction time, ζ, and the equilibrium Solid Fat Content, SFCmax were retrieved from the curves. Avrami’s equation parameters n and k were obtained by least-squares nonlinear regression. The parameter half-life of crystallization (t1/2) was calculated using Avrami’s parameters. The values of Avrami’s n parameter of all samples studied felt in the range between 1.43 and 1.60, suggesting similarity in the types of crystals formed and of the growth mechanisms. A clear difference in k values was only observed for the cocoa liquor sample. Only cocoa liquor and the 0.3% hydroxylated lecithin sample showed significant differences compared to chocolate mass sample without any emulsifier and to chocolate without lecithin. The parameter k of the 0.2% PGPR sample showed no significant differences compared to the plain chocolate mass sample, confirming that PGPR does not affect the static crystallization process. No significant differences in induction times were found among all the samples of chocolates. ζ values varied between 8.0 and 9.0 min. except for cocoa liquor (ζ ~ 5.0 min). Higher values of the half- life of crystallization (t1/2) were found at high lecithin concentrations, except to the hydroxylated lecithin samples. The 0.2% PGPR and chocolate mass samples did not show statistical difference. SFCmax values ranged from 70-73%, showing lower values with increasing emulsifier concentrations. The cocoa liquor sample scored the highest k, but not the lowest t1/2 value, not even the highest value of SFCmax, suggesting the existence of a different mechanism or specific factors modulating its crystallization.