Exploring the impact of high temperatures on chocolate viscosity

Objective: The objective of this research is to determine the effects of holding chocolates at high temperatures on their viscosity and rheological properties. These changes may be caused by interactions between cocoa polyphenols and milk proteins.

Materials and Methods: Single origin chocolate from Guatemala at three different cacao percentages: 40% (Milk, MC), 50% (Sweet, SC), and 70% (Semisweet, dark, DC) was used in this research. The chocolate was held in a 60 °C water bath for various times, between 2 and 9 hours. These times were increased to 12-15 hours. Chocolate was held at 40 °C for 2 hours as a control. Casson viscosity and yield stress were measured at 40 °C in an oscillatory rheometer.

Results: The yield stress (Pa) of each chocolate increased over holding time, with MC increasing about 6 Pa, 50% chocolate increasing about 3 Pa, and 70% chocolate increasing about 1 Pa. The viscosity (Pa.s) of the SC had a slight decreasing trend, and varied between about 3 Pa.s and 4.5 Pa.s. The viscosity of the MC did not seem to increase between 2 and 9 hours at 60 °C, remaining around 1.5 Pa.s. However, it decreased from the control, which was about 2 Pa.s. The viscosity of the 70% chocolate increased by about 0.5 Pa.s.

Impact: This research will help to understand more about the interactions of proteins and polyphenols in chocolate, which will help to explain the behavior of chocolate in high temperature conditions.