Characterizing Maillard reaction kinetics and rheological changes in white chocolate over extended heating

Abstract

Molten white chocolate held at high temperatures for extended periods of time undergoes thickening and nonenzymatic browning reactions. Lactose and milk proteins participate in Maillard browning, which occurs more rapidly at higher temperatures. Crystallization of amorphous lactose and high temperature contribute to rheological changes over heating. In the present study, five white chocolates of varied compositions were sampled over time at different temperatures. White chocolates containing amorphous lactose showed increases in complex viscosity, while chocolates with crystalline or no lactose showed no change in rheological properties. Maillard browning was measured through both colorimetry and spectrophotometric analysis of brown pigments. Both markers showed the greatest browning for Nonfat dry milk (NFDM)—containing systems. Chocolates containing no NFDM (milk protein isolate, MPI, or crystalline lactose) showed no change in absorbance after clarification, but some browning in colorimetry results, likely due to residual amorphous lactose in the MPI or increased mobility of lactose from crystals at high temperatures. The evolution of fluorescent intermediates was visualized using fluorescence spectroscopy, revealing that these intermediates were formed prior to colored end stage products and were consumed as the reaction approaches completion. An excess of lactose in the system meant reducing sugar declines were relatively small throughout. Kinetic models were created to determine the influence of chocolate composition and temperature on thickening as related to complex viscosity (first order) and browning via colorimetry and absorbance (pseudo‐zero order). Both thickening rate and Maillard reaction rates were faster in chocolates with greater levels of amorphous lactose and when held at higher temperatures. Practical Application So‐called “golden chocolate” is white chocolate that has been held at warm temperatures for a period of time to undergo Maillard browning. However, thickening of the chocolate during heating can cause processing problems. In this study, viscosity changes are correlated with Maillard browning kinetics to help chocolate manufacturers find optimal conditions for creating new products.

Effect of Heat Treatment on Nutritional and Chromatic Properties of Mung Bean (Vigna radiata L.)

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“…In the case of extended heating of chocolate, Maillard browning also changes the product's viscosity (Rodier and Hartel, 2021).…”

Improving flushing processes through targeted control of the temperature boundary conditions

“…An apparent viscosity can be described for any given shear rate. Several studies have shown that the viscosity of liquid chocolate strongly depends on the particle size distribution of the solid particles within the continuous phase [6], the manufacturing process [7], the ingredients, for example, milk powder type [8,9], the chocolate type [10] and the temperature [7,11]. Other studies were conducted to determine a suitable model to describe the resulting shear stress as a function of the strain rate [10,12,13].…”