Ohmic heating processing in dulce de leche: Physical and thermal profile, microstructure, and modeling of crystal size growth

The effect of ohmic heating (OH) parameters (voltage gradient, 2, 4, 6, 8, and 10 V cm-1) on the quality properties of dulce de leche (DL) was evaluated. Optical (L*, C*, and BI), rheological (flow curves and oscillatory tests) and thermal (differential scanning calorimetry) parameters as well as microstructure (optical microscopy) and modeling of the crystal size growth were evaluated during the storage time (60 days at 25oC). Overall, OH processing resulted in lower optical (C* and BI) parameters, indicating a product with a lower intensity of caramel brown color. For the rheological assays, it was observed a decrease in the viscosity and consistency of the products (lower k values and higher n and G’ values). Finally, the OH-treated products presented higher numbers of lactose crystals of smaller size. The impact of OH was dependent on the voltage gradient, with a more pronounced effect on the product submitted to high electric field (10 V cm-1). Overall, OH is an interesting technology to be used in DL processing, being recommended the utilization of 8 V cm-1 of voltage gradient due to the better-quality properties.