ADVANTAGES OF USING OHMIC HEATING IN DULCE DE LECHE MANUFACTURING

Ohmic heating (OH, 0, 2, 4, 6, 8, or 10 V cm-1, 72 °C/15 s, 60 Hz) at Dulce de leche processing was investigated. The equipment consisted in an ohmic heating chamber, and rectangular 316 stainless steel electrodes positioned 10 cm apart. Both OH and conventional heat treatment was performed using the same temperature (72 °C) and holding time (15 s), and the milk was rapidly cooled (< 30 ° C) in an ice bath after processing. The samples were submitted to The gross composition (moisture, protein, ash, lipids, and carbohydrates), Hydroxymethylfurfural (HMF) values, fatty acid profile, volatile compounds and Water Mobility by Time-domain nuclear magnetic resonance (TD-NMR); in addition the thermal profile and energy consumption was also performed.OH-treated milk resulted in improvements in the quality parameters of Dulce de leche, with a decrease in energy expenditure (69.85-141.86 vs 1260 kJ) and hydroxymethylfurfural (HMF) levels (7.64-8.54 vs 9.53 µmol L-1) and formation of volatile compounds important for the sweetness of Dulce de leche (butanoic acid and 2-furan methanol). In addition, the gross composition, fatty acid profile (atherogenic, thrombogenic, desired fatty acids, and hypercholesterolemic saturated fatty acids) do not present relevant change. TD-NMR proportionated the existence of three relaxation environments, with OH presenting more homogeneous domain, suggesting compact systems. In particular, the use of higher electric field (> 6 V cm-1) led to a 14-78% decrease in process time, and improved volatiles profiling, besides decrease the energy expenditure (69.85-141.86 vs 1260 kJ, p>0.05) and the time required to reach the process temperature (360, 310, and 90 s against 420 s, respectively, p>0.05) and the thermal load (15.57-34.38 against of 21.29 s). OH has proven to be a suitable technology for milk treatment, resulting in improvements in the quality parameters of Dulce de leche with positive impact at the process time and energy expenditure