The invention relates to an apparatus for fast and homogeneously heating a liquid product to a heating temperature by means of resistive heating, the apparatus comprising at least two vertically mounted, longitudinal, heating chambers that are arranged in series. The invention further relates to a process for fast and homogeneously heating a liquid product to a heating temperature by means of resistive heating in such apparatus comprising (a) continuously supplying the liquid product to the first heating chamber in series and flowing the liquid product continuously through the at least two heating chambers； (b) continuously generating an electrical current through the liquid product flowing through the heating chambers by continuously applying an electrical potential over each heating chamber, wherein the direction of the current is continuously alternated with a frequency of at least 500 Hz, to obtain heated liquid product； and (c) continuously discharging heated liquid product from the last heating chamber in series, wherein the liquid product has an electrical conductivity of at least 0.03 S/m.La invención se refiere a un aparato para calentar de manera rápida y homogénea un producto líquido a una temperatura de calentamiento por medio de calentamiento resistivo, el aparato comprende al menos dos cámaras de calentamiento montadas verticalmente, longitudinales, que están acomodadas en serie. La invención además se refiere a un proceso para calentar de manera rápida y homogénea un producto líquido a una temperatura de calentamiento por medio de calentamiento resistivo en tal aparato, que comprende.: (a) suministrar continuamente el producto líquido a la primera cámara de calentamiento en serie y hacer fluir el producto líquido continuamente a través de al menos dos cámaras de calentamiento； (b) generar continuamente una corriente eléctrica a través del producto líquido que fluye a través de las cámaras de calentamiento al aplicar continuamente un potencial eléctric
