Traditional thermal techniques may cause losses in nutritional quality and phytochemical contents, and also in physicochemical, rheological, and organoleptic properties of processed fruit juices. This paper provides an overview of the effect on these qualities by the use of alternatives to traditional thermal treatments in fruit-juice processing, for three key operations in fruit-juice production such as microbial inactivation, enzyme inactivation, and juice-yield improvement. These alternatives are UV light, high-intensity light pulses, -irradiation, pulsed electric fields, radiofrequency electric fields, Ohmic heating, microwave heating, ultrasound, high hydrostatic pressure, supercritical carbon dioxide, ozonation, and flash-vacuum expansion. Although alternatives to heat treatments seem to be less detrimental than the thermal treatment, there are many parameters and conditions that influence the output, as well as the nature of the juice itself, hampering comparisons between different studies. Additionally, future research should focus on understanding the mechanisms underlying the changes in the overall quality of fruit juices, and also on scaled-up processes, process design, and optimization that need to be deal with in detail to maximize their potential as alternative nonthermal technologies in fruit-juice processing while maintaining fruit-juice attributes to the maximum.
