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The bactericidal efficacy of UV treatments to fruit juices is limited because of their low UV transmittance; therefore it is necessary to design combined processes to improve their lethality. This investigation was carried out to determinate the lethal effect of UV-C treatments at mild temperatures (UV-H treatments) on the UV-resistant Escherichia coli strain STCC 4201 suspended in apple juice. A synergistic effect was observed and the optimum temperature for the combined process was established.Subsequently the effect of the optimized treatment on the lethality of a E. coli cocktail (STCC 4201, STCC 471, ATCC 27325, ATCC 25922, and O157:H7 Chapman strain) and on freshly squeezed apple juice quality were evaluated.A UV treatment of 20.33 J/mL reached 0.61±0.01, 0.83±0.07, 1.38±0.04, 1.97±0.06, 3.72±0.14, 5.67±0.61, and more than 6 Log10 cycles of inactivation at 25.0, 40.0, 50.0, 52.5, 55.0, 57.5, and 60.0 ºC, respectively. The optimum conditions for exploiting the synergistic effects were UV doses of 27.10 J/mL, temperature of 55.0 ºC, and 3.58 minutes of treatment time. This treatment guaranteed more of 5 Log 10 reductions of the cocktail of five strains of E. coli without affecting pH, ºBrix, and acidity of freshly squeezed apple juice. The UV-H treatment did not increase the loss of ascorbic acid compared to the same UV treatment at room temperature, but approximately doubled the inactivation of polifenoloxidase.

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