Studies are lacking on the nonthermal pasteurization of liquid foods using UV irradiators that centrifugally form very thin films to overcome the problem of limited penetration depth of UV. Grapefruit juice inoculated with Escherichia coli or Saccharomyces cerevisiae was processed at the following conditions: UV dose 4.8-24 mJ/cm(2); treatment time 3.2 s, cylinder rotational speed 450-750 rpm, cylinder inclination angle 15-45 degrees, outlet temperature 11 degrees C, and flow rate 300 ml/min, and was stored for 35 days. Appropriate dilutions of the samples were pour plated with TSA and TSA + 3% NaCl for E. coli and Sabouraud dextrose agar (SDA) and SDA + 5% NaCl for S. cerevisiae. Nonthermal UV processing at 19 mJ/cm(2), 450 rpm and 15 degrees reduced E. coli in grapefruit juice by 5.1 log(10). A dose of 14 mJ/cm(2) reduced S. cerevisiae by 6.0 log(10). Inactivation increased linearly with increasing UV dose. The inactivations at 600 and 750 rpm were similar, and were better than at 450 rpm. The results at 30 degrees and 45 degrees were similar, and were better than at 15 degrees. The occurrence of sublethal injury in either microorganism was not detected. Storing UV processed grapefruit juice at 4 and 10 degrees C reduced the surviving E. coli to below 1 log(10) cfu/ml in 14 days. Processing UV juice reduced the population of S. cerevisiae to less than 1 log(10) cfu/ml where it remained for 35 days during refrigerated storage. These results suggest that grapefruit juice may be pasteurized using a nonthermal UV irradiator that centrifugally forms a thin film. Published by Elsevier Ltd.