Improving the efficiency of ultra-high pressure homogenization treatments to inactivate spores of Alicyclobacillus spp. in orange juice controlling the inlet temperature

•We evaluate inlet temperature on UHPH inactivation of Alicyclobacillus spores.•Increasing inlet temperature of orange juice increases UHPH inactivation of spores.•Lethal effect of UHPH treatments is mainly due to the thermal effect caused.•Inlet temperatures above 70 °C are required to inactivate at least 105 spores/ml.

Samples of orange juice inoculated with strain CECT 7094 of Alicyclobacillus acidoterrestris or strain CECT 5324 of Alicyclobacillus hesperidum were pre-heated to five different temperatures (20, 50, 60, 70 and 80 °C) before applying a 300 MPa Ultra High Pressure Homogenization (UHPH) treatment. Treated and control samples were kept during 30 days at 22 °C, 30 °C and 43 °C to evaluate the ability of the surviving spores to germinate and grow. UHPH treatments hardly affected the spore counts at the lowest inlet temperature (20 °C), but significant reductions were observed when inlet temperature raised to 60 °C, achieving lethality values above 5 Log CFU/ml when juice samples were pre-heated at 70 for A. hesperidum and 80 °C for A. acidoterrestris. During the later storage of the juice samples Alicyclobacillus counts increased significantly during the first 15 days in samples pre-heated at 20 °C and 50 °C when they were stored at both 30 °C and 43 °C, achieving similar counts than control samples, but not at 22 °C. Nevertheless, in samples pre-heated at 70 and 80 °C spore counts remained below the detection limit indicating that these treatments were the most efficient inactivating Alicyclobacillus spp. spores.