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

© 2015 Elsevier Ltd. 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 300MPa 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.