Inactivation study of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris and Aspergillus niger spores under Ultra-High Pressure Homogenization, UV-C light and their combination

摘要

Lethality rates of Bacillus subtilis, Geobacillus stearothertnophilus, Alicyclobacillus acidoterrestris, and Aspergillus niger spores were studied into phosphate-buffer saline (PBS) and PBS supplemented with caramel (PBSC) after Ultra-High Pressure Homogenization (UHPH) and UV-C treatments applied separately and combined. UHPH procedures were carried out at different pressures (100, 200 and 300 MPa) and inlet temperatures (20, 50 and 70 degrees C), while UV-C treatments consisted in a combination of doses (from 0.9 to 21.5 J/mL) and eventually temperatures (20 and 50 degrees C) or cycles. UHPH treatments were efficient at inactivating A. niger conidiospores in PBS but much less efficient in the inactivation of bacterial spores. Efficacy of UHPH against bacterial spores was increased pre-heating the samples at 70 degrees C. UV-C was more efficient against bacterial spores in PBS, but much less in PBSC. When UV-C treatments were applied through several cycles their efficacy against B. subtilis spores increased. Combination of UHPH at 200 MPa and UV-C moderately increased the lethal effect on B. subtilis spores than when these treatments were applied separately. Nevertheless, the combination of both technologies has a complementary effect allowing acting on a wide range of microorganisms, increasing the possibilities to obtain a safer and durable product.