Use of High-Intensity Ultrasound and UV-C Light to Inactivate Some Microorganisms in Fruit Juices

Abstract

Novel technologies that involve non-thermal processes have been investigated in the last two decades as full or partial alternatives to conventional heat treatment. The main objective of this study was to evaluate the survival of single or strain cocktail of Escherichia coli, Saccharomyces cerevisiae, and a yeast cocktail in orange (pH 3.5; 9°Brix) and/or apple (pH 3.1; 12°Brix) juices and in 0.1% w/w peptone water processed by two non-thermal techniques: high-intensity ultrasound (USc) and/or short-wave ultraviolet radiation (UV-C). USc treatments (20 kHz, 95 µm-wave amplitude) were performed using a stainless steel continuous flow cell with a 13-mm probe (0.2 L/min; 40°C). The UV-C device consisted of a 90-cm long UV-C-lamp (100 W) placed inside a glass tube leaving an annular flow space (0.2 L/min; 40°C). Inoculated systems were recirculated through simultaneous or consecutive USc and UV-C devices and samples were taken at preset time intervals. Microbial populations were monitored by plate count technique. In peptone water and apple juice, UV-C radiation provoked higher E. coli ATCC 35218 inactivation than USc treatment. E. coli ATCC 35218 and its cocktail were more sensitive than S. cerevisiae KE162 and the cocktail of yeasts. UV-C efficiency was highly dependent on media nature. The poor single effect of UV-C light in orange juice was enhanced by the combination with USc. Combined treatment was more effective in simultaneous rather than in a series of USc−UV-C arrangement.

Inactivation of Salmonella enterica by UV-C Light Alone and in Combination with Mild Temperatures

“…2 and Table 3). The difficulty of UV light treatment in achieving a 5 log 10 reduction due to the low penetration capacity of UV photons on liquid foods has prompted several authors to develop hurdle strategies combining UV light with other novel processing techniques or milder conventional preservation methods (3,49). The combination of heat at sublethal temperatures with other nonthermal technologies such as high hydrostatic pressure (HHP), US, and PEF at low intensity results in an equivalent or even higher degree of microbial inactivation (38,39).…”

Study of the inactivation of spoilage microorganisms in apple juice by pulsed light and ultrasound

“…1b). Char et al (2010) obtained a 1-log reduction for S. cerevisiae in orange juice (pH 3.4, 10 Brix) after 20 min of sonication (20 kHz, 80% amplitude, 500 mL) at 40 ± 1 C. While in this study (US: 20 kHz, 80% amplitude, 100 mL) 1.5 and 2.4 log cycles of reduction were obtained for the same treatment time and 44 C in commercial apple juice and natural squeezed apple juice, respectively. The use of a smaller container which improves the sonication process (Guerrero et al, 2001) and a different matrix could be responsible for the greater inactivation observed in this study under the same US conditions.…”

Modeling optimal process conditions for UV-heat inactivation of foodborne pathogens in liquid foods

“…Another alternative is to develop "hurdle" approaches combining UV radiation with other non-thermal technologies or conventional preservation methods at moderate intensity (Char et al, 2010;Walkling-Ribeiro et al, 2008). One of the most promising hurdle strategies is the combination of UV-C radiation with mild heat (UV-H treatment), since UV inactivation increases at temperatures between 45 C and 60 C (Gay an et al, 2011;Geveke, 2008).…”