Inactivation of E. coli and S. cerevisiae in fruit juices processed by non-thermal emerging technologies

CHAR, C D; MYTILANIKI, E; GUERRERO, S N; ALZAMORA, STELLA MARIS

Iguassu Falls City

Conferencia; International Conference of Agricultural Engineering; 2008

Novel technologies that involve non-thermal processes have being investigated in  the two last decades as full or partial alternatives to conventional heat treatment. The main objective of this study was to evaluate the survival of single or pooled Escherichia coli and Saccharomycescerevisiae in orange (pH: 3.5; 9 ºBrix) and apple (pH: 3.1; 12 ºBrix) juices and in a model system (0.1% peptone water) processed by two non thermal techniques: continuous flow high intensity ultrasound (USc) and/or short wave ultraviolet radiation (UV-C). USc treatments (20 kHz, 95 µm-wave amplitude) were performed using a USc cell  with a 13 mm probe (40ºC). The UV-C device consisted of a 90 cm long UV-C-lamp (100 W) placed inside a glass tube leaving an annular space ~ 0.2 mm (28ºC). Inoculated systems were recirculated and samples were taken at preset time intervals. Microbial populations were monitored by plate count technique. In model system and apple juice, UV-C treatment provoked higher E. coli  inactivation than USc treatment. E. coli and its pool were more sensitive than S. cerevisiae and the pool of yeasts. UV-C efficiency was very dependent on media nature. However, 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 successive USc-UV-C treatment.