These results indicate great potential for the use of Pulsed Light (PL) for the effective reduction of E. coli in apple juice and cider without using heat, particularly when the treatment is performed in a thin layer, turbulent flow configuration. The levels of inactivation reported in the current study were achieved in less than four seconds, which highly recommends this process for in-line applications, with minimal modifications of existing processing lines.
impact statement issue
Apple cider can be a vehicle for foodborne illnesses generated by E. coli O157:H7. In order to prevent foodborne outbreaks associated with cider, the Food and Drug Administration (FDA) requires that processors achieve a 5 log reduction of the most resistant pathogens in apple cider. Due to consumers' preference for non-pasteurized cider, processors are seeking alternative methods to render apple cider safe for consumption. Pulsed Light (PL) treatment is a FDA-approved nonthermal technology that consists of short and intense pulses of light in the UV-NIR range. PL treatment is capable of inactivating a wide range of microorganisms, both in liquid substrates and at the surface of solid substrates. The use of PL has the potential to eliminate the need for chemicals, irradiation, or heat treatment. Due to its flexible design and scalability, PL could become a relatively inexpensive solution for small or medium size companies.
impact statement response
The objective of our work was to examine the potential of Pulsed Light treatment to achieve more than 5 log reduction of E. coli in apple cider and apple juice. Nonpathogenic E. coli ATCC 25922 and pathogenic E. coli O157:H7 cells were incubated overnight in BPB and suspended in apple cider and juice, then exposed to PL at fluence levels of up to 13.1 J/cm², in a Xenon RS-3000C PL unit. The PL treatments were performed both in static mode and under turbulence. In the static treatments inactivation levels of E. coli O157:H7 in apple cider and apple juice of up to 2.52 ± 0.19 log CFU and 3.22 ± 0.29 log CFU, respectively. The treatments under turbulence led to maximum reduction of 5.76 ± 0.06 log CFU in cider and 7.15 ± 0.22 log CFU reduction in apple juice. These results indicate that turbulence can drastically enhance the level of microbial kill in PL treatment, facilitating the achievement of the required 5-log reduction of E. coli O157:H7 in apple juice and cider without heating. No noticeable effects of the PL treatment on the treated juice and cider were observed, but future work will have to evaluate the effects of the treatment on the sensory properties of juice and cider. This will help juice processors make a decision regarding the adoption of PL treatment as an alternative to heat treatment or the currently used static UV treatment.
impact statement summary
Pulsed Light (PL) treatment is an emerging nonthermal treatment that has been shown to induce cell injury and death of a wide range of microorganisms. We have tested the ability of PL to inactivate microorganisms in apple cider and apple juice. Apple cider and apple juice were inoculated with both nonpathogenic E. coli ATCC 25922 and pathogenic E. coli O157:H7. The inoculated samples were subjected to PL treatments at fluence levels of up to 13.1 J/cm², both in static mode and under turbulence. The static treatments resulted in inactivation levels in apple cider and juice of up to 2.52 ± 0.19 log CFU and 3.22 ± 0.29 log CFU, respectively. The treatments performed under turbulence led to a reduction of 5.76 ± 0.06 log CFU in cider, at a fluence higher than 11.7 J/cm², and a reduction of 7.15 ± 0.22 log CFU in apple juice, at a fluence higher than 8.8 J/cm². These results indicate that Pulsed Light treatments performed under turbulent conditions turbulence allow the achievement of the FDA required 5 log reduction of E. coli O157:H7 in apple juice and apple cider, without heating.
