Inactivation of Escherichia coli in orange juice using ozone

Abstract

This research investigated the efficacy of gaseous ozone for the inactivation of Escherichia coli ATCC 25922 and NCTC 12900 strains in orange juice. Orange juice inoculated with E. coli (10 6 CFU mL -1 ) as a challenge microorganism was treated with ozone at 75-78µg mL -1 for different time periods (0-18 min). The efficacy of ozone for inactivation of both strains of E. coli was evaluated as a function of different juice types: model orange juice, fresh unfiltered juice, juice without pulp, and juice filtered through 500m or 1mm sieves. Fast inactivation rates for total reduction of E. coli were achieved in model orange juice (60 seconds) and in juice with low pulp content (6 min). However, in unfiltered juice inactivation was achieved after 15-18 min. This indicated that juice organic matter interferes with antibacterial activity of gaseous ozone. The effect of prior acid (pH 5.0) exposure of E. coli strains on the inactivation efficacy of ozone treatment was also investigated. There was a strain effect observed, where prior acid exposure resulted in higher inactivation times in some cases by comparison with the control cells.However, the overarching influence on inactivation efficacy of ozone was related to the pulp content. Generally, the applied gaseous ozone treatment of orange juice resulted in a population reduction of 5 log cycles.Key words: Escherichia coli, ozone, non-thermal inactivation, acid exposure, orange juice, microbial kinetics Industrial relevance: To facilitate the preservation of unstable nutrients many juice processors have investigated alternatives to thermal pasteurisation, including unpasteurised short shelf life juices with high retail value. This trend has continued within the European Union. However within the US recent regulations by the FDA have 3 required processors to achieve a 5-log reduction in the numbers of the most resistant pathogens in their finished products. Pathogenic E. coli may survive in acid environments such as fruit juices for long periods. This study demonstrates that the use of ozone as a non-thermal technology is effective for inactivation of E. coli and acid exposed E. coli in orange juice. Information on the design of the ozone treatment for inactivation of E. coli which results into safe juice products is also among the main outputs of this work. Ozone auto-decomposition makes this technology safe for fruit juice processing.4

A novel ozone gas sensor based on one-dimensional (1D) α-Ag2WO4 nanostructures

“…29,[34][35][36][37][38][39] For example, ozone has been employed as a powerful drinking-water disinfectant and oxidant. 34,35,40 On the other hand, when the ozone level in an atmosphere exceeds a certain threshold value, the exposure to this gas becomes hazardous to human health and can cause serious health problems (e.g.…”

Ozone inactivation of acid stressed Listeria monocytogenes and Listeria innocua in orange juice using a bubble column

“…The fresh orange juice was then submitted to a finishing process by passing through a sieve (Laboratory test sieve, Retsch, Germany) of 1 mm diameter (mesh no. 18) to reduce the pulp content (Patil, Bourke, Frias, Tiwari, & Cullen, 2009). All juice preparations were stored at 4 C. The pH was measured using a pH meter with a glass electrode (Orion Model, England) and was found to be in the range of 3.5e3.7.…”

Inactivation kinetics and growth dynamics during cold storage of Escherichia coli ATCC 11229, Listeria innocua ATCC 33090 and Saccharomyces cerevisiae KE162 in peach juice using aqueous ozone

“…The FDA's approval of ozone as a direct additive to food in 2001 led to the application of ozone for processing of various fruit juices, including apple cider (Steenstrup & Floros, 2004), apple juice (Choi et al, 2012;Patil, Valdramidis, Tiwari, Cullen & Bourke, 2011;Patil et al, 2010a), orange juice (Patil, Bourke, Frías, Tiwari & Cullen, 2009;Patil, Valdramidis, Cullen, Frias & Bourke, 2010b;Tiwari, Muthukumarappan, O'Donnell & Cullen, 2008a,b), blackberry juice (Tiwari, O'Donnell, Brunton & Cullen, 2009a) and tomato juice (Tiwari, O'Donnell, Brunton and Cullen, 2009a). Regarding apple juice and cider, guidance for industry was issued by the FDA (United States Food, Administration Drug & USFDA., 2004) establishing processing and compositional factors needed to be controlled to ensure the efficacy of the ozonation process.…”