Several outbreaks of foodborne poisoning have been associated with consumption of unpasteurized fruit juices, despite their low pH and high organic acids content, and contamination of unpasteurized apple and citrus juices with Escherichia coli O157:H7 has been reported.

In the USA and other countries, guidelines require fruit juice processing to be subject to hazard analysis and critical control point (HACCP) programmes, including a 5-log unit reduction in counts of target microorganisms. Single-strength juices such as lemon and lime juices can be produced from concentrates which are generally heated to destroy vegetative pathogens. However, during storage, transportation and reconstitution of the concentrates to single strength, there is potential for contamination of the juice by pathogenic bacteria.

Previous studies have suggested that E. coli O157:H7 and other pathogenic bacteria are inactivated in lemon, lime and cranberry juice concentrates. Intrinsic antimicrobial properties of these juices, such as low pH, high titratable acidity and the presence of antimicrobial compounds, may be responsible for this effect. Therefore, these factors could be used as hurdles to inactivate pathogens in foods.

Enache et al.¹ investigated the inactivation of a mix of 5 strains of E. coli O157:H7 in reconstituted single-strength lemon and lime juices and commercially produced shelf-stable lemon and lime juices. Survival of stationary phase and acid-adapted E. coli was evaluated at room temperature (22°C). The juices contained no preservatives, and had pH values of 2.5-2.6 and titratable acidities of 4.51-4.53%. A >5-log unit reduction in the stationary cells count was obtained in both lemon and lime juices after 72 hours of incubation, with lemon juice having a significantly higher inhibitory effect than lime juice. It is concluded that storage of these juices at room temperature for three days may be a viable alternative to pasteurization.
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1 Enache, E; Chen, Y; Elliott, PH (2009). Inactivation of Escherichia coli O157:H7 in single-strength lemon and lime juices. Journal of Food Protection 72 (2) 235-240.

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