Non-pasteurized orange juice is manufactured by squeezing juice from fruit without peel removal. Fruit surfaces may carry pathogenic microorganisms that can contaminate squeezed juice.

Titanium dioxide–UVC photocatalysis (TUVP), a non-thermal technique capable of microbial inactivation via generation of hydroxyl radicals, was used to decontaminate orange surfaces. Levels of spot-inoculated Escherichia coli O157:H7 (initial level of 7.0 log CFU/cm2) on oranges (12 cm2) were reduced by 4.3 log CFU/ml when treated with TUVP (17.2 mW/cm2). Reductions of 1.5, 3.9, and 3.6 log CFU/ml were achieved using tap water, chlorine (200 ppm), and UVC alone (23.7 mW/cm2), respectively. E. coli O157:H7 in juice from TUVP (17.2 mW/cm2)–treated oranges was reduced by 1.7 log CFU/ml.

After orange juice was treated with high hydrostatic pressure (HHP) at 400 MPa for 1 min without any prior fruit surface disinfection, the level of E. coli O157:H7 was reduced by 2.4 log CFU/ml. However, the E. coli O157:H7 level in juice was reduced by 4.7 log CFU/ml (to lower than the detection limit) when TUVP treatment of oranges was followed by HHP treatment of juice, indicating a synergistic inactivation effect.

The inactivation kinetics of E. coli O157:H7 on orange surfaces followed a biphasic model. HHP treatment did not affect the pH, °Brix, or color of juice. However, the ascorbic acid concentration and pectinmethylesterase activity were reduced by 35.1 and 34.7%, respectively.

 Inactivation of Escherichia coli O157:H7 on orange fruit surfaces and in juice using photocatalysis and high hydrostatic pressure

Journal of Food Protection®, Number 6, June 2015, pp. 1064-1243, pp. 1098-1105(8), DOI: http://dx.doi.org/10.4315/0362-028X.JFP-14-522

Yoo, Sungyul; Ghafoor, Kashif; Kim, Jeong Un; Kim, Sanghun; Jung, Bora; Lee, Dong-Un; Park, Jiyong

http://www.ingentaconnect.com/content/iafp/jfp/2015/00000078/00000006/art00005