title: UV Tolerance of Spoilage Microorganisms and Acid-Shocked and Acid-Adapted Escherichia coli in Apple Juice Treated with a Commercial UV Juice-Processing Unit.
abstract: The enhanced thermal tolerance and survival responses of Escherichia coli O157:H7 in acid and acidified foods is a major safety concern for the production of low-pH products, including beverages. Little is known about this phenomenon when using UV light treatments. This study was conducted to evaluate the effects of strain (E. coli O157:H7 strains C7927, ATCC 35150, ATCC 43895, and ATCC 43889 and E. coli ATCC 25922) and physiological state (control-unadapted, acid adapted, and acid shocked) on the UV tolerance of E. coli in apple juice treated under conditions stipulated in current U.S. Food and Drug Administration regulations. A greater than 5-log reduction of E. coli was obtained under all tested conditions. A significant effect of strain (P < 0.05) was observed, but the physiological state did not influence pathogen inactivation (P ≥ 0.05). The UV sensitivity of three spoilage microorganisms (Aspergillus niger, Penicillium commune, and Alicyclobacillus acidoterrestris) was also determined at UV doses of 0 to 98 mJ/cm(2). Alicyclobacillus was the most UV sensitive, followed by Penicillium and Aspergillus. Because of the nonsignificant differences in UV sensitivity of E. coli in different physiological states, the use of an unadapted inoculum would be adequate to conduct challenge studies with the commercial UV unit used in this study at a UV dose of 14 mJ/cm(2). The high UV tolerance of spoilage microorganisms supports the need to use a hurdle approach (e.g., coupling of refrigeration, preservatives, and/or other technologies) to extend the shelf life of UV-treated beverages.
authors.affiliation: Centro Nacional de Ciencia y Tecnoloǵıa de Alimentos, Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio, Ćodigo postal 11501-2060, San Jośe, Costa Rica. jessie.usaga@ucr.ac.cr.
authors.forename: Jessie
authors.initials: J
authors.lastname: Usaga
authors.affiliation: Department of Food Science, Cornell University, 630 W. North Street, Geneva, New York 14456, USA.
authors.forename: Olga I
authors.initials: OI
authors.lastname: Padilla-Zakour
authors.affiliation: Department of Food Science, Cornell University, 630 W. North Street, Geneva, New York 14456, USA.
authors.forename: Randy W
authors.initials: RW
authors.lastname: Worobo
mesh_terms: D000143:Acids / Q000378:metabolism; D056450:Alicyclobacillus / Q000254:growth & development / Q000528:radiation effects*; D001234:Aspergillus niger / Q000254:growth & development / Q000528:radiation effects*; D001628:Beverages / Q000191:economics / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects*; D005506:Food Contamination / Q000032:analysis; D005514:Food Irradiation; D027845:Malus / Q000737:chemistry / Q000382:microbiology*; D010407:Penicillium / Q000254:growth & development / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014481:United States
chemical_list: D000143:Acids