Survival of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice as affected by ozone and treatment temperature.
Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone was evaluated. A five-strain mixture of E. coli O157:H7 or a five-serovar mixture of Salmonella was inoculated (7 log CFU/ml) into apple cider and orange juice. Ozone (0.9 g/h) was pumped into juices maintained at 4 degrees C, ambient temperature (approximately 20 degrees C), and 50 degrees C for up to 240 min, depending on organism, juice, and treatment temperature. Samples were withdrawn, diluted in 0.1% peptone water, and surface plated onto recovery media. Recovery of E. coli O157:H7 was compared on tryptic soy agar (TSA), sorbitol MacConkey agar, hemorrhagic coli agar, and modified eosin methylene blue agar; recovery of Salmonella was compared on TSA, bismuth sulfite agar, and xylose lysine tergitol 4 (XLT4) agar. After treatment at 50 degrees C, E. coli O157:H7 populations were undetectable (limit of 1.0 log CFU/ml; a minimum 6.0-log CFU/ml reduction) after 45 min in apple cider and 75 min in orange juice. At 50 degrees C, Salmonella was reduced by 4.8 log CFU/ml (apple cider) and was undetectable in orange juice after 15 min. E. coli O157:H7 at 4 degrees C was reduced by 4.8 log CFU/ml in apple cider and by 5.4 log CFU/ml in orange juice. Salmonella was reduced by 4.5 log CFU/ml (apple cider) and 4.2 log CFU/ml (orange juice) at 4 degrees C. Treatment at ambient temperature resulted in population reductions of less than 5.0 log CFU/ml. Recovery of E. coli O157:H7 and Salmonella on selective media was substantially lower than recovery on TSA, indicating development of sublethal injury. Ozone treatment of apple cider and orange juice at 4 degrees C or in combination with mild heating (50 degrees C) may provide an alternative to thermal pasteurization for reduction of E. coli O157:H7 and Salmonella in apple cider and orange juice.
Williams
Robert C
RC
Department of Food Science and Technology, The University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
Sumner
Susan S
SS
Golden
David A
DA
D001628:Beverages / Q000382:microbiology*; D032084:Citrus sinensis / Q000382:microbiology; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development*; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D027845:Malus / Q000382:microbiology; D010126:Ozone / Q000494:pharmacology*; D012475:Salmonella / Q000254:growth & development*; D013696:Temperature; D013997:Time Factors
D010126:Ozone