Influence of high pressure processing on populations of Salmonella enterica in fresh green-mature tomato fruits and subsequent ripening.
Ocampo-Garcia, Nora Fabiola
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The objective of this work was to determine the effect of high pressure processing (HPP) on fresh tomato-associated outbreak isolates of Salmonella enterica in broth and on green mature tomato fruits. Nalidixic acid resistant (to 50 ppm) cultures of Salmonella enterica ser. Newport and Salmonella enterica ser. Braenderup were suspended in tryptic soy broth to a concentration of approximately 8 log CFU/ml and subjected to 350, 450, and 550 MPa for 120 s. Samples were serially diluted in peptone water, and surface plated onto tryptic soy agar supplemented with nalidixic acid (50 ppm; TSAN) and incubated at 35Â°C for 48 h. Reductions of 5.64, 6.30, and 6.61 log CFU/ml in S. Newport, and reductions of 4.10, 5.22, and 6.35 log CFU/ml in S. Braenderup at 350, 450, and 550 MPa, respectively, were observed. Green tomato fruits inoculated with S. Newport or S. Braenderup to an initial concentration of approximately 6 log CFU/g were sealed in a bag containing 350 ml of 1% CaCl2 and subjected to the same pressure treatments described above. The whole tomato fruits were pummeled in a stomacher and samples were surface plated onto TSAN supplemented with 1% pyruvic acid. Reductions of 1.55, 2.89, and 4.26 log CFU/g for S. Newport and 1.22, 2.26, and 3.77 log CFU/g for S. Braenderup at 350, 450, and 550 MPa, respectively, were observed. Bagged (350 ml 1% CaCl2) samples of non-inoculated green tomato fruits were subjected to the same conditions described above. HPP treated tomatoes were then subjected to an ethylene gas (125 ppm; 0.7 cc/min) for 5 to 6 days. Pressured tomato fruits did not ripen. Even though HPP effectively reduced populations of S. enterica, it adversely affects the ripening characteristics of green mature tomato fruits.
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