IAFP 2009 Program Book and Abstract Book - AB53

reduction for S. aureus at 330MPa. There was no survival of either organism at 600MP though microorganisms grown as biofilms were more resistant than their planktonic counterparts. A number of pouches showed microbial growth at pressures up to 500MPa. One pouch contained the same riboprint as the test suspension whilst the other ‘spoilage’ microorganisms were identified as typical skin flora. Significance: A potential risk of leaker spoilage for HP processed products was demonstrated, which can be controlled by minimizing contamination in the HP units and via more hygienic pack handling. T7-10 Inactivation of Bacterial Spores in Tomato Sauce by High Hydrostatic Pressure DSC ANNE VERCAMMEN, B. Vivijs, M. Hendrickx and C. W. Michiels Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Dept. of Microbial and Molecular Systems, B-3001 Heverlee, Belgium Introduction: Bacterial spore formers, like Alicyclobacillus acidoterrestris and Bacillus coagulans, can cause flat-sour type of spoilage in heat-processed tomato products. B. coagulans is moderately acidophilic, being able to grow down to a pH of about 4.0, while A. acidoterrestris can even grow at a pH as low as 2.5. Since the spores of both organisms are both heat and acid resistant, they can survive the commercial heating processes applied to tomato products. Purpose: The objective of this work was to study the germination and inactivation of A. acidoterrestris and B. coagulans spores in tomato sauce by high hydrostatic pressure treatment at temperatures up to 60°C. Methods: Spore suspensions of A. acidoterrestris ATCC49025 and B. coagulans ATCC7050 (approximately 107 CFU ml-1) in citric acid (0,02 M, pH 3.5 to 5.0) or tomato sauce (pH 4.2 or 5.0) were subjected to pressure treatments at 100 to 800 MPa (5 to 60°C, 10 min). After processing, spore inactivation and germination was determined by plating the suspensions either directly, or after an additional heat treatment to kill the germinated spores. All experiments were conducted in triplicate and data are expressed as mean values ± standard errors of mean. Results: In general, little or no inactivation of A. acidoterrestris spores after a HHP treatment (100 to 800 MPa, 10 min) was noticed at all temperatures tested. However, treatment at low pressures (< 400 MPa, optimum of about 200 MPa) caused germination of A. acidoterrestris spores. The proportion of germinated spores increased with increasing process temperature, upto 99%. Spores of B. coagulans also germinated upon high pressure treatment, but showed more germination as pressure increased. Significance: The data show that germination of A. acidoterrestris and B. coagulans spores can be induced by high hydrostatic pressure treatment in an acidic environment. In contrast, spores of non-acidophiles, like B. subtilis, cannot be pressure-germinated in acidic conditions. We anticipate that it will be possible to inactivate A. acidoterrestris and B. coagulans spores by applying a two-step process consisting of a mild high pressure treatment to induce germination, followed by a mild heat treatment or a more elevated pressure treatment to kill the germinated spores. T7-11 Membrane Damage and Microbial Inactivation by UV-light and Radio Frequency Electric Fields Processing of Apple Juice DIKE UKUKU and David Geveke ARS-USDA, FSIT-ERRC, Wyndmoor, PA, USA Introduction: Radio frequency electric fields (RFEF) and UV-light treatments have been reported to inactivate bacteria in liquid foods. However, information on the efficacy of bacterial inactivation by combined treatments of RFEF and UVlight technologies is limited. Purpose: In this study, we investigated the relationship between cell injury and inactivation of Escherichia coli K-12 in apple juice treated with a combination of RFEF and UV-light. Methods: Apple juice purchased from a wholesale distributor was inoculated with Escherichia coli K-12 at 7.8 log CFU/ ml, processed with a laboratory scale RFEF at 20 kHz, 15 kV/cm for 170 µs at a flow rate of 540 ml/min followed by UVlight treatment at 40C. Treated samples were analyzed for leakage of UV-absorbing substances as a function of membrane damage and were plated (0.1 ml) on Sorbitol MacConkey Agar (SMAC) and Trypticase Soy Agar (TSA) plates to determine viability loss and percent injury. Results: UV-light treatment alone caused 6.5 log reduction of E. coli in apple juice while RFEF caused only 1.5 log reduction. Percent injury caused by RFEF and UV-light processing alone averaged 95% and < 1%, respectively. A combination of the two processing treatments did not increase cell injury or leakage of UV-substances. Similarly, the number of viability loss determined was not significantly (P 0.05) different than UV-light treated samples. Significance: The results of this study suggest that RFEF treatment causes more injury to the bacterial cells leading to more cellular leakage of UV-substances than UV-light treatment. Also, that the effect of the two processing treatment combination was not synergetic. T7-12 Assessment and Modelling of the Microbial Spoilage of Four Traditional Greek Appetizers Stavros G. Manios, Stavros Ketsatis, Anastasia E. Kapetanakou, Antonia S. Gounadaki and PANAGIOTIS N. SKANDAMIS Agricultural University of Athens, Food Science & Technology, Kallithea, Greece Introduction: Traditional Greek appetizers are emulsified foods made of vegetables, bread, legume, cheese, and sometimes mayonnaise. Their shelf life ranges from 2 to 3 months under refrigeration and relies on acetic (vinegar) or citric (lemon) acid (pH 3.6-3.9) and NaCl (3-7%); however, in tropical climates, where temperatures during distribution and household refrigerators may often exceed 5 or even 10°C, remarkable microbial growth may occur, despite their intrinsic stability. Therefore, assessment/prediction of their shelf life via a relevant decision support tool, based on the timetemperature exposure of the products in the market, is of high value. Abstract Book — 53 Technical

IAFP 2009 Program Book and Abstract Book

Table of Contents for the Digital Edition of IAFP 2009 Program Book and Abstract Book