Fachbereich Veterinärmedizin



    Bestimmung der mikrobiellen Belastung von rohem und hitzebehandeltem Fleisch mit dem Limulus-Test (2000)

    Dildei, Cornelia (WE 8)
    Niehoff, 2000 — 139 Seiten
    ISBN: 3-8311-1156-1
    Institut für Lebensmittelsicherheit und -hygiene

    Königsweg 69
    14163 Berlin
    +49 30 838 62550

    Abstract / Zusammenfassung

    In a model test 288 samples of minced beef were examined in 18 trials. The following tests were carried out both on fresh samples, as well as samples heated to 60, 80 and 1O0°C, and under different storage conditions (open or vacuum-packed at CC or 22"C over a period of up to 10 days): A sensory appraisal, the measurement of the LPScontent using the Limulus test and the determination of the total number of bacteria, the gramnegative bacteria, the Enterobacteriaceae and the Pseudomonas. Following these tests the samples were heat sterilised and the LPS-content was redetermined.The LPS-content, the sensory observations and the microbiological results are all dependent on the storage conditions. The LPS-content of open samples maintained at 22"C showed an increase by almost 5 orders in the course of 3 days (7.93 ± 0.93 log Eu/g), whereas vacuumpacked samples stored at 4"C showed an LPScontent of only 3.58 ± 0.90 log EU/g even after 10 days. At the same time the gramnegative value of the samples of minced beef maintained at room temperature increased by 2 orders. Values higher than 8 log EU/g where always accompanied by visible changes in the samples.The temperature pertaining in the time before conserving the meat determines the LPScontent. As an example, conserves made from meat stored at 22"C for 3 days show a LPS concentration approximately 3.5 times higher than fresh meat (absolute values between 3.15 and 8. 15 log EU/g). The results of the Limulus tests before and after the conservation process correlates highly with the results of the bacterial determination.In addition, 200 long-term beef conserves from different manufacturers after many years of storage and unknown pre-conservation parameters were subjected to sensory and Limulus tests. The maximum LPS value for all the conserves was 2.146 log EU/g (= 14 ng/g LPS) and is thus comparable with values determined for fresh meat in the model test. Several samples of conserved meat showed visible alteration but this was not accompanied by increases LPS levels. The visible alterations do ot seem to be causedby a decay of the raw meat such as caused by the known aerobal gramnegative surface flora of the meat.The model tests show that the Limulus test is a suitable screening device for conserved meats. A Limulus titration of more than 4.94 log EU/g is an indicator of hygienically doubtful material, as is a lower LPS content combined with visible alterations in the sample. In 90.8% of all cases the combination of a Limulus test and a sensory appraisal leads to he correct result with respect to the hygienic evaluation of the raw material.