Einfluss der Probenlagerung ueber Nacht auf die aerobe mesophile Keimzahl von vorgekochten pflanzlichen Lebensmitteln

摘要

The object of this study was to determine the effect of cold storage of recontam-inated cooked foods of plant origin on the total plate count when the analysis was performed only the day after the sample was taken. The possibility of storing samples in the laboratory for up to 20 h would permit samples taken in the evening to be examined on the following day. The results of seven laboratories have been evaluated. A number of 86 samples (cooked pasta, vegetables, rice, maize and sauces) were analyzed in duplicates first the day of sampling and second the next day after cold storage during 20 h in the laboratory refrigerator. The median growth factor observed was 2.4. The repeatability, estimated by robust statistics, determined the confidence interval by a ratio of 3.5. It comprised mainly the scatter due to the inho-mogeneity of the samples. However, after cold storage over night 42 % of the samples showed a growth factor of more than 3.5. Two additional test series with an extended number of similar samples lead to about the same statistical values. Therefore, the cold storage of cooked food samples until the following day seems not to be advisable. Increased plate numbers might be responsible for unjustified contestations. These observations are of considerable practical consequences for the monitoring of microbial quality of cooked ready-to-serve food and foodstuffs by the official food control authorities.