Routine microbiological sampling and analysis of ground meat for quality control purposes - practical experience and statistical conclusions

The microbiological status of ground beef was routinely assessed at two pro duction facilities over a period of at least one year. Five re-plicate samp les were tested per day in accordance with European meat hygiene directives . In light of the high workload it was of great interest to decide whether the sample number could be reduced by combining the 5 single samples per lo t to a pool sample without causing a significance loss of information. Conc erning the "aerobic total plate count" as the main criterion the findings s howed that: Analysing a pool sample and using 3m reads in 129 of 131 lots of producer A to the same decision (acceptance/rejection) as 5 random samples in connect ion with the official 3-class-sampling plan (3(m)/c(m) = 2; M/c(M) = 0). In the case of producer B there have been 3 opposite decisions in 319 lots de spite of a very heterogeneous structure of the microbiological counts. More defective lots were observed on Mondays. No other trends could be observed . Obviously the microbiological results of 5 samples/day are only used for do cumentation and not for corrective actions or improvement of the hygienic s tatus, ii there are no severe objections against the bacteriological qualit y. Because the relatively poor information does not justify the analytical workload a modification of the official sampling plan is proposed: Following the principles of moving sum procedure the 5 random samples of mi nced meat per lot are combined to a pool sample and tested against the limi t 3m as long as no more than 2 plate counts exceed the limit 3m in the last 11 days of production.