Purpose: Traditional methods require a total of nine days for detection & enumeration. The goal was to reduce time to results while maintaining the qualitative and quantitative accuracy of microbial analysis.
Methods: A variety of rapid technologies have been evaluated and fluorescence technology selected as most suitable for detecting spoiler microorganisms in beer mixes with a low or 0% alcohol content. Validation has been performed according to ISO 16140 on 3 beers: soft drink mixes in a comparative study using a rapid method of membrane filtration and fluorescence staining and the reference method of Wallenstein agar incubated at 27°C for 9 days. Three microorganisms were tested (Zygosacharomyces bailii, Dekkera anomala, Dekkera bruxellensis). Six bottles of each product were spiked with the 3 microorganisms (10 CFU/filtered volume) and incubated for 3 days at 27°C on Wallenstein agar, followed by staining and read out for the rapid method and re-incubation for another 3 days to compare results with reference method after 6 days. For verification 15 replicates/ product were analyzed with both methods. As results might be absent or near 1 CFU/bottle, a number of positive controls were prepared.
Results: Validation results show a recovery rate above 70%, efficacy of 100% and a relative sensitivity and specificity of 100% stating that both methods are equivalent. Verification results show efficacy of 90%, relative sensitivity and specificity of 86% and 93%, a recovery/accuracy level of above 70% and a precision similar to the traditional method.
Significance: The validation study confirms that MilliporeSigma Milliflex Quantum can reduce the time to result to half or one third of the time required by the standard method. Faster results allow beverage manufactures to react faster and reduce risk of quality and safety issues.