Preliminary evaluation of flow cytometry for the detection of yeasts in soft drinks

The ChemFlow flow cytometry system was evaluated for the rapid detection of yeast in a range of soft drinks. The minimum numbers of Saccharomyces cerevisiae cells that could be reliably detected in different products directly after addition were as follows: lemonade, 50/ml; orange carbonate, 2500/ml; orange juice, 6300/ml and tomato juice, 14000/ml. These results were obtained using provisional protocols which are being developed to optimize the technique for this application. The ChemFlow system has potential for detecting significant numbers of spoilage yeasts directly in products and takes less than 1 h for sample preparation and analysis. The sensitivity of the technique, in conjunction with the correct forced incubation of samples, has the potential for assessing the total microbial load of drinks immediately after production.