Catherine Bowe
Northumbria University
United Kingdom
Title: The impact of spore aggregation on viable and total counts of bacterial spores in model fruit juices
Biography
Biography: Catherine Bowe
Abstract
Contamination of ambient stable fruit juices is a common concern for all drinks manufacturers. It is imperative that an accurate bacterial enumeration method is in place to avoid over or under-estimating the remaining bacterial count in all products. Aggregation can be common in spore forming organisms such as Alicyclobacillus acidoterrestris (a food spoilage organism) and Bacillus cereus (a food poinsoning organism). In this communication, spores of B. subtilis, a good safe alternative to model pathogenic organisms, were exposed to different model fruit juices and their total counts as well as viable counts were assessed by plating and flow cytometry (FCM)
Aims
• To assess the perceived viable counts of spores across a range of different pH conditions and compare these with the total counts via FCM
• Compare these results with spore counts with a non-ionic surfactant present to gain an insight into ‘true’ counts
Spores were examined in simulated fruit juice at pH 0.5, 1 3 and 5, acidified with citric acid. Flow cytometry (FCM) was implemented to measure viability, physiology and total counts of spores. Viability was also analysed by plating. Particle size distribution (PSD) was also carried out on spores with and without Tween 20, and the size of aggregates compared
In the present research, the levels of aggregation were assessed by each method, using the Tween supplemented samples to show total counts, and the non- Tween samples to illustrate the percentage aggregation.
The impact of spore aggregation on bacterial contamination of drinks is an overlooked aspect, possibly due to limitations in methodological analyses. As such, tools which provide total counts, such as flow cytometry, are extremely valuable in this line of research.