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Author Spotlight: Process Development for the Spray-Drying of Probiotic Bacteria and Evaluation of the Product Quality
Published on: April 7, 2023
Dynamics of Active Fluorescent Units (AFU) and Water Activity (aw) Changes in Probiotic Products-Pilot Study
Katarzyna Sielatycka1,2, Joanna Śliwa-Dominiak2, Martyna Radaczyńska2
1Institute of Biology, Faculty of Exact and Natural Sciences, University of Szczecin, ul. Felczaka 3c, 71-415 Szczecin, Poland.
Abstract:
The flow cytometry method (FCM) is a widely renowned practice increasingly used to assess the microbial viability of probiotic products. Additionally, the measurement of water activity (aw) can be used to confirm the presence of viable cells in probiotic products throughout their shelf lives. The aim of this study was to investigate the correlation between changes in aw and variations in active fluorescent units (AFU), a unit commonly used in flow cytometry method, during the aging of probiotic products containing freeze-dried bacteria. We controlled the stability of probiotic products for bacterial counts (using ISO 19344 method) and aw levels in commercially available capsules containing freeze-dried bacteria such as Lactobacillus sp. or combinations of Lactobacillus sp. and Bifidobacterium sp. in standard conditions (25 ± 2 °C and 60% relative humidity) over a period of 24 months. During this time, the bacterial contents decreased by 0.12 Log10 in the single-strain product, by 0.16 Log10 in the two-strain product and by 0.26 Log10 in the multi-strain product. With the increase in aw, the number of bacteria decreased but the aw at the end point of the stability study did not exceed 0.15 in each of the three tested products. FCM combined with aw is a prospective analysis that can be used to assess the stability of probiotic products, both for its ability to detect bacterial viability and for practical (analysis time) and economic reasons.
Insights
Flow cytometry method (FCM) and water activity (aw) can assess probiotic stability. This study correlated aw changes with active fluorescent units (AFU) in aging probiotic capsules, showing a viable method for stability testing.
Area of Science:
- Microbiology
- Food Science
- Analytical Chemistry
Background:
- Flow cytometry method (FCM) is crucial for assessing microbial viability in probiotics.
- Water activity (aw) measurement aids in confirming viable cell presence throughout probiotic shelf life.
Purpose of the Study:
- To investigate the correlation between water activity (aw) and active fluorescent units (AFU) during the aging of freeze-dried probiotic products.
- To evaluate the stability of commercial probiotic capsules containing Lactobacillus and Bifidobacterium species.
Main Methods:
- Controlled stability testing of probiotic capsules under standard conditions (25°C, 60% RH) for 24 months.
- Measured bacterial counts using ISO 19344 and water activity (aw) levels.
- Assessed microbial viability using flow cytometry method (FCM) and quantified results in active fluorescent units (AFU).
Main Results:
- Bacterial content decreased over 24 months, with reductions of 0.12 Log10 (single-strain), 0.16 Log10 (two-strain), and 0.26 Log10 (multi-strain).
- Increased aw correlated with decreased bacterial counts, but aw remained below 0.15 throughout the study.
- Active fluorescent units (AFU) measured by FCM showed a correlation with bacterial count changes.
Conclusions:
- Flow cytometry method (FCM) combined with water activity (aw) analysis is a promising approach for assessing probiotic product stability.
- This combined method offers advantages in detecting bacterial viability, analysis time, and cost-effectiveness.
- The study demonstrates the utility of FCM and aw for quality control and shelf-life determination of probiotic supplements.
