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The Impact of Annealing Methods on the Encapsulating Structure and Storage-Stability of Freeze-Dried Pellets of Probiotic Bacteria

Palmkron, Shuai Bai ; Bergenståhl, Björn LU orcid ; Hall, Stephen LU ; Håkansson, Sebastian LU ; Wahlgren, Marie LU orcid ; Larsson, Emanuel LU and Fureby, Anna Millqvist LU (2024) In Pharmaceutical Research 41. p.1671-1682
Abstract

Objective: This paper investigates the critical role of material thickness in freeze-dried pellets for enhancing the storage stability of encapsulated bacteria. Freeze dried material of varying thicknesses obtained from different annealing durations is quantified using Scanning Electron Microscopy (SEM) and X-ray microtomography (μCT), the material thickness is then correlated to the storage stability of the encapsulated cells. Methods: A formulation comprising of sucrose, maltodextrin, and probiotic cells is quenched in liquid nitrogen to form pellets. The pellets undergo different durations of annealing before undergoing freeze-drying. The material thickness is quantified using SEM and μCT. Storage stability in... (More)

Objective: This paper investigates the critical role of material thickness in freeze-dried pellets for enhancing the storage stability of encapsulated bacteria. Freeze dried material of varying thicknesses obtained from different annealing durations is quantified using Scanning Electron Microscopy (SEM) and X-ray microtomography (μCT), the material thickness is then correlated to the storage stability of the encapsulated cells. Methods: A formulation comprising of sucrose, maltodextrin, and probiotic cells is quenched in liquid nitrogen to form pellets. The pellets undergo different durations of annealing before undergoing freeze-drying. The material thickness is quantified using SEM and μCT. Storage stability in both oxygen-rich and oxygen-poor environments is evaluated by measuring CFU counts and correlated with the pellet structure. Results: The varying annealing protocols produce a range of material thicknesses, with more extensive annealing resulting in thicker materials. Storage stability exhibits a positive correlation with material thickness, indicating improved stability with thicker materials. Non-annealed pellets exhibit structural irregularities and inconsistent storage stability, highlighting the impracticality of avoiding annealing in the freeze-drying process. Conclusions: Extensive annealing not only enhances the storage stability of probiotic products but also provides greater control over the freeze-drying process, ensuring homogeneous and reproducible products. This study underscores the importance of material thickness in freeze-dried pellets for optimizing storage stability for probiotic formulations, and emphasize the necessity of annealing as a critical step in freeze-drying quenched pellets to achieve desired structural and stability outcomes.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
annealing, collapse, encapsulated bacteria, freeze-drying, oxygen barrier, pellets, relaxation, shelf-life, structural analysis, tomography
in
Pharmaceutical Research
volume
41
pages
12 pages
publisher
Springer
external identifiers
  • pmid:39078576
  • scopus:85200033293
ISSN
0724-8741
DOI
10.1007/s11095-024-03751-w
language
English
LU publication?
yes
additional info
Publisher Copyright: © The Author(s) 2024.
id
d8a4709b-e583-42cc-9bd8-485d873ae70b
date added to LUP
2024-09-02 22:48:09
date last changed
2025-07-09 17:25:32
@article{d8a4709b-e583-42cc-9bd8-485d873ae70b,
  abstract     = {{<p>Objective: This paper investigates the critical role of material thickness in freeze-dried pellets for enhancing the storage stability of encapsulated bacteria. Freeze dried material of varying thicknesses obtained from different annealing durations is quantified using Scanning Electron Microscopy (SEM) and X-ray microtomography (<sub>μ</sub>CT), the material thickness is then correlated to the storage stability of the encapsulated cells. Methods: A formulation comprising of sucrose, maltodextrin, and probiotic cells is quenched in liquid nitrogen to form pellets. The pellets undergo different durations of annealing before undergoing freeze-drying. The material thickness is quantified using SEM and <sub>μ</sub>CT. Storage stability in both oxygen-rich and oxygen-poor environments is evaluated by measuring CFU counts and correlated with the pellet structure. Results: The varying annealing protocols produce a range of material thicknesses, with more extensive annealing resulting in thicker materials. Storage stability exhibits a positive correlation with material thickness, indicating improved stability with thicker materials. Non-annealed pellets exhibit structural irregularities and inconsistent storage stability, highlighting the impracticality of avoiding annealing in the freeze-drying process. Conclusions: Extensive annealing not only enhances the storage stability of probiotic products but also provides greater control over the freeze-drying process, ensuring homogeneous and reproducible products. This study underscores the importance of material thickness in freeze-dried pellets for optimizing storage stability for probiotic formulations, and emphasize the necessity of annealing as a critical step in freeze-drying quenched pellets to achieve desired structural and stability outcomes.</p>}},
  author       = {{Palmkron, Shuai Bai and Bergenståhl, Björn and Hall, Stephen and Håkansson, Sebastian and Wahlgren, Marie and Larsson, Emanuel and Fureby, Anna Millqvist}},
  issn         = {{0724-8741}},
  keywords     = {{annealing; collapse; encapsulated bacteria; freeze-drying; oxygen barrier; pellets; relaxation; shelf-life; structural analysis; tomography}},
  language     = {{eng}},
  pages        = {{1671--1682}},
  publisher    = {{Springer}},
  series       = {{Pharmaceutical Research}},
  title        = {{The Impact of Annealing Methods on the Encapsulating Structure and Storage-Stability of Freeze-Dried Pellets of Probiotic Bacteria}},
  url          = {{http://dx.doi.org/10.1007/s11095-024-03751-w}},
  doi          = {{10.1007/s11095-024-03751-w}},
  volume       = {{41}},
  year         = {{2024}},
}