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Freeze-drying of Lactobacillus coryniformis Si3: effects of sucrose concentration, cell density, and freezing rate on cell survival and thermophysical properties
Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Center of Human Studies of Foodstuffs, Uppsala University, Uppsala, Sweden.
Department of Pharmacy, Uppsala University, Uppsala, Sweden.
Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
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2006 (English)In: Cryobiology, ISSN 0011-2240, E-ISSN 1090-2392, Vol. 53, no 1, 119-127 p.Article in journal (Refereed) Published
Abstract [en]

Freeze-drying is commonly used to stabilize lactic acid bacteria. Many factors have been reported to influence freeze-drying survival, including bacterial species, cell density, lyoprotectant, freezing rate, and other process parameters. Lactobacillus coryniformis Si3 has broad antifungal activity and a potential use as a food and feed biopreservative. This strain is considered more stress sensitive, with a low freeze-drying survival, compared to other commercialized antifungal lactic acid bacterial strains. We used a response surface methodology to evaluate the effects of varying sucrose concentration, cell density and freezing rate on Lb. coryniformis Si3 freeze-drying survival. The water activity of the dry product, as well as selected thermophysical properties of importance for freeze-drying; degree of water crystallization and the glass transition temperature of the maximally freeze concentrated amorphous phase (Tg') were determined. The survival of Lb. coryniformis Si3 varied from less than 6% to over 70% between the different conditions. All the factors studied influenced freeze-drying survival and the most important factor for survival is the freezing rate, with an optimum at 2.8 degrees C/min. We found a co-dependency between freezing rate and formulation ingredients, indicating a complex system and the need to use statistical tools to detect important interactions. The degree of water crystallization decreased and the final water activity increased as a function of sucrose concentration. The degree of water crystallization and Tg' was not affected by the addition of 10(8)-10(10) CFU/mI. At 10(11) CFU/ml, these thermophysical values decreased possibly due to increased amounts of cell-associated unfrozen water.

Place, publisher, year, edition, pages
Maryland Heights, USA: Elsevier, 2006. Vol. 53, no 1, 119-127 p.
Keyword [en]
Lactic acid bacteria, Lactobacillus coryniformis, freezing, degree of water crystallization, Tg, water activity, optimization, product quality
National Category
Food Engineering
Identifiers
URN: urn:nbn:se:oru:diva-52380DOI: 10.1016/j.cryobiol.2006.04.003ISI: 000239479200012PubMedID: 16756971ScopusID: 2-s2.0-33745809453OAI: oai:DiVA.org:oru-52380DiVA: diva2:972105
Available from: 2016-09-20 Created: 2016-09-19 Last updated: 2016-09-20Bibliographically approved

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Citation style
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