Survival kinetics of lactic acid starter cultures during and after freeze drying

Bozoğlu, T. Faruk; Özilgen, Mustafa; Bakır, Ufuk

doi:10.1016/0141-0229(87)90082-2

Cited by 101 publications

(51 citation statements)

References 9 publications

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“…The surviving fraction of freeze-dried LAB (L. delbrueckii subsp. bulgaricus and Streptococcus thermophilus) also increased with increasing biomass concentrations (it was highest at 10 10 cells ml Ϫ1 ; the concentrations studied were 10 4 to 10 10 cells ml Ϫ1 ), which was ascribed to mutual shielding of the microorganisms against severe environmental conditions by reducing the interfacial area between cells and the external medium (4).…”

Section: Discussionmentioning

confidence: 99%

Stabilization of Frozen Lactobacillus delbrueckii subsp. bulgaricus in Glycerol Suspensions: Freezing Kinetics and Storage Temperature Effects

Fonseca

Marin

Morris

2006

Appl Environ Microbiol

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The interactions between freezing kinetics and subsequent storage temperatures and their effects on the biological activity of lactic acid bacteria have not been examined in studies to date. This paper investigates the effects of three freezing protocols and two storage temperatures on the viability and acidification activity of Lactobacillus delbrueckii subsp. bulgaricus CFL1 in the presence of glycerol. Samples were examined at ؊196°C and ؊20°C by freeze fracture and freeze substitution electron microscopy. Differential scanning calorimetry was used to measure proportions of ice and glass transition temperatures for each freezing condition tested. Following storage at low temperatures (؊196°C and ؊80°C), the viability and acidification activity of L. delbrueckii subsp. bulgaricus decreased after freezing and were strongly dependent on freezing kinetics. High cooling rates obtained by direct immersion in liquid nitrogen resulted in the minimum loss of acidification activity and viability. The amount of ice formed in the freeze-concentrated matrix was determined by the freezing protocol, but no intracellular ice was observed in cells suspended in glycerol at any cooling rate. For samples stored at ؊20°C, the maximum loss of viability and acidification activity was observed with rapidly cooled cells. By scanning electron microscopy, these cells were not observed to contain intracellular ice, and they were observed to be plasmolyzed. It is suggested that the cell damage which occurs in rapidly cooled cells during storage at high subzero temperatures is caused by an osmotic imbalance during warming, not the formation of intracellular ice.Concentrates of lactic acid bacteria (LAB) are widely used as starters for manufacturing cheese, fermented milk, meat, vegetables, and bread products (19). Freezing and storage at low temperatures (ϽϪ40°C) are commonly applied to preserve the viability of concentrates while maintaining their technological properties upon thawing (acidification activity, production of aroma compounds, and contribution to product texture). However, bacterial resistance to freezing and to frozen storage depends on the strain, culture conditions before freezing, harvesting, formulation (type and concentration of cryoprotectant), freezing conditions, and final storage temperature (9).Freezing is a critical step in the production of LAB concentrates, as it affects both the viability and acidification activity upon thawing (10, 32). However, the mechanisms of freezing damage to bacteria are not well understood. Two damage mechanisms dependent on the cooling rate have usually been proposed. At low freezing rates, cellular damage is principally caused by osmotic stress to cells (so-called "solution effects") (24). The formation of extracellular ice induces high solute concentrations in the extracellular medium, exposing the cells to an increase in ionic concentration, changes in pH, etc., for extended periods of time. At very high cooling rates, it has been assumed that damage is due to the formation of int...

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Section: Discussionmentioning

confidence: 99%

Stabilization of Frozen Lactobacillus delbrueckii subsp. bulgaricus in Glycerol Suspensions: Freezing Kinetics and Storage Temperature Effects

Fonseca

Marin

Morris

2006

Appl Environ Microbiol

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“…Possible reasons for such a realisation are somewhat puzzling; it was suggested [20] that gene transfer between strains may lead to differences in phenotype between various Lactococcus lactis strains. Previous work claimed an effect of bacterial cell size on survival during freezing and freeze-drying [2,7]; according to Fonseca et al [7], the higher the surface area of the cell, the higher the membrane damage due to extracellular ice crystal formation during freezing. This could provide a possible explanation for the results presented, since it was observed that the survival of the various species was related to their size: enterococci (small spherical cells) were more resistant during storage in the dried state than lactobacilli (larger rods).…”

Section: Discussionmentioning

confidence: 99%

Protective effect of sorbitol and monosodium glutamate during storage of freeze-dried lactic acid bacteria

Carvalho

Silva

et al. 2003

Lait

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-The effects of sorbitol and monosodium glutamate upon survival during storage of freeze-dried Lactobacillus bulgaricus, Lactobacillus plantarum, Lactobacillus rhamnosus, Enterococcus durans and Enterococcus faecalis were examined. There were no significant differences in survival during freeze-drying after addition of sorbitol or monosodium glutamate. However, these compounds were found to increase the stability of most strains during long-term storage. Various survival patterns were observed among the strains considered. However, for most of them, both compounds were proven effective in maintaining high degrees of viability over long periods of storage.Starter culture / preservation / additive / processing / viability Résumé -Effet protecteur du sorbitol et du glutamate monosodique pendant le stockage de bactéries lactiques lyophilisées. Les effets du sorbitol et du glutamate monosodique sur la survie des souches lyophilisées de Lactobacillus bulgaricus, Lactobacillus plantarum, Lactobacillus rhamnosus, Enterococcus durans et Enterococcus faecalis pendant le stockage ont été étudiés. On n'a pas trouvé de différences significatives pendant la lyophilisation, après l'addition de sorbitol ou de glutamate monosodique. Cependant, l'addition de ces composés a augmenté la stabilité de la plupart des souches pendant le stockage prolongé. Différents profils de survie ont été observés parmi les souches considérées ; toutefois, pour la plupart des souches les deux composés étaient efficaces dans le maintien de degrés élevés de viabilité pendant de longues périodes de stockage. Levain / conservation / additif / traitement / viabilité

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“…Different survival rates in films during freeze drying might be due to the different initial lactobacilli concentration in films. In general, surviving fraction of the microorganisms increases with the increasing biomass concentration before freeze-drying, and this is attributed to the mutual shielding effect of the microorganisms against the severe conditions of the external medium (20). Furthermore, cellular damage induced by the hypertonic calcium solutions could have accumulated through the freezing and drying processes (21).…”

Section: Discussionmentioning

confidence: 99%

Alginate Films Containing Viable Lactobacillus Plantarum: Preparation and In Vitro Evaluation

2012

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Abstract. The objective of the study was to develop calcium alginate films, containing Lactobacillus plantarum ATCC 8040 with preserved and stable viability and antibacterial activity. L. plantarum-loaded films containing different calcium concentrations were physically characterized for mechanical and bioadhesive properties and lactobacilli release. The viability and antibacterial activity of L. plantarum was studied before and after processing, and during 6 months of storage. A multiresistant clinical isolate, VIM-2-metalo-β-lactamase producing Pseudomonas aeruginosa, was used as an indicator strain. Interference between L. plantarum and films enhanced films elasticity, water absorption ability, release of lactobacilli, and decreased films adherence. A decrease of L. plantarum viability in alginate films (≤1 log unit) was observed after freeze drying. L. plantarum, at cell concentrations of 10 8 cfu/ml, was inhibitory active. The viability and antibacterial activity of the immobilized lactobacilli remained stable during 6 months of storage. The study has proved the potential of alginate films to deliver L. plantarum in high numbers to individuals.

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Survival kinetics of lactic acid starter cultures during and after freeze drying

Cited by 101 publications

References 9 publications

Stabilization of Frozen Lactobacillus delbrueckii subsp. bulgaricus in Glycerol Suspensions: Freezing Kinetics and Storage Temperature Effects

Stabilization of Frozen Lactobacillus delbrueckii subsp. bulgaricus in Glycerol Suspensions: Freezing Kinetics and Storage Temperature Effects

Protective effect of sorbitol and monosodium glutamate during storage of freeze-dried lactic acid bacteria

Alginate Films Containing Viable Lactobacillus Plantarum: Preparation and In Vitro Evaluation

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