Operating Conditions That Affect the Resistance of Lactic Acid Bacteria to Freezing and Frozen Storage

Fonseca, Fernanda; Béal, Catherine; Corrieu, Georges

doi:10.1006/cryo.2001.2343

Cited by 96 publications

(50 citation statements)

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“…Although freeze drying is the conventional drying technique used commercially by starter culture manufactures, it is lengthy and more expensive than other drying processes (Fonseca et al 2001, Ampatzoglou et al 2010, Morgan et al 2006). Many attempts have been made to develop alternative drying processes at lower cost and some authors have reported reasonable cell viability after drying (Tymczyszyn et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Different Methods of Probiotics Stabilization

Goderska¹

2012

Probiotics

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Section: Introductionmentioning

confidence: 99%

Different Methods of Probiotics Stabilization

Goderska¹

2012

Probiotics

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“…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).…”

mentioning

confidence: 99%

“…Glycerol was added to the supernatant obtained after centrifugation of the fermented medium, since it has been reported to be a good cryoprotectant of LAB (9,17,33). The final concentration of glycerol in the supernatant was 10% (wt/wt).…”

mentioning

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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“…The process of freezing appeared to have different effects on different LAB as well as different effects on strains within the same genus. Moreover, the freezing response of the strains depends on the time of the cold shock process and the induction of cryotolerance appears to be dependent on the growth phase in which the cold shock took place [43][44][45][46][47].…”

Section: Principal Responses To the Most Common Stressesmentioning

confidence: 99%