title: Effect of physical properties on the stability of Lactobacillus bulgaricus in a freeze-dried galacto-oligosaccharides matrix.
abstract: The ability of galacto-oligosaccharides (GOS) to protect Lactobacillus delbrueckii subsp. bulgaricus upon freeze drying was analyzed on the basis of their capacity to form glassy structures. Glass transition temperatures (T(g)) of a GOS matrix at various relative humidities (RH) were determined by DSC. Survival of L. bulgaricus in a glassy GOS matrix was investigated after freezing, freeze drying, equilibration at different RHs and storage at different temperatures. At 32 °C, a drastic viability loss was observed. At 20 °C, the survival was affected by the water content, having the samples stored at lower RHs, the highest survival percentages. At 4°C, no decay in the cells count was observed after 45 days of storage. The correlation between molecular mobility [as measured by Proton nuclear magnetic resonance (¹H NMR)] and loss of viability explained the efficiency of GOS as cryoprotectants. The preservation of microorganisms was improved at low molecular mobility and this condition was obtained at low water contents and low storage temperatures. These results are important in the developing of new functional foods containing pre and probiotics.
authors.affiliation: Centro de Investigación y Desarrollo en Criotecnología de Alimentos-CIDCA, Conicet La Plata, UNLP, 1900 La Plata, Argentina.
authors.forename: E Elizabeth
authors.initials: EE
authors.lastname: Tymczyszyn
authors.forename: Natalia
authors.initials: N
authors.lastname: Sosa
authors.forename: Esteban
authors.initials: E
authors.lastname: Gerbino
authors.forename: Ayelen
authors.initials: A
authors.lastname: Hugo
authors.forename: Andrea
authors.initials: A
authors.lastname: Gómez-Zavaglia
authors.forename: Carolina
authors.initials: C
authors.lastname: Schebor
mesh_terms: D002462:Cell Membrane / Q000502:physiology; D015169:Colony Count, Microbial; D003451:Cryoprotective Agents / Q000737:chemistry*; D005612:Freeze Drying / Q000379:methods*; D006813:Humidity; D007778:Lactobacillus / Q000502:physiology*; D050296:Microbial Viability; D009844:Oligosaccharides / Q000737:chemistry*; D019936:Probiotics; D044366:Transition Temperature; D014867:Water / Q000502:physiology
chemical_list: D003451:Cryoprotective Agents; D009844:Oligosaccharides; D014867:Water