Effect of physical properties on the stability of Lactobacillus bulgaricus in a freeze-dried galacto-oligosaccharides matrix

ELIZABETH TYMCZYSZYN; NATALIA SOSA; ESTEBAN GERBINO; AYELÉN HUGO; ANDREA GÓMEZ-ZAVAGLIA; CAROLINA SCHEBOR

INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY

ELSEVIER SCIENCE BV

Lugar: --; Año: 2012 vol. 155 p. 217 - 221

0168-1605

The ability of 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 (Tg) of GOS matrix were determined by DSC. Survival of L. bulgaricus in a glassy state GOS matrix was investigated after freezing, freeze-drying, equilibration at different relative humidities (11, 22 and 33%) and storage at different temperatures (4, 20 and 32 ºC). At 32 ºC, a drastic loss of viability was observed in all conditions assayed; at 20 ºC, the survival was affected by the water content, being the samples stored at lower RH, those depicting the highest survival percentages. At 4ºC, no decay in the cells count was observed after 45 days of storage. The incorporation of propidium iodide into the freeze-dried microorganisms indicated that the presence of GOS matrix is not sufficient to prevent membrane damage The correlation between molecular mobility (as measured by 1H NMR) and loss of viability explained the efficiency of GOS to preserve L. bulgaricus. The preservation of microorganisms is improved at low molecular mobilities and this condition could be obtained at low water content and at low storage temperatures. This integrated study about the thermophysical properties of GOS and their relation with the cell-sugar matrix provides information that could be important for the development of new functional foods containing pre and probiotics.