Death of Freeze-Dried Lactobacillus bulgaricus during Rehydration

Abstract

The viability of freeze-dried Lactobacillus bulgaricus B-1 was affected by rehydration temperature, and maximum recovery of the viable cells was obtained when they were rehydrated at 20 to 25°C. Cellular ribonucleotides leaked out from the freeze-dried cells during rehydration, but there was no correlation between the viability of cells and the amount of leaked substances. Rehydration of the freeze-dried cells in the presence of RNase caused marked loss of viability. These results suggest that the cell surface was damaged by freeze-drying and its selective permeability was lost to some extent.

Effect of time of inoculation, starter addition, oxygen level and salting on the viability of probiotic cultures during Cheddar cheese production

“…It was not investigated if this was linked to the direct inoculation of freeze-dried cells rather than a fresh liquid culture. It has been shown that cfu counts following rehydration are highly influenced with the osmolarity of the reconstitution fluid (Choate & Alexander, 1967), the rehydration temperature (Morichi, Irie, Yano, & Kembo, 1967) as well as by the rate and volume of medium used for rehydration (De Valdez, De Giori, De Ruiz Holgado, & Olivier, 1985). Although viability losses upon inoculation occurred, the use of lyophilised cells was maintained for our assays because it is the usual procedure used in industry.…”

Spray drying as a method for preparing concentrated cultures of Lactobacillus bulgaricus

“…Membrane damage: has been reported as a site of damage common to different type of stresses: freeze drying (Morichi et al 1967), freeze and vacuum drying (Brennan et al 1986) and heat treatments (Hurst and Hughes 1975;Hoover and Gray 1977). 0 Growth phase: it is well known that cells at exponential phase of growth are more sensitive to treatments such as heating (Griffiths and Haigh 1973;Hurst et al 1974;Teixeira et al 1994).…”

“…0 Heat shock: it has been reported that heat shock can increase the resistance of different bacteria to heat treatments (Hogg 1989;Whitaker and Batt 1991;Teixeira et al 1994). 0 Rehydration: the rehydration of dried bacterial cells is a critical process which sometimes affects the cell viability (Morichi et al 1967); however, the rehydration methods actually used by earlier workers have not always been described. The reasons for using determined conditions by some workers have, in general, not been supported by comparisons with alternative procedures.…”