Effect of Protective Agents on the Viability of Geotrichum candidum during Freeze‐Drying and Storage

Abstract

The effect of 3 cryoprotective agents (trehalose, sucrose, and maltose) on the survival of concentrated cultures of Geotrichum candidum was studied. Initially, the effect of the carbohydrates at 9% and 23% concentrations or combined with skim milk (16%) was compared to the control (skim milk alone) immediately after freeze-drying. Two freeze-drying shelf temperatures, 25 degrees C and 35 degrees C, were investigated. Afterwards, the survival of G. candidum freeze-dried with carbohydrates at 23% concentration (alone or combined with skim milk 16%) was studied during 12 wk of storage at 4 degrees C, in the darkness, under vacuum, and at 0% relative humidity. The glass transition temperature (T(g)) of the dehydrated protective agents was measured by differential scanning calorimetry. The results showed that the survival after freeze-drying was proportional to the concentration of the protective agents, with skim milk alone giving poor survival of G. candidum. However, when skim milk was combined with disaccharides, a clear improvement was noted. No general tendency of shelf temperature on the survival of G. candidum was noted immediately after freeze-drying. However, changes in the viability were observed during storage. Glass transition temperature (T(g)) of protective agents linked to their moisture may contribute to predict the stability of lyophilized G. candidum during freeze-drying and storage.

Effect of drying methods of microencapsulated Lactobacillus acidophilus and Lactococcus lactis ssp. cremoris on secondary protein structure and glass transition temperature as studied by Fourier transform infrared and differential scanning calorimetry

“…The combination of mannitol with sodium caseinate appeared useful to increase T g of the mixture due to the high T g of sodium caseinate. A similar study showed that incorporation of skim milk into disaccharides increased T g of freeze-dried Geotrichum candidum (Hamoudi et al, 2007). In our study, no T g of pure crystalline mannitol (at 10°C) was detected, indicating that mannitol strongly interacted with other substances (Kalichevsky and Blanshard, 1992;Taylor and Zografi, 1998).…”

Microencapsulation of Lactobacillus paracasei by spray freeze drying

“…However, when this method was employed for drying probiotic bacteria and other cells, undesirable effects such leakage of the cell membrane due to changes in the physical state of membrane lipids or changes in the structure of sensitive proteins in the bacteria cell occur (Leslie, Israeli, Lighthart, Crowe, & Crowe, 1995;Teixeira, Castro, & Kirby, 1996;Teixeira, Castro, Malcata, & Kirby, 1995). Protective solutes such as cryoprotectants (saccharides and polyols) and other compatible solutes like adonitol, betaine, glycerol and skim milk were used to increase bacteria's viability and increase their survival during freeze-drying and subsequent storage (de Valdez, Degiori, Holgado, & Oliver, 1983;Hamoudi, Goulet, & Ratti, 2007;Selmer-Olsen, Birkeland, & Sorhaug, 1999). These studies lead to the conclusion that the effect of each protective agent on the viability of a specific LAB strain during or following the freeze-drying process have to be determined on a case-bycase basis (Carvalho et al, 2004).…”

Survival of Freeze-dried Leuconostoc mesenteroides and Lactobacillus plantarum Related to Their Cellular Fatty Acids Composition during Storage

“…A number of factors, such as temperature, atmosphere, exposure to light and moisture influence the viability of freeze-dried cultures [16]. It is well established that cryoprotectants are almost indispensable when freezing and drying microorganisms, but the contribution of these compounds to stability of dried microorganisms during storage is discussed [17]. The disadvantages of dried cultures undermine their application, but advantages can outweigh disadvantages if the inactivation during storage can be more clearly understood and consequently reduced.…”