Viability and thermal stability of a strain of Saccharomyces cerevisiae freeze-dried in different sugar and polymer matrices |
| |
Authors: | P Lodato M Segovia de Huergo M P Buera |
| |
Institution: | (1) Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, (1428) Buenos Aires, Argentina, AR;(2) Departamento de Ingeniería Química, Facultad de Ingeniería, Universidad de Buenos Aires, Argentina, AR |
| |
Abstract: | The viability and thermal stability of a freeze-dried yeast strain were studied in relation to some physical properties of
the matrices in which the cells were freeze-dried. Samples of inoculum with solutions of the matrix components polyvinylpyrrolidone
(PVP), maltose, trehalose, maltodextrins, or mixtures of maltodextrin and trehalose] and controls without matrices were freeze-dried
and then equilibrated at several relative humidities. Viability was determined before and after freeze-drying and after heat
treatment (100 min at 70 °C). Freeze-drying with trehalose, PVP, maltose or 1.8-kDa maltodextrin, and mixtures of maltodextrin/trehalose
increased viability in comparison with controls. The 3.6-kDa maltodextrin was ineffective at protecting the cells during freeze-drying.
The glass transition temperature (T
g), which depends on moisture content, was indicated as a possible factor to determine the stability of labile materials. Protective
effects of the excipients during thermal treatment were analysed in relation to the physical changes (collapse or structural
shrinkage) which were dependent on the T
g of the systems. The presence of a certain amount of amorphous disaccharides during freeze-drying and heating was found to
be a critical factor for ensuring cell viability, which was protected even in rubbery (above T
g) matrices.
Received: 4 December 1998 / Received last revision: 2 March 1999 / Accepted: 14 March 1999 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|