Impact of water activity, temperature, and physical state on the storage stability of Lactobacillus paracasei ssp. paracasei freeze-dried in a lactose matrix

Bettina Higl, Lone Kurtmann, Charlotte U. Carlsen, Jennifer Ratjen, Petra Först, Leif H. Skibsted, Ulrich Kulozik, Jens Risbo

Research output: Contribution to journalArticlepeer-review

127 Citations (Scopus)

Abstract

The aim of this study was to determine whether the combined effect of water activity and temperature on inactivation rates of freeze-dried microorganisms in a lactose matrix could be explained in terms of the glass transition theory. The stabilized glass transition temperature, Tg, of the freeze-dried products was determined by differential scanning calorimetry at two different temperatures, T (20 and 37°C), and different water activities (0.07-0.48). This information served as a basis for defining conditions of T and water activity, which led to storage of the bacteria in the glassy (J < T g) and nonglassy (T > Tg) states. The rates of inactivation of the dry microorganisms subjected to different storage conditions were determined by plate counts and could be described by first-order kinetics. Rates were analyzed as a function of water activity, storage temperature, and the difference between Tg and T. Inactivation below Tg was low; however, Tg could not be regarded as an absolute threshold of bacteria stability during storage. When the cells were stored in the nonglassy state (T > Tg), inactivation proceeded faster, however, not as rapid as suggested by the temperature dependence of the viscosity above the glass transition temperature. Furthermore, the first-order rate constant, k, was dependent on the storage temperature per se rather than on the temperature difference between the glass transition temperature and the storage temperature (T - Tg).

Original languageEnglish
Pages (from-to)794-800
Number of pages7
JournalBiotechnology Progress
Volume23
Issue number4
DOIs
Publication statusPublished - Jul 2007

Keywords

  • Bacteria/metabolism
  • Biotechnology/instrumentation
  • Cold Temperature
  • Freeze Drying
  • Glass
  • Kinetics
  • Lactobacillus/metabolism
  • Lactose/chemistry
  • Specimen Handling
  • Temperature
  • Water/chemistry
  • X-Ray Diffraction

Fingerprint

Dive into the research topics of 'Impact of water activity, temperature, and physical state on the storage stability of Lactobacillus paracasei ssp. paracasei freeze-dried in a lactose matrix'. Together they form a unique fingerprint.

Cite this