1H NMR investigation on the role of sorbitol for the survival of Lactobacillus paracasei ssp. paracasei in vacuum-dried preparations.
OBJECTIVE
The aim of this work was to study the effect of sorbitol as protective agent on the survival of the probiotic strain Lactobacillus paracasei ssp. paracasei (F19) after vacuum drying.


RESULTS
The survival was studied after different drying times and for various concentrations of sorbitol by plate count method. Furthermore, time domain 1H NMR studies on dehydrated suspensions of Lact. paracasei ssp. paracasei were performed to study the proton mobility in the dried samples. From the obtained signal, T2 relaxation times of single components and fractions with different proton mobility were determined. It was found out that the survival is increased by the presence of a minimum amount of sorbitol that is dependent on drying time. Furthermore, it is shown that the protective effect can only be observed below a critical water content of c. 20%. Nuclear magnetic resonance (NMR) results indicate a transition of sorbitol from liquid to solid like behaviour during drying. The onset of the transition coincides with the critical water content found for a protective effect.


CONCLUSIONS
The data suggest that sorbitol protons are incorporated into the dried cells of Lact. paracasei ssp. paracasei (F19) below the critical water content and therefore leading to an enhanced survival.


CONCLUSIONS
The results help to better understand the underlying mechanism of protection of Lact. paracasei ssp. paracasei using sorbitol and to establish vacuum drying as potential alternative drying technique to standard freeze drying.
Foerst
P
P
Food Process Engineering and Dairy Technology, Technische Universität München Weihenstephaner Berg 1, Freising, Germany.
Reitmaier
J
J
Food Process Engineering and Dairy Technology, Technische Universität München Weihenstephaner Berg 1, Freising, Germany.
Kulozik
U
U
Food Process Engineering and Dairy Technology, Technische Universität München Weihenstephaner Berg 1, Freising, Germany.
D003890:Desiccation; D005285:Fermentation; D005516:Food Microbiology; D007778:Lactobacillus / Q000187:drug effects* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D050296:Microbial Viability; D019936:Probiotics; D013012:Sorbitol / Q000494:pharmacology*; D014618:Vacuum
D013012:Sorbitol