Galacto-oligosaccharides as protective agents in the preservation of Lactobacillus delbrueckii subsp. bulgaricus

SANTOS MAURICIO; TYMCZYSZYN E,; GERBINO, E.; SOSA NATALIA; ARAUJO-ANDRADE C.; SCHEBOR C.; GOMEZ ZAVAGLIA, A.

Pornichet

Congreso; New frontiers in Anhydrobiosis; 2014

The important role of lactic acid bacteria as starters in the elaboration of dairy products highlights the need of both appropriate preservation and reliable evaluation. Freeze-drying is one of the most common procedures for starter preservation. However, the decrease of water activity is responsible for a dramatic reduction in viability. To avoid this, the use of protective agents is mandatory. Polyhydroxylated compounds, such as sucrose and trehalose, have been used consistently as protectants. The formation of glasses in the dried state, in which biochemical reactions are considerably retarded, has been proposed to explain their protective capacity. The goal of this work was to investigate the efficiency of galacto-oligosaccharides (GOS), widely known as prebiotics, to protect Lactobacillus delbrueckii subsp. bulgaricus during freeze-drying. Lactobacillus delbrueckii subsp. bulgaricus CIDCA 333 was freeze-dried in the presence of GOS. Samples were stored at relative humidities (RH) ranging 11-80%. Survival of microorganisms was assesed by plate counting and by near infrared spectroscopy (NIR). Storage at 32, 20 and 4ºC was investigated by plate counting during 45 days. The correlation between molecular mobility [as measured by Proton nuclear magnetic resonance (1H NMR)] and loss of viability explained the efficiency of GOS to preserve L. bulgaricus. The preservation of microorganisms was improved at low molecular mobilities and this condition was obtained at low water contents and low storage temperatures. NIR resulted a useful tool to assess bacterial viability and amorphous-rubbery transitions of freeze-dried samples stored at different RHs.