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

MAURICIO SANTOS; E. ELIZABETH TYMCZYSZYN; ESTEBAN GERBINO; NATALIA SOSA; CUAUHTÉMOC ARAUJO-ANDRADE; CAROLINA SCHEBOR; ANDREA GOMEZ-ZAVAGLIA

Pornichet

Congreso; Workshop on molecular aspects of desiccation tolerance; 2014

The important role of lactic acid bacteria as starters in the elaboration of dairy products highlightsthe need of both appropriate preservation and reliable evaluation.Freeze-drying is one of the most common procedures for starter preservation. However, thedecrease of water activity is responsible for a dramatic reduction in viability. To avoid this, the use ofprotective agents is mandatory. Polyhydroxylated compounds, such as sucrose and trehalose, havebeen used consistently as protectants. The formation of glasses in the dried state, in whichbiochemical reactions are considerably retarded, has been proposed to explain their protectivecapacity.The goal of this work was to investigate the efficiency of galacto-oligosaccharides (GOS), widelyknown 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 wasassesed by plate counting and by near infrared spectroscopy (NIR). Storage at 32, 20 and 4ºC wasinvestigated by plate counting during 45 days. The correlation between molecular mobility [asmeasured by Proton nuclear magnetic resonance (1H NMR)] and loss of viability explained theefficiency of GOS to preserve L. bulgaricus. The preservation of microorganisms was improved atlow molecular mobilities and this condition was obtained at low water contents and low storagetemperatures. NIR resulted a useful tool to assess bacterial viability and amorphous-rubberytransitions of freeze-dried samples stored at different RHs.