Résumé:
Galactomannans are the main components of locust bean gum issued from the fruit of the carob tree Ceratonia siliqua L; and represent a stored form of polysaccharides found in the translucent endosperm of seeds. They are well known as best thickening gels and are therefore widely used as a natural food additive (E410) in many food preparations, pharmaceuticals and cosmetics. In the present study, we aim to explore the gelling property of carob galactomannans when used for the microencapsulation of lactic acid bacteria in order to protect them from the negative effects of in vitro simulated digestive conditions. Two beneficial bacteria were used: Bifidobacterium animalis subsp lactis Bb12 and Lactobacillus rhamnosus LBRE-LSAS. Survival of free or encapsulated cells in galactomannan carob gel used alone or combined with sodium alginate, carrageenan or xanthan, was determined after exposure to the in vitro simulated gastrointestinal conditions (gastric condition: pH 2, pepsine 3 g/L, intestinal condition: bile 0.3%: W/V, pH 6.5). The obtained results have shown that survival of the two beneficial bacteria was significantly improved when encapsulated in gel carob made of galactomannans alone or combined with sodium alginate, carrageenan or xanthane. The best protective effect of cells against digestive hostilities was observed when galactomannans were combined with xanthan. There is no a such protective effect if carob galactomannans are used alone since viable cell count required was less than 106/mL which is the less required level to allow beneficial cells exhibit their health effect in the digestive environment. The optimal combination giving rise to the best protective effect of beneficial bacteria studied is that of galactomannans (1.8%) and sodium alginate (1.2 %).
