Effect of encapsulation on the stability and survivability of Enterococcus faecium in a non-dairy probiotic beverage

Abstract

The main objectives of this work were to study the survivability of five probiotic lactobacilli strains in sour cherry juice and citrate buffer with similar pH values (pH 3.5) during storage at 4 ℃ as well as to encapsulate the strain with the least survival in calcium alginate beads. Enterococcus faecium from probiotic strains in sour cherry juice exhibited the least survival; therefore, this strain was selected for studying the protective effect of microencapsulation in calcium alginate beads. Microencapsulated probiotic cells were incorporated into sour cherry juice and then exposed to harsh conditions (e.g. heat treatment, low pH, and simulated gastrointestinal fluids). Changes in the probiotic survivability, pH and titratable acidity of sour cherry juice were monitored during 60 d. D-values of free cells, calculated at 60, 70 and 80 ℃, were 4.87, 1.48 and 0.43 min, respectively; while, those of microencapsulated cells were 9.41, 3.73 and 1.26 min, respectively. The decrease in the number of free E. faecium after exposure to low pH values (e.g. 2.5, 2 and 1.5) was 2.81, 3.74 and 4.18 log CFU/mL, respectively. Freshly prepared and 30-d old microencapsulated cells, maintained at 4 ℃ in sour cherry juice, showed 1.31, 2.13, 2.37 and 2.19, 2.46, 3.26 log CFU/mL reduction after exposure to similar pH conditions, respectively. The number of free and encapsulated probiotic cells after incubation in simulated gastric and gastrointestinal fluids was 5.86 and 4.81 and 8.05 and 6.61 log CFU/mL, respectively. The sensory attributes of probiotic sour cherry juice samples containing encapsulated cells were better than those fortified with free probiotics.

Keywords: gastrointestinal digestion; heat tolerance; microencapsulation.