Entrapment, survival and release of Bifidobacterium adolescentis within chickpea protein-based microcapsules

•Bifidobacterium adolescentis was entrapped within a chickpea protein-alginate capsule.•Capsules offered protection to B. adolescentis under simulated stomach conditions.•Capsules experienced burst-type release within simulated intestinal fluid.

Bifidobacterium adolescentis (ATCC 15703) was entrapped within microcapsules prepared using 10.00% (w/w) chickpea protein isolates cross-linked with 0.20% (w/v) of genipin, or in the presence of 0.20% (w/v) alginate or κ-carrageenan. After 2 h at pH 2.0/25 °C, B. adolescentis within the capsules prepared with genipin, alginate and κ-carrageenan were significantly (p < 0.05) reduced from ~ 8.0-8.5 log CFU mL− 1 to 1.8, 4.6 and 3.6 log CFU mL− 1, corresponding to D-values of 43.36 ± 7.50 min, 25.75 ± 0.47 min, and 32.23 ± 1.28 min, respectively. The volume mean diameter of formed protein capsules prepared with genipin, alginate and κ-carrageenan was 749.5 ± 2.3 μm, 21.9 ± 1.2 μm and 838.5 ± 31.3 μm, respectively. Capsules < 100 μm in diameter do not adversely affect sensory attributes, therefore only the chickpea protein-alginate design was tested further. The effect of alginate concentration (0.05, 0.10 and 0.20%, w/w) added to chickpea protein capsules were investigated for their ability to protect B. adolescentis. After 2 h at pH 2.0/25 °C, the viable cell numbers (log CFU mL− 1) decreased from ~ 8.0 to ~ 5.7 (D-value of 77.99 ± 6.93 min), ~ 6.4 (D-value of 185.50 ± 38.8 min) and ~ 4.6 (D-value of 43.36 ± 7.50 min) for chickpea protein with capsules with 0.05%, 0.10% and 0.20% (w/w) alginate, respectively. The number of surviving free and entrapped B. adolescentis cells after incubation in synthetic gastric juice at pH 2.5/37 °C revealed that encapsulation with 10% of chickpea protein-0.1% of alginate improved survival by 5.5 times, with D-values of 106.31 ± 17.03 min (entrapped cells) versus 18.98 ± 0.29 (free cells)) over 2 h. The release of encapsulated B. adolescentis within simulated intestinal fluid at pH 6.5⁄37 °C over 3 h indicated that after the first 5 min, almost all of the entrapped B. adolescentis (~ 7.8 log CFU mL− 1) cells were released, yielding free cell counts of ~ 7.1 log CFU mL− 1, followed by no further release. Encapsulation of B. adolescentis within chickpea protein-alginate microcapsules using emulsion technology allows probiotics to be protected against a simulated gastrointestinal environment, indicating their potential use in food and/or medical applications. Findings from this study suggest that chickpea protein-alginate capsule designs could serve as a suitable probiotic carrier intended for food applications due to its size (< 100 μm) and ability to protect acid-sensitive microorganisms under simulated gastric conditions.