Cruciferin improves stress resistance and simulated gastrointestinal survival of probiotic Limosilactobacillus reuteri in the model encapsulation system

Abstract

Encapsulation is a viable strategy to improve the stability and survival of probiotics during processing, storage, and consumption. Cruciferin, a major canola protein with high denaturation temperature and resistance to gastric degradation, has potential for encapsulation and protection of probiotics against harsh conditions in processing and gastrointestinal tract. Cruciferin/alginate capsules were fabricated to encapsulate probiotics, and were characterized using confocal and scanning electron microscopy (SEM). The bacterial viability was studied during storage, processing, and gastro-intestinal transit. Limosilactobacillus reuteri TMW 1.656 was encapsulated in spherical cruciferin/alginate capsules (2.2 ± 0.1 mm) prepared using an extrusion method. SEM images of the capsules showed that the bacteria were entrapped within the porous structure which was formed by the complexation of cruciferin and alginate. The confocal microscopy images confirmed that cruciferin and alginate were homogeneously distributed throughout the capsules. The shelf life of the bacteria in the presence of cruciferin and alginate increased up to 8 weeks at 4 °C, while unencapsulated (free) bacteria lost their viability after 2 weeks storage. The heat resistance of encapsulated bacteria exposed to 65 °C and 70 °C was improved by up to ∼ 4 and 2 log cycles, respectively, compared to unencapsulated bacteria. Encapsulation also protected L. reuteri against gastric low pH and enzymes; the viability was 3 logs higher when compared to unencapsulated bacteria. The capsules were degraded in simulated intestinal fluid, leading to the release of the encapsulated bacteria, whereas the wall materials increased the resistance of released bacteria to bile salts. Comparison between the viability of unencapsulated bacteria in presence of cruciferin/alginate mixtures and bacteria encapsulated in the capsules revealed that capsule formation provided physical barriers to the harsh conditions and played a key role in the protection of bacteria. This study showed that cruciferin/alginate capsules are capable to improve stability and shelf life of Limosilactobacillus reuteri.