Gellan Fluid Gel Embedded in Alginate Bead System: A New System for Encapsulation of Limosilactobacillus reuteri and Its Application in Sour Cherry Juice

Abstract

In the present research, we aimed to create a novel controlled-release device using two polymeric systems: beads of alginate hydrogel embedded with gellan fluid gel that contained Limosilactobacillus reuteri cells. Three different formulations, 1.5% alginate (Alg), 1.35%:0.15% alginate:gellan (Alg:Gel), and 1.2%:0.3% (Alg:Gel), were used in this research. We investigated the effect of this system on the physical properties of beads and probiotic viability, as well as application in sour cherry juice (for 8 weeks). The results showed that the presence of gellan fluid gel in the alginate microcapsules increased the hardness and diameter of the beads from 1.15 to 3.43 N and 1.71 to1.87 mm, respectively. Also, this system improved the viability of the microencapsulated bacteria under simulated gastrointestinal and thermal conditions (final counts of 7.17 and 7.00 logs CFU/mL, respectively). Regarding the probiotic viability during 28 days of storage (-18°C, 4°C, and 25°C), the counts of all treatments decreased during the storage, but the best results were observed at the freezing temperature (7.85 log CFU/mL). Raman confocal microscopy showed that the wall thickness of beads decreased by increasing gellan fluid gel from 10.3 to 8.6 μm. In the case of sour cherry juice, the viability of cells decreased in the range of 7.4-8.7 log CFU/mL, vitamin C in the range of 0.45-1.14 mg/L, and phenolic content in the range of 0.42-0.62 mg/L at the end of the storage period. As a result, the samples containing encapsulated L. reuteri, especially alginate/gellan fluid gel beads, showed better results. In summary, the beads made from 1.2% alginate and 0.3% gellan fluid gel proved to be an effective delivery and release system for L. reuteri cells and application in sour cherry juice.

Keywords: alginate; gastrointestinal condition; gellan fluid gel; probiotic; sour cherry juice.

FIGURE 1

Red map Z‐profile in 860–900 cm⁻¹, (a) alginate (1.5%, w/w) and (b) alginate:gellan fluid gel (1.2%:0.3%, w/w) beads.

FIGURE 2

Survival of free and encapsulated Limosilactobacillus reuteri (log CFU/mL) in different simulated gastrointestinal conditions (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparison of means using Duncan's multiple range test (p < 0.05).

FIGURE 3

Effect of heat treatment on viable counts of free and encapsulated Limosilactobacillus reuteri (log CFU/mL) (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparison of means using Duncan's multiple range test (p < 0.05).

FIGURE 4

Survival of free and encapsulated Limosilactobacillus reuteri (log CFU/mL) during storage at different temperatures: (a) 4°C, (b) 25°C, and (c) −18°C (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparisons of means using Duncan's multiple range test (p < 0.05).

FIGURE 5

The variation of (a) pH and (b) titratable acidity of different sour cherry juice samples (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparison of means using Duncan's multiple range test (p < 0.05).

FIGURE 6

The variation of total soluble solid (TSS) in different sour cherry juice samples (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparisons of means using Duncan's multiple range test (p < 0.05).

FIGURE 7

The variation of vitamin C content in different sour cherry juice samples (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparison of means using Duncan's multiple range test (p < 0.05).

FIGURE 8

Viability of free and encapsulated Limosilactobacillus reuteri (log CFU/mL) in sour cherry juice (4°C) (Alg, alginate; Gel, gellan fluid gel). Mean ± SD (n = 3); Statistical test: ANOVA and multiple comparison of means using Duncan's multiple range test (p < 0.05).

FIGURE 9

SEM images of (a, b) alginate (1.5%, w/w) and (c, d) alginate:gellan fluid gel (1.2%:0.3%, w/w) beads before (a, c) and after (b, d) of 8 weeks of storage in sour cherry juice (c: shows the particles of gellan fluid gel within the alginate bead).