Date yogurt supplemented with Lactobacillus rhamnosus (ATCC 53103) encapsulated in wild sage (Salvia macrosiphon) mucilage and sodium alginate by extrusion: The survival and viability against the gastrointestinal condition, cold storage, heat, and salt with low pH

Abstract

The efficacy of probiotics in providing health benefits may be related to their ability to survive at a sufficient concentration of 10⁶ CFU/g during storage in food and colonization in the gastrointestinal tract. Microencapsulation is a viable method to improve the survivability of probiotics under harsh environmental conditions. In this research, microencapsulated Lactobacillus rhamnosus (MLR) was produced by a two-layer extrusion technique with sodium alginate and wild sage (Salvia macrosiphon) mucilage (SMM) in varying concentrations ranging from 0.2% to 0.8% as the first and second wall materials, respectively. The microencapsulation efficiency and second layer diameter of beads increased significantly with the increase in SMM concentrations. Microencapsulated Lactobacillus rhamnosus (LR) maintained its minimal concentration (6 log CFU/g) during 9 min at 72°C. The MLR-date yogurt (DY) sample had the lowest pH, highest acidity, and highest survival rate among the others at the end of storage. In simulated gastrointestinal conditions (SGC), the survival rates of free LR (FLR) and MLR were 45% and 47% on the 14th day of storage, respectively. In sensory properties, MLR had the highest score in odor and texture parameters but not in others. The MLR viscosity (666.3 mPa·s^-1) and SEM images show a relatively denser structure for MLR. In conclusion, this study emphasized the potential of using double-layered beads to protect probiotics, providing valuable inspiration for developing new functional foods with higher survival ability in harsh conditions.

Keywords: Lactobacillus rhamnosus; Salvia macrosiphon; extrusion; heat stress; simulated gasterointestinal condition.

FIGURE 1

Photography image of microencapsulated Lactobacillus rhamnosus (MLR) from left to right, at concentrations of 0.2, 0.4, 0.6, and 0.8 percent (a–d) with Salvia macrosiphon mucilage (SMM), respectively (top row); and light microscopy of MLR from left to right, at concentrations of (0.2, 0.4, 0.6, and 0.8) percent (e–h) with SMM, respectively, used in microencapsulation (40×) (middle row). Scan electron microscopy of microencapsulated Lactobacillus rhamnosus (MLR) from left to right at concentrations of 0.2, 0.4, 0.6, and 0.8 percent (i–l) with S. macrosiphon mucilage (SMM), respectively (bottom row).

FIGURE 2

The free Lactobacillus rhamnosus (FLR) and microencapsulated Lactobacillus rhamnosus (MLR) in different concentration (0.2, 0.4, 0.6, and 0.8%) of Salvia macrosiphon mucilage (SMM) survive at 72°C (a) and during storage at 4°C (b). The data (mean ± standard deviation) are from three replications. Means with different lowercase letters had a significant difference (p ≤ .05) by the Duncan test.

FIGURE 3

Acidity (a) and pH (b) of free Lactobacillus rhamnosus (FLR), microencapsulated Lactobacillus rhamnosus (MLR) and control C date yogurt during storage time.

FIGURE 4

The survival of Lactobacillus bulgaricus (L.blu), Streptococcus thermophilus (S.t), and Lactobacillus rhamnosus (LR) in control‐date yogurt (DY) (C‐DY) (a), DY contains free Lactobacillus rhamnosus (FLR‐DY) (b), and DY contains microencapsulated Lactobacillus rhamnosus (MLR‐DY) (c) during storage time. The survival of FLR and MLR in date yogurt during simulated gastrointestinal conditions at 1st and 14th days (d) of storage. Data (mean ± standard deviation) are from three replications. Lowercase letters (a–f) show significant differences (p ≤ .05) among samples in each parameter during storage time.

FIGURE 5

Sensory properties of control (c); microencapsulated Lactobacillus rhamnosus (MLR) and free Lactobacillus rhamnosus (FLR) during storage time in date yogurt. Sensory parameters consist of odor (a); consistency (b); flavor (c); and color (d). Data (mean ± standard deviation) are from three replications. Lowercase letters (a‐b) show significant different (p ≤ .05) among samples in each parameter during storage time.

FIGURE 6

Relationship between viscosity (mPa/s) and shear rate (1/s) (a); shear rate (1/s) shear stress [Pa] (b) in control C; microencapsulated Lactobacillus rhamnosus (MLR); and free Lactobacillus rhamnosus (FLR) in the 28th day of storage time of date yogurt.

FIGURE 7

The SEM image of date yogurt contains microencapsulated Lactobacillus rhamnosus (MLR), free Lactobacillus rhamnosus (FLR), and control C, during storage time. C in 1st (a); FLR in 1st (b); MLR in the 1st (c); C in the 28th (d); FLR in the 28th (e); and MLR in the 28th (f) days of storage period.