Micro-encapsulation of Bifidobacterium lactis for incorporation into soft foods

Abstract

Micro-encapsulation of the probiotic micro-organism Bifidobacterium lactis isolated from a bio-yoghurt starter culture, was carried out using a mixture of hydrated gellan and xanthan gums. Rheological studies showed that the gum mix was suitable for encapsulation of B. lactis, for incorporation into soft foods/beverages. The gel behaved as a non-Newtonian material, and the flow curve fitted well to the Herschel-Bulkley model. The average yield stress of the gum was 1.515 Pa, indicating gum stability, and the yield stress range was 1 Pa over a temperature range of 35-50°C. Almost constant minimum gum viscosity occurred between 46 and 61°C. Oval/round capsules were synthesized manually using a monoaxial gum flow through a 27.5 G bevelled needle, together with a superposed air stream (air knife technique). The diameter of the capsules, measured using laser diffractometry, varied from 20 to 2200lm, with 50% of the capsules having a diameter of £637 lm. Numbers of viable B. lactis in the capsules were estimated using high power ultrasound (20 kHz). By using a concentrated inoculum of B. lactis, microcapsules containing log 10 11-12 c.f.u. g )1 were synthesized. Apart from the anaerobic culturing of B. lactis, all other work was done in the presence of atmospheric oxygen. The organism exhibited a high degree of oxygen tolerance. A 21-day survival study of immobilized cells in 1 M sodium phosphate buffer (pH 7) stored at either 4 or 22°C indicated that B. lactis survived in excess of log 10 11 c.f.u. g )1 microcapsule. This technique represents a suitable means of supplying viable probiotics to the food and/or pharmaceutical industries. Mathematical symbolsHerschel-Bulkley model: s 0 ¼ s y À j Àn y s 0 yield stress s y shear stress j y fluid consistency index n flow behaviour index

Microencapsulated probiotics using emulsification technique coupled with internal or external gelation process

“…Microcapsule size distributions with a very wide range have been reported by several researchers and the optimum microcapsule size is a compromise between the effectiveness of encapsulation and the sensory properties (Arup et al, 2011). A minimum diameter of 100 m has been suggested to offer better protection in gastric juice, and an optimum range of 100-200 m has been proposed (McMaster, Kokott, & Slatter, 2005). The mean diameter of our emulsification/internal gelation beads was just within this limit.…”

Technology and potential applications of probiotic encapsulation in fermented milk products

“…Higher than 10 6 cfu mL −1 (McMaster et al, 2005) Sodium alginate with poly-L-lysine or chitosan (Extrusion technique)…”

“…Gellan gum is a microbial polysaccharide derived from Pseudomonas elodea and is constituted of a repeating unit of four monosaccharide molecules (glucose, glucuronic acid, glucose and rhamnose). Several investigations have reported the combination of gellan and xanthan as microencapsulating materials (Muthukumarasamy et al, 2006;McMaster et al, 2005). The combination of xanthan and gellan gums to form bead is not only acid resistant but also is stabilized by calcium ions which may protect probiotic cells from acid injury.…”

“…The shape and size of capsules affecting the sensory quality of final products are important issues for industrial production. Furthermore, in spray-drying process, the outlet temperature may affect the colour of the capsules due to a Maillard reaction (a form of non-enzymatic browning similar to caramelization) (McMaster et al, 2005;O′Riordan et al, 2001;Su et al, 2007). The addition of encapsulated probiotic bacteria did not significantly change the appearance and color, acidity, flavor, or aftertaste of the yoghurts, but significantly affected their textural properties (smoothness) (Krasaekoopt et al, 2006).…”

Transglutaminase-induced caseinate gelation for the microencapsulation of probiotic cells

“…Faergemand et al (1997) found that incubation of sodium caseinate with TGase only slightly influences its emulsifying properties. The optimal size for microcapsules containing probiotics depends, however, on the intended purpose and on the type of food (McMaster et al, 2005). While 1% capsules with diameters between 2 and 3 mm could not be sensorily detected in salami , capsules of that size range give an adverse sensorial effect in yoghurt, milk and sour cream (Hansen et al, 2002).…”