Microencapsulation of Bifidobacterium animalis and Lactobacillus casei using resistant starch from Vigna unguiculata

Abstract

The use of functional foods is increasing globally with individuals aiming to maintain a healthy gut causing an increasing trend associated with probiotics in the health sector. Probiotics are live microorganisms that aid in improving the digestive system and gut health, however, the main problem associated with probiotics are ensuring a safe delivery through transition to the colon in harsh gastrointestinal conditions. For probiotics to be considered effective to the host a growth of Log 7 is essential in the colon, thus the need for microencapsulation. Therefore, this study was aimed at analysing resistant starch isolated from cowpea as an encapsulation material for Lactobacillus casei and Bifidobacterium animalis, for beverage application. Five different cultivars of cowpea (Bechuana white, Fahari, PAN 311, TVU 11424 and DT129-4) were analysed to determine the amount of resistant starch yielded as well as structural and physicochemical properties to determine the most suitable cultivar for the encapsulation process. The resistant starch percentage obtained was found in the range of 9.42-13.74%, with DT129-4 yielding the most resistant starch. The structural and physicochemical results obtained showed that the resistant starch isolated from cowpea has the potential for microencapsulation with cultivar DT129-4 exhibiting the most favourable results. Resistant starch was used as an encapsulating medium for Lactobacillus casei (RSL), Bifidobacterium animalis (RSB) and for a combination of the two probiotic microorganisms (RSLB) at a ratio of 1:1. The encapsulation yield after freeze drying were between 81.55-88.78% with the viability of the microcapsules under simulated gastrointestinal conditions also observed. The microcapsules were added to apple juice and the viability and stability of the microcapsules examined over 28 d. The final viability for microcapsules in the juice at the end of 28 d for RSL, RSB and RSLB were 7.53, 6.98 and 7.46 Log CFU/mL. This study shows that that resistant starch from cowpea has great potential as an encapsulating membrane within the nutraceutical beverage manufacturing industry.