No abstract

SummaryThere has been growing interest in the use of resistant starch (RS) as a prebiotic for physiological benefits and to reduce the risk of chronic diseases. In this study, RS was isolated from samples of five cowpea cultivars (DT129‐4, TVU 11424, PAN 311, Fahari and Bechuana White) seeds to determine their potential prebiotic effects, and proximate and mineral composition. Results obtained showed samples of five cowpea cultivars to be high in protein (18.0–28.7%) and carbohydrates (54.9–66.0%) and low in fat (0.6–3.7%). The RS from cowpea samples ranged between 9.3 and 12.1% with cultivar DT129‐4 having the highest amount. Fermentation of RS using mixed and pure cultures was done, and bacterial growth was monitored over a 24‐h period. Resistant starch isolated from all cowpea samples fulfilled the criteria to be classified as a prebiotic which have a wide range of beneficial effects on the host, with cultivar DT129‐4 showing the most prebiotic potential amongst cowpea samples tested.

In this study, the viability and stability of probiotics (Lactobacillus casei and Bifidobacterium animalis) encapsulated in a resistant starch medium through freeze‐drying is evaluated. Particle size, SEM, and color analysis are done on the microcapsules. The encapsulation yield after freeze‐drying is between 81.55% and 88.78%, with viability of the microcapsules analyzed in simulated gastric juice (SGJ) and simulated intestinal juice (SIJ) as well as in apple juice store at 4 °C over 28 days. The microencapsulated probiotics in this study has a substantial final count for SGJ and SIJ between 7.30–7.98 Log colony‐forming unit (CFU) mL‐1 and 7.26–7.89 Log CFU mL‐1, respectively. The Log CFU mL‐1 for free cells are significantly lower than the microcapsules. The final viability for microcapsules in the juice at the end of 28 days for resistant starch + L. casei (RSL), resistant starch + B. animalis (RSB), and resistant starch + L. casei + B. animalis(RSLB) are 7.53, 6.98, and 7.46 Log CFU mL‐1. This confirms that microencapsulation enhance the survival of L. casei and B. animalis in fruit juice under cold storage. Results from this study show that resistant starch has potential as an encapsulating material as it protected the probiotic cells in conditions such as freeze‐drying, simulated gastrointestinal digestion and low pH environments during beverage application.

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.