Physicochemical and structural characterization of resistant starch isolated from Vigna unguiculata

• Published in: International journal of biological macromolecules 2020-03, Vol.147, p.268-275
• Main Authors: Rengadu, Danielle, Gerrano, Abe S., Mellem, John J.
• Format: Article
• Language: English
• Subjects: Cowpea; Resistant starch; Simulated digestion
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2020.01.043

In this study, characterization was conducted on resistant starch, isolated from different cultivars of V. unguiculata (Bechuana White, Fahari, PAN 311, TVU 11424 and DT 129-4). The fraction of resistant starch obtained was found in the range of 9.42–13.74%, with DT 129-4 yielding the highest fraction. Amylose content of the starches varied between 18.72 and 19.67%. Swelling power, solubility index and syneresis was directly proportional to the different temperatures. A correlation between amylose content and swelling power was observed as swelling power was indirectly proportional to amylose content. Water and oil absorption capacity was 31.93–88.06% and 10.29–27.71% respectively. Foaming, emulsion capacity, and stability were done, however, due to the lack of protein in the resistant starch samples, results obtained were relatively low, ranging between 0.00 and 22.41%. The degree of whiteness during colour analysis ranged between 80.81 and 84.61%. The FTIR-spectra displayed no distinctive difference amongst the vibration bands on the hydroxyl, methine and carbonyl frequency stretches and confirmed the polysaccharide nature of the resistant starch. The XRD spectra displayed a Ca-type crystalline structure for all 5 cultivars. Overall, this study shows that resistant starch has the potential to be used in many food applications and as a microencapsulation membrane. •Vigna unguiculata cultivars contain approximately 9–14% resistant starch.•Swelling power of resistant starch is indirectly proportional to amylose content.•Resistant starch displayed a Ca-type crystalline structure.•Resistant starch has the potential to be used in various food applications.