High-intensity ultrasound-assisted extraction of phenolic compounds from cowpea pods and its encapsulation in hydrogels

TRAFFANO-SCHIFFO, MARIA VICTORIA; AGUIRRE CALVO, TATIANA ROCIO; AVANZA, MARÍA VICTORIA; SANTAGAPITA, PATRICIO R.

Heliyon

Elsevier

Año: 2020 vol. 6

2405-8440

Currently and according to the growing worldwide interest in the revaluation of agricultural by-products, the useof legumes waste presents great potential to obtain bioactive compounds. In this context, an extract rich inphenolic compounds was obtained from Vigna unguiculata (cowpea) pods by optimizing the high-intensity ultrasoundconditions (10 min and 36% of amplitude) using response surface methodology. Then, the extract wasencapsulated in Ca(II)-alginate beads with the addition of arabic or guar gums or cowpea isolated proteins. Acomplete morphological study by image analysis and microstructural evaluation by SAXS has been carried out.Results showed that beads containing alginate and alginate-guar gum have the highest loading efficiency of totalphenolic compounds (47 %) and antioxidant activity (44 %). However, the coupled effect of the cowpeaextract and the isolated proteins (at it higher concentration) increased the antioxidant capacity of the beads due tothe contribution of the phenolic compounds and the amino acids with anti-radical activity, reaching a value of 67 % of inhibition of ABTS. Finally, the microstructural analyses revealed that cowpea pod extract increasedthe interconnectivity of the rods due to the presence of trivalent cations, conferring versatility, and larger coordinationto the network. Also, it was observed that the addition of cowpea proteins produced more interconnectedbigger and fewer compacts rods than beads containing only alginate, increasing 12 and 49 % theinterconnection and the size, respectively, and decreasing 10 % their compactness. This research demonstratedthe use of cowpea sub-products as a source of bioactive compounds that further modulate the microstructure ofthe hydrogel network, and the outstanding potential for being incorporated in techno-functional foods by usingCa(II)-alginate as a carrier.