Microstructural study of air-drying kinetics of Ca(II)-alginate beads to preserve cowpea extracts.

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

Campinhas

Congreso; 31st RAU Annual Users Meeting LNLS CNPEM; 2021

The great potential of Ca(II)-alginate beads in preserving biomolecules and their use as a carrier of bioactive compoundshas been demonstrated. However, several food applications require long-term storage and thus, numerous preservationtechniques such as drying have been applied. Still, research of stability of bioactive compounds in these treatmentsfocus on the morphology of the beads and the microstructure of the network but do not consider the microstructuralchanges that occur during the drying process.Ca(II)-alginate beads were prepared to preserve phenolic compounds extracted from cowpea (Vigna unguiculata) byproducts by using high-intensity ultrasound (VCX500, Sonics, US). Also, the influence of the addition of cowpea isolatedproteins as an excipient of the beads has been analysed. The microstructural changes of the network during air-dryingtreatment have been studied by SAXS at the LNLS SAXS1 beamline in Campinas, Brazil at λ = 0.1488 nm. The wavevector (q) was selected in the range 0.142 nm−1 < q < 5.035 nm−1. All the Ca(II)-alginate beads analysed showed isotropicscattering and were modelled as a fractal system composed of rod-like structures.Significant differences were observed between the alginate beads containing the whole extract with respect to thosecontaining cowpea isolate protein, revealing that cowpea protein is embedded within the rods, obtaining thicker butless dense rods disposed in a more disordered structure. These differences remained constant until 60 min of the airdrying treatment at 25 ℃ (even with moisture losses up to 30%). From this time, the microstructure of the dried beadsat the final stage if drying (xw = 0.5 kgw/kgT) showed the loss of the typical scattering of rod-like structures and evendisplayed new signals at high q in the presence of cowpea proteins.