Physico-chemical and functional properties of cowpea protein isolate as affected by the dehydration technique

Cowpea protein isolate (CPI) was extracted through salt assisted extraction technique and dehydrated by freeze drying, spray drying and vacuum drying. The effect of dehydration technique for preparation of cowpea protein isolate powder on the nutritive and functional properties was investigated. The x-ray crystallography, phase transition analysis and surface morphology established the variation in the agglomerates and nature of the particles formed upon dehydration. Freeze-dried and spray dried powders displayed least gelation capacity at 8% compared to 12% for vacuum dried isolates besides higher gel strength. The crossover point of storage and loss modulus for freeze-dried CPI was observed much earlier than for the spray and vacuum dried CPI. The emulsion capacity and creaming stability indices for freeze dried CPI were higher. Vacuum dried samples however showed highest emulsion activity index (94.88 m²/g) and good foaming ability (88.89%). Thus depending on the functional attribute intended for end-use, the most economic drying method can be considered as reasonable option for converting the protein isolates into powders.