Physicochemical and functional properties of starch from under‐utilized yam (Dioscorea spp) and cocoyam (Xanthosoma maffa (Scoth)) tubers of Southeast Nigeria
2016
Ukom, Anthony N. | Ojimelukwe, Philippa C. | Emetole, John M.
Physicochemical and functional properties of starches from some under‐utilized yam (D. cayenensis, D. dumetorum, and D. bulbifera) and cocoyam (X. maffa (Scoth) grown in Southeast Nigeria were determined. Analysis of variance showed that yam starches of D. cayenensis and D. bulbifera were characterized by large mean granule sizes (28 and 37.5 μm), high amylose content (37.8 and 35%), and high paste clarity (11.6 and 16%). Starches of D. dumetorum and cocoyam, X. maffa (Scoth), were characterized by smaller granule sizes (about 6 and 5 μm), low amylose content (11.2 and 13%), and low paste clarity (6 and 9.8%). The gelatinization enthalpy (ΔH) of D. cayenensis starch (16.7 j/g) was higher than the other tuber starches (about 12 j/g). Onset, peak, and end temperatures ranged from 73 to 81.3°C, 77.3 to 85.2°C, and 85.4 to 93°C, respectively, with X. maffa (Scoth) having the highest temperatures. The pasting temperatures ranged from 76 to 81°C. Hot paste, cold paste, and final viscosities were from 116.7 to 748 cP, 145.7 to 913.7 cP, and 156.7 to 966.3cP, respectively. D. bulbifera and D. cayenensis maintained higher viscosities than D. dumetorum and X. maffa (Scoth). Low paste clarity of D. dumetorum and X. maffa (Scoth) was associated with their small granule sizes and low amylose content. The physicochemical and functional properties of the yam and cocoyam tuber starches show that they can be used for specific food applications.
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