Authors: Lawrence A Arogundadea, Catherine O. Eromosele, lghodalo C. Eromosele, Oladipo Ademuyiwa
LWT – Food Science and Technology 44 (2011) 524 – 534
Abstract
The rheological characterizations of African yam bean (Sphenostylis stenocarpa) protein dispersions were investigated. lsoelectrically precipitated protein-IPalk and IPsalt isolates
obtained from alkaline and salt extractions respectively were more soluble than caldum predpitated proteins (CaPaik and CaPsalt pH 3, 7 and 8. Regression analysis showed that Power law, Casson and Bingham rheological models adequately desaibed rbeological behaviors of S.stenocarpa protein dispersion. However, Power law gave the best fit The flow behavior indices (n), at different ionic strength, pH, and temperature media were less than unity, indicating that S. stenocarpa protein dispersion exhibited pseudoplastic behaviors under the conditions tested. Salt extracted proteins were more pseudoplastic than alkali extracted counterpart with n for salt extracted proteins (IPsalt & CaPsalt) lower than that of alkali extracted protein (CaPalk& CaPsalt. This is a numerical indication that salt extracted S. stenocarpa proteins were of larger shear- thinning tendency than the alkali extracted proteins. The consistency coeflidents, k of isoelectrically precipitated protein (0.305-0.327 Pas”) were significantly (P < 0.05) higher than that of calcium proteinates in the range ranged 0.167-0.180 Pas”. Both isoelectrically precipitated proteins and calcium proteinates exhibited yield stress, however, isoelectrically precipitated S. stenocarpa protein exhibited significantly (P < 0.05) higher yield stress (0275-0308 Pa) than the calcium proteinates (0.148 -0.165 Pa). The effect of temperature on apparent viscosity of the proteins was evaluated using an Arrhenius-type equation. The activation energies (EJ obtained were in the range 33-512 and 42.6 -55.51mol 1 for calcium proteinate and isoeIectricaIIy precipitated protein respectively.