|Gharst, Greg - NC STATE UNIVERSITY|
Submitted to: Journal of Texture Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 2006
Publication Date: November 30, 2006
Citation: Davis, J.P., Gharst, G.A., Sanders, T.H. 2006. Some rheological properties of aqueous peanut flour dispersions. Journal of Texture Studies. 38(2): 253-272. Interpretive Summary: Peanut flours are commercially available food ingredients prepared from partially defatted whole peanuts. There is no published data pertaining to the fundamental rheological properties of peanut flours. Accordingly, the goal of this work was to characterize the rheology of aqueous dispersions prepared from peanut flours. Peanut flours varied according to roast intensity (light or dark) and residual oil content (12 or 28%). Higher oil contents negatively impacted the capacity of the flours to thicken. A slight roast effect was detected, with darker roast flours thickening less effectively than light roast flours. The incorporation of peanut flours into foods such as protein bars, confections, baked goods, etc. is expected to considerably affect product texture. Product texture is in turn closely related to the rheology of the food and its individual ingredients, meaning this data should aid those optimizing the texture of foods containing peanut flours.
Technical Abstract: The rheological behaviors of aqueous peanut flour dispersions were characterized across a range of conditions, including controlled heating and cooling rates under both large and small-strain deformations. Fat content of the dry flours influenced rheological characteristics, as dispersions of higher fat flours formed gels (small-strain) or thickened (large-strain) less efficiently than lower fat flours. A roast effect was also apparent, especially for dispersions of the higher fat flours in which light roast flours thickened more effectively than dark roast flours. When compared to dispersions of toasted soy flour at equivalent total solids concentration, peanut flour dispersions were less viscous at lower temperatures (< 75°C), but at higher temperatures, the low fat peanut flour dispersions formed gels that were more rigid than soy. Centrifugal separation of the peanut flour dispersions revealed that the insoluble material of the dispersions most significantly contributed to the observed rheological responses. SDS-PAGE was used to characterize the soluble and insoluble proteins making up the various dispersions. Comparison of the banding patterns for the various peanut flours with non-roasted peanut protein found increased smearing within the peanut flour proteins (both soluble and insoluble), which is attributed to the Maillard reaction. Electrophoretic patterns for the soluble and insoluble fractions were different, with increased smearing in the high MW region for insoluble fractions and increased smearing in the low MW region for the soluble proteins. SDS-PAGE results are discussed in terms of observed rheological phenomena.