SOME RHEOLOGICAL PROPERTIES OF AQUEOUS PEANUT FLOUR DISPERSIONS*

Abstract

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 changes, as dispersions of higher‐fat flours were less viscous than lower‐fat flours on an equal weight basis. A roast effect was also apparent, especially for dispersions of the higher‐fat flours in which light roast flours were more viscous than dark roast flours. Dispersions of toasted soy flour were more viscous at lower temperatures (<75C), but at higher temperatures, low‐fat peanut flour dispersions were more viscous than soy. Centrifugal separation revealed that the insoluble material of all dispersions primarily contributed to the observed rheological responses. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis was used to characterize the soluble and insoluble proteins making up the various dispersions, and these results are discussed in terms of observed rheological phenomena.PRACTICAL APPLICATIONSPeanut flour is a dry powder prepared after partial extraction of peanut oil from roasted peanut seed. This flour, as compared to peanut butter or whole peanut seed, has numerous functional advantages in formulated foods, including improved stability to lipid oxidation, an enriched protein content and the handling ease of a powder. However, there is no published fundamental rheological data pertaining to these ingredients. Accordingly, commercially available peanut flours with varying roast intensities and fat contents were rheologically characterized in aqueous dispersions, both in the absence and presence of heat. Residual fat content in the flours primarily affected rheological behaviors, with high‐fat flours being less viscous under equivalent conditions. A yield stress was observed in all dispersions held at 40C, which correlated with stability of the dispersion to particle settling. This data could ultimately aid texture optimization of products containing such flours.