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Understanding the viscoelastic properties of peanut butter using controlled stress rheometry |
V. M. TOTLANI and M. S. Chinnan. Department of Food Science and Technology, University of Georgia, 1109, Experiment Street, Griffin, GA 30223-1797 Peanut butter exhibits viscoelastic behavior due to the network formed by the peanut solids with the added stabilizer. Rheological characterization of peanut butter may aid in monitoring network formation and matrix strength evaluation of the product. The objective was to investigate the viscoelastic nature of peanut butter using controlled stress rheometry. Stabilized (Kroger® creamy) and unstabilized butter (Kroger® natural) were subjected to time and oscillatory stress sweeps, and creep tests at various temperatures (5, 10, 15, 20, 25, 26, 35˚C) using AR1000, TA instruments Inc. with 40mm parallel plate geometry. The gap was set at 1000µm and 2000µm, respectively for stabilized and unstabilized samples. The percentage strain applied for time sweeps were: 0.02% at 5˚C, 0.016% at 10 and 15˚C and 0.01% for >15˚C. At 5˚C, both stabilized and unstabilized samples were subjected to 1-900Pa of oscillatory shear stress for identifying the linear viscoelastic range (LVR) while at higher temperatures, 1-50Pa and 1-600Pa values were employed for unstabilized and stabilized butters, respectively. Creep tests were conducted within the LVR of each sample at a given temperature. Stabilized butter demonstrated viscoelastic nature at all temperatures and its creep-recovery response was explained by the presence of elastic compliances (Ji; i=2 to 4). The critical shear stress for stabilized butter was 100Pa at 5˚C and 35˚C, however, the storage modulus decreased sharply outside the LVR, with increased temperature. Unstabilized peanut butter was only able to show viscoelastic nature at 5˚C and exhibited inconsistent response and absence of structure at higher temperatures. Controlled stress rheometry can be applied as a tool to measure matrix strength and viscoelasticity of peanut butter, which can lead to evaluation of long term stability of the product.
Session 42, Food Engineering: Rheology and texture
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