Impact of formulation on high-protein bar rheological and wear behaviors.

Due to the popularity of high-protein bars, many new formulations are being generated to meet consumer preferences. New formulations may have different mechanical behaviors that can negatively impact processing ability, which makes determining the effect of ingredients on processing ability important. Thus, the objective of this study was to determine the effects of major ingredients in high-protein bars on their rheological and tribological behaviors. Two response surface designs of model high-protein bars comprising whey protein isolate (WPI), high-fructose corn syrup (HFCS), and either canola oil (first design) or vegetable shortening (second design) were evaluated. Rheological tests, including adhesion, strain and frequency sweeps, large amplitude oscillatory shear, and wear testing, were conducted to determine the impact of individual ingredients on high-protein bar mechanical behaviors. Oil-based formulations had greater adhesion at higher levels of HFCS, while shortening-based formulations were affected by WPI more than HFCS, resulting in lower overall adhesive maximum forces. Formulas with higher levels of WPI had lower phase angles and greater extent of nonlinear viscoelastic and strain-hardening behaviors, while formulas with higher lipid and HFCS levels had higher phase angles. Overall, ingredient ratios had a notable impact on both oil- and shortening-based high-protein bar rheological and wear behaviors, suggesting that rheological and tribological testing could be useful for indicating processing ability of high-protein bars. The information gained in this study can be used by food manufacturers that produce cold-extruded or laminated food products. The results can help predict the ability of various formulations to be successfully processed, decreasing product development, and reformulation time and expense.