Nonlinear (Large-Amplitude Oscillatory Shear) Rheological Properties and Their Impact on Food Processing and Quality.

Large-amplitude oscillatory shear (LAOS) testing has been increasingly used over the past several decades to provide a fuller picture of food rheological behavior. Although LAOS is relatively easy to perform on a wide variety of foods, interpretation of the resulting data can be difficult, as it may not be possible to link the results to food components, microstructural features or changes, or physicochemical properties. Several analysis methods have been developed to address this issue, but there is currently no standard method for foods. In food research, LAOS has mainly been used to investigate connections between food microstructures and rheological behaviors, although there have been some studies on connections between food LAOS behaviors and processing or sensory behaviors. LAOS has the potential to be a valuable tool for investigating food structure-function-texture relationships, but much work remains to develop these relationships, particularly in the area of connecting LAOS to sensory attributes.

Understanding How High-Protein Bar Formulations Impact Their Mechanical and Wear Behaviors Using Response Surface Analysis.

High-protein bars are popular snack items that can have significant processing issues like sticking, clogging, and cold flow. These issues are primarily problematic during formulation development because current predictive testing is reliant on highly empirical bench tests or pilot plant testing, which is expensive and time-consuming. Wear testing, which has been used in the medical field to evaluate the lifetime of soft materials used in joint replacements, may have promise in evaluating food processing ability. Wear and rheological testing were used to better understand high-protein bar processing ability. The objective of this study was to determine bench-level instrumental tests that would be able to predict processing ability for a given formulation. Two response surface designs were used for formulations of model bar systems comprising whey protein isolate (WPI), high fructose corn syrup (HFCS), and either canola oil or vegetable shortening. Ingredient formulation affected processing ability, wear behaviors, and rheological behaviors. Formulations with high ratios of WPI to HFCS and either shortening or oil exhibited good processing ability, lower wear rates, and increased elastic-type behavior, indicating that processing ability is related to formulation. The results of this study indicated that material mechanical and wear behaviors were related to processing ability; both were controlled by formulation. Because it was shown to be a good indicator of high-protein bar processing ability, wear testing of food has potential significance in benchtop testing. PRACTICAL APPLICATION: Understanding of how high-protein bar formulations impact their mechanical behaviors can help streamline their formulation development and scaling from bench to industrial production. Processing ability may be predicted with a quick wear test, providing a rapid testing method that requires little sample for evaluating bar formulations.

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.

Rheological and sensory behaviors of parboiled pasta cooked using a microwave pasteurization process.

Pasta hydration and cooking requirements make in-package microwave pasteurization of pasta a processing challenge. The objective of this study was to assess instrumental and sensory attributes of microwave-treated pasta in comparison to conventionally cooked pasta. Fettuccine pasta was parboiled for 0, 3, 6, 9, or 12 min, pasteurized by microwaves at 915 MHz, then stored under refrigeration for 1 week. Pastas were evaluated by a trained sensory panel and with rheometry. Total pasta heat treatment affected both rheological and sensory behaviors; these differences were attributed to ultrastructure differences. Significant nonlinear behavior and dominant fluid-like behavior was observed in all pastas at strains >1%. Sensory results suggested microwave pasteurization may intensify the attributes associated with the aging of pasta such as retrogradation. A clear trend between magnitude of heat treatment and attribute intensity was not observed for all sensory attributes tested. The microwave pasta with the longest parboil time showed rheological behavior most similar to conventionally cooked pasta. Principal component analysis revealed that no microwave-treated pasta was similar to the control pasta. However, pasta parboiled for 9 min before microwave treatment had the greatest number of similar sensory attributes, followed by pasta parboiled for 6 or 12 min. Further study is needed to determine overall consumer acceptance of microwave-treated pasta and whether the differences in sensory and rheological behavior would impact consumer liking. PRACTICAL APPLICATIONS: The results of this study may be applied to optimize microwave pasteurization processes for cooked pasta and similar products, such as rice. The measurement and analysis procedures can be used to evaluate processing effects on a variety of different foods to determine overall palatability.