The effect of organic acids and storage temperature on lite salad dressing rheology and Zygosaccharomyces parabailii growth.

Zygosaccharomyces parabailii (Z. parabailii) causes spoilage in salad dressings due to its tolerance to osmotic pressure. The objective of this study was to determine the effect of organic acids and storage temperatures (4, 10, and 25 °C) on Z. parabailii growth and salad dressing mechanical properties. Acetic, lactic, and gluconic acids were used alone and in combination to acidify salad dressing. Z. parabailii-challenged formulations containing acetic acid alone tended to have lower counts of Z. parabailii when compared to Z. parabailii-challenged formulations containing other acid combinations. Overall, storage temperature had the most impact on Z. parabailii growth over a 45-day storage. Acidulant type and combination impacted salad dressing mechanical properties. During the 45-day storage period, all formulations showed increased viscosity, a Herschel-Bulkley viscosity profile, and elastic-dominant viscoelastic behavior. The degree of change in rheological behaviors over time was dependent on the type of acid used in the formulation. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05459-4.

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.

Relationships among rheological, sensory, and wear behaviors of cheeses.

Studying rheological and sensory behaviors of cheese provides structural and texture-related information that could be useful for a better understanding of the complex wear behaviors of cheese and their relationships with cheese industrial and oral processing behaviors. Thus, the objective of this study was to determine the relationships of rheological and sensory properties with cheese wear. Rheological tests including large amplitude oscillatory shear, strain sweeps at different temperatures (5, 15, and 25°C), and large-strain compression at room temperature (22 ± 2°C) were conducted for cheeses with varying fat contents (40, 50, 52, and 54% fat-in-dry-matter aged for different periods (15, 30, 45, and 60 d). Descriptive sensory analysis was used to evaluate cheese sensory texture attributes. Overall, fat content, testing temperature, and aging time had significant impact on cheese viscoelastic parameters. Higher temperature, aging time, and fat content led to lower rigidity and greater extent of nonlinear viscoelastic behaviors in the cheeses. Mass loss showed negative correlations with critical strain (γc ), critical stress (σc ), complex modulus (G* ), and fracture stress, but had positive correlations with phase angle (δ) and fracture strain. Sensory data showed that texture attributes were affected by cheese fat content and aging time and had significant correlations with mass loss at high normal force and sliding speed. This study showed that rheology and sensory data can be used to provide fundamental information on the wear behaviors of cheese and other soft materials.

Mechanisms of whey protein isolate interaction with basil seed gum: Influence of pH and protein-polysaccharide ratio.

In the present work, we determined the structure-function relationships of basil seed gum (BSG) and whey protein isolate (WPI) mixtures at the start of soluble complex formation, maximum soluble complex formation and predominant thermodynamic incompatibility to understand BSG:WPI blends interaction behavior. Accordingly, turbidity and zeta potential were analyzed in the pH range of 2.0-7.0 and BSG:WPI ratios of 1:4, 1:6.6 and 1:9. Dynamic rheometry was used to evaluate samples at three different pHs. Additionally, dilute solution properties of BSG, WPI and their blends were studied at pH = 7.0. Independent of mixture ratio, all dispersions showed maximum interaction at pH = 5.0, the start of soluble complex formation around pH = 6.0 and thermodynamic incompatibility interaction behavior at pH = 7.0. Cole-Cole plots based on dynamic rheometry supported the Gibbs free energy change of mixtures based on intrinsic viscosity data. These results are important to create new structures from mixtures of proteins and polysaccharides.

Interlaboratory Measurement of Rheological Properties of Tomato Salad Dressing.

Rheological properties of food materials are important as they influence food texture, processing properties, and stability. Rotational rheometry has been widely used for measuring rheological properties. However, the measurements obtained using different geometries and rheometers are generally not compared for precision and accuracy, so it is difficult to compare data across different studies. In this study, nine rheometers from seven laboratories were used to measure the viscosity and viscoelastic properties of a commercial salad dressing. The measurements were obtained at three temperatures (8, 25, and 60 °C) using different diameter parallel plates (20, 40, 50, and 60 mm). Generally, the viscosity measurements among rheometers differed significantly ( P < 0.05 ). For larger geometry diameter (40, 50, and 60 mm) and at lower temperatures (8 °C), viscosity measurements at lower shear rate (0.01, 0.1, and 1.0 s-1 ) were significantly different. Rheometer brand significantly affected storage modulus only at low (0.01%) and high levels (10% and 100%) of strain. Temperature was an influencing factor on viscoelastic behaviors only at high strain (>10%). Storage moduli values obtained by frequency sweeps were not affected by rheometer or plate diameter. Overall, rheometer, geometry, and temperature can influence rheological measurements and care should be taken when comparing data across laboratories or published works. Higher shear rates (≥10 s-1 ) and moderate strains (0.1% to 10%) generally provide more repeatable data among different laboratories. PRACTICAL APPLICATION: This study provides information on what factors may potentially influence rheological measurements conducted across different laboratories. It is useful for rheometer users who want to compare their experimental data to published data or compare two sets of published data. It is better to compare data collected at shear rates 10 s-1 and strains between 0.1% and 1.0%.

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.