The interaction between wheat and pea protein influences the final chemical and sensory characteristics of extruded high moisture meat analogs.

Plant-based meat analog products, including those produced by extrusion processing, have become increasingly popular. Complete comprehension of the texturization mechanism and the formation of fibrousness would help improve existing products and extend the variety of plant sources used. Therefore, this study aimed to provide improved insight into the mechanism of texturization during the processing of high-moisture meat analog (HMMA) products. Blends with different wheat and pea protein ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wheat:pea) were extruded at a screw speed of 400 rpm, two different moisture contents (50% and 55%), and a feed rate of 90 g/min using a co-rotating twin-screw extruder. Extrudates were analyzed for their texture, free sulfhydryl groups, disulfide bonds, and solubility in different extractants relative to the raw ingredient blends. In addition, a sensory analysis was conducted using the rapid and cost-effective "rate-all-that-apply" (RATA) methodology. The interplay between the two protein types had synergistic effects on the system parameters torque, pressure, and specific mechanical energy, as well as on some textural and sensory parameters. Molecular analyses were not influenced by the interplay between wheat and pea protein as the molecular analyses followed linear trends with the pea inclusion level. Analysis of protein solubility suggests that the texturization mechanism differs slightly depending on the protein type. It is suggested that the texturization of wheat protein depends highly on disulfide bonds, whereas the texturization of pea protein relies on the combination of disulfide bonds and non-covalent interactions. Additionally, RATA was found to be a valuable tool for HMMA products.

Impact of tamarind seed gum on the viscosity behavior, thermal properties, and extrusion characteristics of native corn starch.

Tamarind seed gum (TSG) is a cold-swelling hydrocolloid with remarkable processing stability and starch synergy. Its use in direct expanded extruded foods has not been documented. The thermal and pasting viscosity properties of six TSG (0%, 0.5%, 1.0%, 2.5%, 5.0%, and 7.5% TSG) and native corn starch blends were characterized by differential scanning calorimetry and ViscoQuick, respectively. These same blends were extruded using a corotating twin-screw extruder at four screw speeds (SSs) (150, 300, 450, and 600 rpm). System back pressure, motor torque, and specific mechanical energy (SME) were measured. Extrudate quality metrics, such as expansion ratio (ER), water absorption index (WAI), and water solubility index (WSI), were also measured. The pasting viscosities indicated that TSG inclusion increases viscosity but also makes the starch-gum paste more susceptible to permanent shear degradation. The thermal analysis indicated that TSG inclusion narrowed the melting endotherms and lowered the energy required for melting (p < 0.05) at higher inclusion levels. Extruder back pressure, motor torque, and SME decreased with increasing TSG levels (p < 0.05) as the TSG effectively lowered the melt viscosity at high usage rates. The ER reached a maximum of 3.73 with a 2.5% TSG level extruded at 150 rpm (p < 0.05). The WAI of extrudates increased with TSG inclusion rate at equivalent SSs, whereas WSI behaved oppositely (p < 0.05). Small inclusions of TSG can improve the expansion properties of starch, whereas larger inclusions result in a lubrication effect that mitigates the shear-induced depolymerization of starch. PRACTICAL APPLICATION: The impact of cold-water soluble hydrocolloids, including tamarind seed gum, on the extrusion process, is poorly understood. From this work, tamarind seed gum effectively modifies the viscoelastic and thermal characteristics of corn starch in a way that enhances the direct expansion characteristics of the starch during extrusion processing. The effect is more beneficial at lower gum inclusion levels as higher levels result in reduced capabilities to translate shear from the extruder into useful transformations of the starch polymers during processing. Small amounts of tamarind seed gum could be used to improve the quality of extruded starch puff snacks.

Temperature Gradient Approach for Rapidly Assessing Sensor Binding Kinetics and Thermodynamics.

We report a highly resolved approach for quantitatively measuring the temperature dependence of molecular binding in a sensor format. The method is based on surface plasmon resonance (SPR) imaging measurements made across a spatial temperature gradient. Simultaneous recording of sensor response over the range of temperatures spanned by the gradient avoids many of the complications that arise in the analysis of SPR measurements where temperature is varied. In addition to simplifying quantitative analysis of binding interactions, the method allows the temperature dependence of binding to be monitored as a function of time, and provides a straightforward route for calibrating how temperature varies across the gradient. Using DNA hybridization as an example, we show how the gradient approach can be used to measure the temperature dependence of binding kinetics and thermodynamics (e.g., melt/denaturation profile) in a single experiment.

Influence of attachment strategy on the thermal stability of hybridized DNA on gold surfaces.

The thermal stabilities of double-stranded DNA hybrids immobilized on gold surfaces are shown to be significantly affected by the conformation of the hybrid. To analyze this behavior, DNA probes were immobilized using attachment strategies where the nucleotides within the strand had varying levels of interactions with the gold substrate. The abilities of these probes to form double-stranded hybrids with solution DNA targets were evaluated by surface plasmon resonance (SPR) over a temperature range 25-60 °C. The measurements were used to construct thermal stability profiles for hybrids in each conformation. We observe that DNA hybrids formed with probe strands that interact extensively with the gold surface have stability profiles that are shifted lower by 5-10 °C compared to hybrids formed with end-tethered probes that have fewer interactions with the surface. The results provide an understanding of the experimental conditions in which these weaker DNA hybrids can form and show the additional complexity of evaluating denaturation profiles generated from DNA on surfaces.