Food Biophysics最新文献

The stability of digestive enzymes in macromolecular environments is critical for their performance during food processing, storage, and digestion. Here, the unfolding of porcine pancreatic lipase (PPL) in urea solutions supplemented with polyethylene glycol (PEG), dextran, Ficoll, or Pluronic were examined. By integrating fluorescence spectroscopy with stopped-flow kinetics, the unfolding progression were monitored and a quantitative model to elucidate the underlying mechanisms was developed. The results show that the unfolding pathway of PPL varies with the macromolecular medium, adopting two-, three-, or four-state models in Pluronic, PEG/dextran, and Ficoll 70, respectively, demonstrating that macromolecular crowding directs conformational transitions. A denaturant-binding model parameterized by τ (transition equilibrium constant) and m (cooperativity index) was established to quantitatively describe these processes. Together, this work offers mechanistic insight into how macromolecular surroundings shape the structural dynamics and function of digestive enzymes.

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Polysaccharide-based polymeric films have gained prominence as sustainable systems for functional applications, especially when incorporated with bioactive compounds such as eugenol. In this study, alginate, carrageenan, and chitosan films with different concentrations of eugenol were developed to evaluate the effects on their physicochemical, structural, and functional properties. The films were characterized for thickness, solubility, mechanical properties, water vapor permeability, contact angle, as well as FTIR, X-ray, TGA, and SEM analyses. The results showed that the incorporation of eugenol increased film thickness, particularly in formulations alginato 50% (ALG-50) (0.103 mm) and carrageena 50% (CAR-50) (0.107 mm). Solubility was complete in alginate and carrageenan films, while chitosan films exhibited greater water resistance. Chitosan (CS) provided higher mechanical strength in Chitosan 35% (CS-35) (64.75 MPa), whereas alginate and carrageenan offered greater elongation. Permeability and contact angle were influenced by both the type of polysaccharide and the eugenol load, with chitosan films showing greater hydrophobicity. Structural analyses revealed specific chemical interactions between eugenol and each polymer matrix, affecting crystallinity and thermal stability. Film morphology varied according to formulation, highlighting the influence of eugenol on surface compactness and uniformity. It is concluded that film property modulation strongly depends on the type of polysaccharide and eugenol concentration, indicating their potential for use in active systems such as functional packaging and controlled release of bioactive compounds.

Thickened fluids minimize the risk of dehydration, choking, and aspiration in individuals with dysphagia. Although shear and extensional properties are critical to fluid behavior during swallowing, comprehensive rheological data remain limited. This study aimed to evaluate the shear and extensional rheology of fluids thickened with xanthan gum (XG), guar gum (GG), and gellan gum (GeG) using Capillary Breakup Extensional Rheometry with the Dripping-onto-Substrate (CaBER-DoS) method. Aqueous solutions with gum concentrations corresponding to International Dysphagia Diet Standardisation Initiative (IDDSI) levels 1 to 4 were prepared and characterized for their microstructure and physical stability. Shear rheology revealed that XG and GeG solutions exhibited pronounced shear-thinning and linear elastic behavior (G′ >G″), while GG achieved the highest viscosity through coil entanglements. Extensional viscosity and filament breakup time increased with IDDSI levels, with GG > XG ≈ GeG. Microstructural analysis showed large aggregates in GG solutions, whereas XG and GeG formed finer, more uniform networks. Zeta potential measurements indicated that XG and GeG possess highly negative surface charges, enhancing colloidal stability and preventing aggregation, in contrast to the aggregation-prone GG. The interplay between surface tension, zeta potential, and microstructure formation has significant implications for bolus cohesiveness and oral processing behavior. While surface tension reductions may aid film formation and stability, it is the combined effect of molecular architecture and network dynamics that ultimately governs the functionality of gum-thickened liquids in dysphagia management. These findings offer mechanistic insights for designing texture-modified fluids that ensure safe swallowing and optimal sensory properties.

Dried sourdough enables stable storage, easier transport, and simplified mixing. In addition to widely studied drying techniques and conditions, assessing the moisture absorption behaviour of sourdough powder is essential for optimizing drying, storage, and packaging conditions. Herein, it was aimed to investigate the effects of vacuum-drying on the morphology, chemical structure, and moisture adsorption behaviour of sourdough (VDSP) by comparing commercially available sourdough powder (CSP). The CSP sample exhibited a heterogeneous distribution of relatively larger particles, whereas the VDSP sample exhibited a more fragmented morphology with smaller particles, indicating that the fundamental microstructure remained largely unaltered. FTIR spectra showed a slight decrease in the 3300 cm⁻¹ band intensity for the VDSP, which reflected reduced hydrogen bonding capacity. Accordingly, the moisture content of the CSP sample reached 2-fold that of the VDSP beyond 0.60 water activity. Both samples followed Type II isotherms and moisture adsorption required external energy (ΔG > 0). Sorption modelling indicated that the Smith and Caurie models effectively described the VDSP moisture adsorption behaviour. Overall, vacuum-drying emerged as a promising alternative drying method for sourdough powder production, providing enhanced stability and reduced moisture adsorption, particularly at high relative humidity, while preserving key chemical structural properties. These findings suggest that it has strong potential for industrial applications compared to relatively more expensive and complex methods such as freeze-drying and spray-drying.

Soybean is one of the most common sources of plant protein used in plant-based meat alternatives, but the bean flavor in final product limits its wide application. Lipophilic proteins (LPs) constitute approximately 31% of soy protein isolate and contain 11–13% lipids. Therefore, it is hypothesized that the oxidation of protein and lipids in LPs may significantly influence the bean flavor formation. The volatility components of LPs were examined under various heating conditions. The effects of curcumin and tea polyphenols on the bean flavor components were also investigated. The present study further explored the role of lipid oxidation and protein modification in LPs in the bean flavor formation through changes in malondialdehyde content, fatty acid composition and protein structure. The total content of 22 types of bean flavor, including nonanal, benzaldehyde, hexanal, and others, rose from 22.72 µg/L to 67.70 µg/L as the temperature increased from 120 to 180 °C. In the LPs samples with curcumin and tea polyphenols, the total content of bean flavors decreased to 48.54 µg/L and 29.04 µg/L at 180 °C, respectively. The protective effects of curcumin and tea polyphenols on unsaturated fatty acids C18:1, C18:2, and C18:3n3 exhibited variation. Antioxidants didn’t exhibit superiority in protecting against overall lipid oxidation according to measurement of malondialdehyde. Ultraviolet and fluorescence spectra showed that tea polyphenols had a stronger interaction with LPs in protein structure. In summary, the incorporation of tea polyphenols emerges as a promising approach to impede bean flavor formation for plant meat production.

This research primarily investigates the encapsulation of curcumin within curdlan-whey protein isolate(CUR-WPI) composite gels and the subsequent release of the encapsulated compound. Results demonstrated that the composite gel could effectively encapsulate curcumin, with the highest encapsulation rate reaching 83.6%. The main force for the gel to encapsulate curcumin was electrostatic interaction and hydrogen bond. Fluorescence spectroscopy showed that curcumin can bind to WPI through hydrophobic interactions and suppress WPI's natural fluorescence. The composite gel exhibits excellent water-holding capacity (WHC) and the favorable texture profile analysis (TPA), which improved the photostability (2.57 times) and storage stability of curcumin (6.09 times). Moreover, the release rate of curcumin from the composite gel in intestinal fluid was higher than that in the stomach, which was related to the non-digestible characteristics of the curdlan and the dense network structure of the gel. The release kinetics results indicated that the main release mechanism of curcumin in the composite gel during the simulated digestion process was the diffusion mechanism. In conclusion, CUR-WPI composite gel is a good delivery carrier for curcumin, indicating its potential value for application in functional dairy products.

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Protein stability depends on both subunit folding and inter-subunit interactions, which are modulated by environmental conditions and cosolutes. This study examined how polyethylene glycols (PEG) of different molecular weights affect the structural stability of the multimeric protein C-phycocyanin (CPC). Using differential scanning calorimetry (DSC), fluorescence spectroscopy, and rheology, we analyzed CPC in the presence of PEG 4 000 g/mol (PEG4) and PEG 35 000 g/mol (PEG35). Fluorescence spectroscopy showed that both PEGs increased the emission intensity of CPC without shifting the emission maximum, indicating changes without major alterations of the global structure. DSC revealed a marked decrease in the enthalpy of unfolding, particularly with PEG35, despite only slight changes in denaturation temperatures. Rheology demonstrated effects of CPC on PEG solution viscosity. These results suggest that the smaller size and lower hydration of PEG4 allow it to intimately penetrate the hydration shell of CPC. In contrast, the larger molecular weight and higher hydration number of PEG35 induce protein-protein association and loss of solubility. Altogether, these results show that PEG molecular weight governs CPC stability: PEG4 may destabilize CPC via crowding and hydration-shell disruption, whereas PEG35 is likely to reduce CPC solubility through depletion-driven aggregation without altering its folded structure.

Dihydrocaffeic acid (DHCA) is a phenolic compound known for its antioxidant properties but suffers from limitations due to its hydrophilicity. This study focused on enzymatically synthesizing DHCA esters with alkyl chains ranging from C4 to C12 to enhance their lipid compatibility, while also assessing their safety and effectiveness. The esters were produced using Candida antarctica lipase B, yielding between 37.40 ± 4.41% and 59.34 ± 0.31%. Antioxidant assays, including DPPH, ABTS, CUPRAC, and lipid systems, indicated that the antioxidant activity was dependent on chain length: shorter esters excelled in polar assays (e.g., C4-DHC IC₅₀ = 0.14 ± 0.01 mM in DPPH), whereas longer chains (C8-DHC and C12-DHC) were more effective in lipid-rich environments. In vegetable oils, both DHCA and its esters significantly reduced oxidation, similarly to butylated hydroxytoluene (BHT), under both storage and accelerated conditions. Cytotoxicity tests performed on HaCaT cells showed that short-chain esters (C4-DHC and C8-DHC) were toxic at concentrations of 0.1 mM and above, while C12-DHC maintained 61.6 ± 15.0% viability at 0.1 mM. Phytotoxicity effects varied by species, with C12-DHC exhibiting minimal inhibition of germination. The results highlighted the critical role of alkyl chain length in influencing antioxidant effectiveness and safety. Longer esters, specifically those with chain lengths of C8–C12, provided a favorable balance of lipid solubility, oxidative stability, and biocompatibility, making them sustainable options for food additives. Further in vivo studies are also needed to verify their safety in cosmetics and agriculture.

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Drying is a critical step in the processing of Chinese herbal medicines; however, this process can induce quality deterioration in rhubarb, leading to the loss of bioactive components and visual degradation. To address this, the present study focuses on vacuum freeze-drying (VFD) technology and investigates the influence of slice thickness (2–8 mm) on drying kinetics, color, enzyme activity, and bioactive constituents, with the aim of optimizing the VFD process parameters. The results showed that the enzymatic browning was not significant during the whole drying stage (0–18 h), the catalase activity increased first and then decreased, and the polyphenol oxidase activity showed a stable trend, which was synchronized with the peak browning. The 6 mm slice retained the highest anthraquinone content, while the thinner slice (2 mm) showed the greatest loss. Moisture reduction follows a logarithmic model with high accuracy (R² = 0.995). Metabolomic analysis identified 617 differential metabolites, including 6 key compounds related to the biosynthesis of flavonoids and other compounds, which were regulated by 9 enzymes. By constructing a mathematical model of drying dynamics, Page model fitting effect was the best. Therefore, optimizing the slice thickness (6 mm) and controlling the early drying (< 18 h) effectively improved the product quality and provided insights for the cold drying of other medicinal plants.

Flaxseed meal, a by-product of flaxseed oil processing, is rich in flaxseed gum (FSG) but often wasted due to low-value use. This study aimed for its high-value transformation via process optimization. First, the ultrasonic-assisted extraction of FSG was optimized. Single-factor and Box-Behnken response-surface methods determined the optimal extraction: liquid-to-solid ratio 50 mL/g, pH 6, ultrasonic power 249 W, time 42 min, with a 27.12% extraction rate. It was innovatively proposed and verified that acidic conditions favor the Maillard reaction of FSG and soybean protein isolate (SPI). Single-factor and response-surface optimization set the optimal modification at pH 4.8, 84 °C, 104 min, preparing FSG-SPI conjugates with a 61.74% grafting degree. Structural analysis confirmed covalent binding, and SEM showed a dense flake-like structure. Functional analysis indicated improved properties compared to FSG (P < 0.05). This study offers a high-value utilization strategy for flaxseed meal and reveals the advantages of acidic Maillard modification, laying a foundation for new food ingredients.