Food Biophysics最新文献

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.

Phlorotannins (PHT) are phenolic substances found in marine brown seaweeds that have a lot of different biological effects. However, their poor stability restricted their usage in different fields. Here, we encapsulated PHT using a freeze-drying technique. Process parameters, including wall material type (maltodextrin, whey protein, and their combination), wall concentration (0.03–0.1 w/v), and core-to-wall ratio (2–5), were optimized using the response surface method with a central composite design (CCD) to attain the best capsule. The optimum encapsulation with the highest PHT efficiency (85.67%) and antioxidant activity (67.34%) was produced with a whey protein/maltodextrin blend encapsulating at 0.03 w/v and 5 PHT-to-wall ratios. Findings from SEM studies on optimal capsules revealed that the particles are irregular in shape, with some pores on the surface. Furthermore, the FTIR study validated the encapsulation of PHT, and the TGA data suggested that encapsulation enhanced the thermal stability of PHT. Further, encapsulated PHT (En-PHT) was added to pasteurized milk to increase its shelf life. The findings indicate that the addition of En-PHT restricts microbiological proliferation, prolonging milk’s shelf life from 4 days to 8 days while maintaining acceptable sensory attributes. This study suggests that En-PHT could be exploited as an ingredient to produce new, functional milk.

This research prepared an antibacterial active packaging material based on carboxymethyl chitosan/polyvinyl alcohol (CMCS/PVA) loaded with cerium dioxide nanoparticles (CeNPs), and evaluated its potential application in fruit preservation. The results of Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) indicated that CeNPs were uniformly dispersed in the film matrix, and the components of the film exhibited good compatibility. The composite films containing CeNPs also exhibited excellent mechanical properties. Compared with the CMCS/PVA (CP) film, their tensile strength increased from 15.22 MPa to 30.72 MPa, and the elongation at break rose from 43.17% to 101.79%. Meanwhile, the incorporation of CeNPs enhanced the barrier properties of the composite films. The composite film with 5% CeNPs exhibited excellent ultraviolet shielding ability, with a transmittance of nearly 0% in the range of 200–315 nm, and possessed outstanding gas barrier performance, with the water vapor permeability (WVP) decreased by 35%. In addition, the CP-CeNPs composite film exhibited stronger DPPH and ABTS radical scavenging activities (50.55%, 77.12%), with inhibition rates against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) reaching 99.66% and 96.80%, respectively. The composite film showed no toxicity to RAW 264.7 mouse macrophages, with a cell viability of over 80%. Finally, it extended the shelf life of strawberries by 7 d at 25 °C. The findings demonstrated that the composite film provided a novel approach for preparing active packaging materials and showed promising potential in fruit preservation packaging applications.

Graphical Abstract

Both lutein and chlorophyllin are vital natural pigments. However, the application of lutein has been limited due to its low environmental stability and poor bioavailability. Herein, lutein/Cu-Chlorophyllin (L-Chls) composites have been fabricated via a simple and mild solvent-mixing process at room temperature. Compared to the pristine lutein, the synthesized L-Chls showed 5.2 times higher photostability and 6.9 times better antioxidant ability. The retention rate and thermostability in the air also improved by 77% and 23%, respectively. The experimental results reveal the energy/electron co-transfer at the interface of lutein and Cu-Chl, and a possible mechanism for the enhanced photostability and antioxidant ability of the L-Chls has been proposed. This work provided a feasible strategy to improve the stability and antioxidant ability of lutein, and can also be expanded to the functional food and pharmaceutical field.

In this study, we investigated the physicochemical and rheological properties of xanthan gum (XG) in milk protein isolate (MPI)-based aqueous and emulsion systems at varying MPI concentrations (0–2.0%). MPI-based aqueous systems exhibited relatively higher ζ-potential values (-12.1 to -14.1 mV) than emulsion systems (-21.2 to -27.8 mV), suggesting a conformational transition of MPI during emulsification. The ζ-potential of the emulsion system decreased with increasing MPI concentration, leading to enhanced stability. The addition of XG further improved stability by forming a dense viscoelastic 3D network that restricted particle mobility. The intrinsic viscosity of XG in both systems decreased with increasing MPI concentration, indicating the formation of a more compact conformation due to electrostatic repulsion with MPI or emulsion particles. Consequently, the apparent viscosity and viscoelastic moduli values for XG increased, reflecting stronger intermolecular interactions among closely packed molecular chains. Notably, a more pronounced increase was observed in the emulsion system. The enhanced rheological properties are likely attributable to the formation of more negatively charged particles upon emulsification, which promoted XG molecule contraction in the emulsion system. This conformational transition facilitated interactions between negatively charged XG and positively charged peptide domains protruding on the emulsion particle surfaces. These findings highlight that emulsification alters MPI conformation, thereby changing its interaction with XG and leading to distinct rheological behaviors of XG in aqueous and emulsion systems. With this in mind, the design of gum-based thickeners for dysphagia should account for beverages containing emulsified phases to achieve optimal texture, stability, and swallowing safety.

Lycopene extract from tomato peel by-products was encapsulated in oil-in-water (o/w) nanoemulsions of a combination of b-cyclodextrin and dextran prepared by ultrasonic emulsification. The stability of the nanoemulsions was assessed through analytical photocentrifugation, followed by spray drying to produce nanoencapsulated powders. The characterization of the lycopene nanoparticles included assessment of encapsulation efficiency, antioxidant activity, and physicochemical and structural properties. Extending the ultrasonic emulsification process to 16 min resulted in the production of nanoemulsions with satisfactory physical stability, achieving a higher encapsulation efficiency of 96.17%, and improved solubility with a percentage dispersion in aqueous media of 97%. The powders produced, with a water content and water activity of 2.3% and 0.33, respectively, confirmed the effectiveness of the spray drying process. Microscopically observed particles showed a spherical nanoscale morphology with an average diameter of 100.87 ± 1.23 nm. This finding indicated that ultrasonic treatment of the emulsions led to a substantial reduction in particle size. The zeta potential of the nanoparticles, recorded at -20.09 mV, indicated that the particles exhibited a moderate stability. This observation was corroborated by the results of storage for 30 days at different temperatures in dark or light conditions. The lycopene nanoparticles produced demonstrated acceptable stability, with lycopene degradation levels of 9%, 14%, 21%, and 26% at 4 °C and 25 °C in light and at 30 °C and 40 °C in the dark, respectively. This study demonstrates that nanoencapsulation by ultrasonic emulsification is a promising method for producing lycopene nanoparticles with high solubility and potential for food applications.

In this study, we investigated the development of gum Arabic (GA)-based composite coatings functionalized with keratin (K) and cinnamon oil (CO) to enhance the physicochemical, nutritional, and microbial stability of tomatoes. Coating formulations containing GA-K-CO_0.1 (27:3:0.1, v/v/v) and GA-K-CO_0.5 (27:3:0.5, v/v/v) were developed and applied as coatings. Mature green tomatoes were treated with GA-K-CO_0.1 and GA-K-CO_0.5 and stored at 27.5 °C and 80.7% relative humidity (RH) for 20 days, with quality assessments at 5-day intervals. Formulations with a GA-K-CO_0.1 concentration extended the shelf life of tomatoes by up to 5 days under ambient conditions. This was achieved by significantly reducing weight loss by 31.9%, decay incidence by 33.3%, and exhibiting significant antifungal activity (p < 0.05) compared with the uncoated control, which was coated with distilled water. The tomatoes coated with GA-K-CO_0.5 showed about a 6.21% retention in moisture content, total soluble solids, and a rise of roughly 60% in antioxidant capacity compared with control group. The formulation with a lower level of cinnamon oil in GA-K-CO_0.1 showed a significant (p < 0.05) retention in β-carotene and lycopene levels, and further enhanced nutritional and visual quality, as well as its potential to inhibit bacterial and fungal growth. The gum Arabic-based coating functionalized with keratin and cinnamon oil presents a novel and sustainable method for postharvest tomato preservation, holding considerable promise to lower losses and improve food quality in supply chains.