In this study, the physicochemical and functional properties of Idesia polycarpa whole fruit protein (IPWP), Idesia polycarpa pericarp protein (IPPP), and Idesia polycarpa seed protein (IPSP) were compared. To reveal the differences in the properties of Idesia polycarpa proteins in different extraction sites, it was also compared with commercially available soybean protein isolate (SPI) to explore the potential of Idesia polycarpa protein application. It was found that the protein content (69.13%±0.61%) and total amino acid content of IPSP were significantly higher than those of IPWP and IPPP (P<0.05). The three Idesia polycarpa proteins all exhibited a porous structure, with molecular weights below 45 kDa, among which IPSP had the most extended structure and the highest content of the 18.4 kDa subunit. At the same pH, IPWP and IPSP showed smaller average particle size and higher absolute value of Zeta-potential and surface hydrophobicity than IPPP. The three Idesia polycarpa proteins demonstrated superior solubility, foaming capacity, and emulsifying activity compared to SPI. Compared with IPWP and IPPP, IPSP possessed enhanced solubility, foam stability, emulsification and emulsion stability, especially at pH7, the solubility and emulsion stability of IPSP increased by 79.47% and 43.65%, respectively, than those of IPPP. In summary, the performance of the three Idesia polycarpa proteins was better than that of the commercially available SPI. IPSP showed the greater advantages in protein composition and functional properties. This study would provide the basic theoretical and technical support for the high-value utilization and development of Idesia polycarpa functional components.

This study aimed to investigate the enzymatic hydrolysis effects of papain, alkaline protease, neutral protease, alkaline protease TG enzyme combination, and papain alkaline protease combination on gluten protein and their impact on its structure. The degree of hydrolysis, trichloroacetic acid nitrogen solubility index (TCA-NSI), and molecular weight distribution were used as evaluation indicators to the enzymatic hydrolysis. The surface hydrophobicity, free thiol groups, and protein microstructure were determined using Fourier transform infrared spectroscopy, intrinsic fluorescence spectroscopy, UV spectroscopy, and other methods, and the structural changes of enzymatic hydrolysis products were systematically characterized. The results showed that enzymatic hydrolysis significantly increased the degree of hydrolysis of wheat gluten protein. The increase in surface hydrophobicity and free thiol content indicated significant changes in the protein's tertiary structure. Secondary structure analysis showed that in wheat gluten protein, the β-folding structure was transformed into irregular curls. The comparison of molecular weight distribution before and after enzymatic hydrolysis showed that the papain alkaline protease combination could more effectively hydrolyze wheat soluble protein. In addition, changes in the microstructure indicated that enzymatic hydrolysis altered the conformation of protein molecules. Therefore, this study provides theoretical support for the study of structural changes in wheat gluten after protein hydrolysis, and provides scientific basis for the development of high solubility and high functionality gluten protein products.

The industrial production of steamed stuffed bun frequently encounters challenges such as dry wrapper and foaming after steaming. To further investigate the influence of the steaming process on the structural characteristics of steamed stuffed bun, this study utilized flour with protein contents of 8%, 10%, and 12% as raw materials. A combination of experimental techniques, including texture analysis, low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM), was employed to analyze the structural characteristics, water distribution, secondary structure, tertiary structure, and microstructure of steamed stuffed bun wrapper at various steaming time points. The results demonstrated that the specific volume, elasticity, and resilience of the steamed stuffed bun wrapper increased with both the extension of steaming time and the increase in protein content. Additionally, the levels of bound water and free water rose, enhancing water fluidity. With the rise in disulfide bond content, the disulfide bonds transitioned from t-g-t and g-g-t structures to g-g-g structures. When the protein content of the steamed stuffed bun wrapper reached 12%, the β-sheet and β-turn structures increased by 4.58% and 8.36%, respectively, as steaming time progressed. At a steaming time of 16 minutes, the β-sheet and β-turn structures increased by 0.31% and 5.06%, respectively, with increasing protein content. The tertiary structure of gluten proteins became more compact as steaming time increased. Simultaneously, non-covalent interactions contributed to the formation of a starch-protein network, with non-covalent bonding forces strengthening as steaming time extended. The crystallinity of starch particles decreased, along with a reduction in the intensity of diffraction peaks. As cooking time increased, starch particles diminished in size and became increasingly embedded within the damaged gluten matrix, forming a starch-gluten protein network system. Furthermore, higher gluten proteins content resulted in tighter integration between starch particles and gluten proteins. These findings provide a theoretical basis for addressing issues related to the hardness and foaming of steamed stuffed bun and offer data support for optimizing process parameters and industrial production.

During the storage and sale of bottled huangjiu, precipitation caused by non-biological factors frequently compromises consumer acceptance. Ultrafiltration has been widely used to control huangjiu's non-biological stability, but this treatment's impact on the storage stability and flavor of huangjiu is unclear. In this study, bottled huangjiu was treated with ultrafiltration membranes featuring pore sizes of 50, 30, 10, 5, and 3 kDa, monitoring colloidal stability parameters (turbidity, polyphenol turbidity, centrifugal sedimentation rate, particle size, and Zeta potential) after 1, 150, and 270 days of storage. The precipitable components, antioxidant properties, physicochemical indices, and volatile and non-volatile substances of huangjiu in the later storage period (270 days) were determined, the sensory and color changes of huangjiu were evaluated, and the optimal pore size of ultrafiltration membrane was determined. Results demonstrated that ultrafiltration notably diminished turbidity, polyphenol-related turbidity, and centrifugal sedimentation rates in the huangjiu, significantly enhancing its storage stability. Both the 50 kDa membrane and smaller pore sizes yielded optimal treatment outcomes. Colloidal property assessments suggested that ultrafiltration might have eliminated large molecular proteins, resulting in a reduced mean particle size of the huangjiu colloid, a more uniform particle size distribution, and an elevated Zeta potential. Over the storage period, the 50 kDa ultrafiltration membrane more effectively preserved the flavor and color of the huangjiu, whereas membranes with 30 kDa and smaller pore sizes caused varying degrees of flavor weakening and color lightening. The retention of antioxidant activity, volatile compounds, and non-volatile constituents decreased with smaller membrane pore sizes. The 50 kDa membrane had the least impact on functional components, volatile compounds, and non-volatile constituents. This study elucidated the comprehensive effects of ultrafiltration on storage stability, precipitable components, functional constituents, and sensory properties in bottled huangjiu. Considering stability enhancement, flavor preservation, and sensory acceptance, the 50 kDa ultrafiltration membrane showed the best application potential in solving the precipitation problem in huangjiu processing, providing scientific guidance for quality optimization.

Gluten is an important component that controls the quality of dough and flour in food. To improve the quality of potato gluten-free food by replacing gluten with protein gel, the functional properties of potato-rice protein composite gels with different ratios and the effects of appropriate addition amounts on the hydration and rheological properties of dough made from gluten-free potato flour were studied. The results showed that, compared with pure potato protein gel, the pore size of the composite gel network with a compounding ratio of 1:0.5 was reduced, network structure was denser and more uniform, water retention increased by 36.6%, emulsion stability increased by 31.7%, and gel strength and Zeta potential were higher. The optimal ratio of 0%~8% composite gel was added to potato powder. With an increase in the amount of composite gel, the relaxation time (T₂), bound water (A₂₁), and immobile water (A₂₂) of the dough first increased and then decreased, free water (A₂₃) decreased, and water mobility in the dough decreased. The storage modulus (G') and loss modulus (G'') of the dough as well as the loss tangent value (tanδ) continued to increase. The stress relaxation characteristics (E₀ and E₁ values) and the hardness of the dough first decreased and then increased, whereas the elasticity, cohesion, adhesiveness, resilience, and viscoelasticity of the dough increased. These results confirmed that the potato-rice protein composite gel exhibited good functional properties, and the addition of 4% composite gel effectively compensated for the deficiency of potato gluten-free protein and further improved the processing quality of the dough.

To enhance the stability of emulsions prepared with soybean protein isolate (SPI) as the sole emulsifier, this study developed composite sunflower seed oil emulsions (SPI-XG-e) and bilayer emulsions (SPI-e/XG) using SPI and xanthan gum (XG) as co-emulsifiers. The primary objective was to investigate the effects of XG concentration on the physical characteristics of the emulsions, including mean particle size, Zeta potential, and turbidity, as well as their overall stability. The findings revealed that at a XG concentration of 1.0%, the bilayer emulsion demonstrated superior physical properties, characterized by a more uniform particle size distribution, a smaller mean particle diameter (0.63±0.03 μm), a higher absolute Zeta-potential value (46.70±0.25 mV), and a lower centrifugal stability constant (0.70%±0.46%). Comparative analysis of the composite and bilayer emulsions revealed that the latter exhibited enhanced environmental stress tolerance. Particularly, the bilayer emulsion prepared with 1.0% XG could maintain homogeneity for 7 days of storage at 4 ℃ with no detectable phase separation. After thermal treatment at 90 ℃, it retained a high absolute Zeta-potential value (44.47±0.31 mV) and showed no flocculation following three freeze-thaw cycles, demonstrating robust stability. This study provides actionable guidelines for developing highly stable oil-in-water emulsions in food manufacturing processes.

In order to explore the effects of different sourdough flavor starters on the quality of steamed bread, angel yeast steamed bread (AQ), Kazachstania humilis-Lactobacillus plantarum-Weissella cibaria fermented steamed bread (FP), Kazachstania humilis fermented steamed bread (JM), Kazachstania humilis-Lactobacillus plantarum fermented steamed bread (JZ), Kazachstania humilis-Weissella cibaria fermented steamed bread (JS) and industrial sourdough steamed bread (LM) were analyzed and compared for the pH value, titratable acidity (TTA), dough fermentation power, specific volume, color difference, texture, electronic nose sensing value and sensory evaluation. The results showed that compared with LM group, pH of the experimental steamed bread was lower (5.47~5.67), the pH of steamed bread in the FP group significantly decreased by 13.6% (P<0.05), TTA was higher (10.38~11.80 mL). The hardness and chewability of experimental groups was lower than that in the LM group (P<0.05), and the hardness and chewability of FP were moderate and the elasticity was best when Kazachstania humilis, Lactobacillus plantarum and Weissella cibaria were added at the same time. The L^* values of FP steamed bread and AQ steamed bread were significantly higher than those of LM group (P<0.05), and the luster was good. The results of electronic nose experiment showed that the three kinds of sourdough flavor starters had a great influence on the formation of flavor substances, including alkane and ethanol in steamed bread, among which FP and LM showed almost identical positions in radar map, proving that they had a high degree of consistency in flavor. In addition, the correlation analysis results between the addition of strains and the quality of steamed bread showed that Lactobacillus plantarum could significantly (P<0.05) reduce the pH value of steamed bread, Kazachstania humilis could not only significantly (P<0.01) reduce the pH value but also regulate the specific volume of steamed bread, and Weissella cibaria could significantly (P<0.05) affect the color and textural property of steamed bread. Therefore, we can get good quality, good chewing, white and shiny steamed bread through the combination of three kinds of sourdough flavor starters. The experimental results can provide theoretical support for the standardized production of sourdough flavor starters.

To prepare a probiotic fermented milk that could produce antibacterial substances in situ, Limosilactobacillus reuteri HLRE05, which had the ability to metabolize glycerol into broad-spectrum antimicrobial Reuterin, was used to investigate the optimum conditions for preparation of the fermented milk. This study aimed to evaluate the effects of glycerol addition on the Reuterin production and the properties of the fermented milk, analyze the biochemical indices and the Reuterin content of the fermented milk during storage, and assess antibacterial ability. The results showed that the optimal preparation conditions for the Reuterin-containing fermented milk was a total inoculum volume of 5%, with a 1:1 ratio of YO-MIX 495 to HLRE05, a sugar content of 6% (a 1:1 ratio of rhamnose to sucrose), and a fermentation temperature of 37 ℃. When supplemented with glycerol at a concentration of 100 mmol/L, the in situ production of Reuterin reached 0.28 mg/mL, and the content of L. reuteri and water retention in fermented milk were better. In addition, fermented milk contained Reuterin maintained good water-holding capacity, stable pH and high Reuterin concentration, and was characterized by the effective inhibition of pathogen proliferation during storage. This study could pave the way for the exploration and application of characteristic lactic acid bacteria, such as L. reuteri HLRE05, in dairy products.

In this study, the effects of adding anthocyanins (0.45~2.70 g/100 g rice flour) extracted from Lycium ruthenicum Murr on the quality improvement of steamed rice bread were investigated through textural profile, gas cell distribution, and sensory evaluation. The mechanisms underlying the effects of anthocyanins on the starch gel network and fermentation of steamed rice bread were investigated based on rheology and Fourier transform infrared spectroscopy (FTIR). The results revealed that the optimal amount of supplementary anthocyanin extract was 1.80 g/100 g rice flour, which gave rise to steamed rice bread with a hardness of 14.02 N, a specific volume of 1.78 mL/g, and a sensory evaluation score of 76.63. The red shift of the -OH stretching vibration peak in the FTIR spectrum indicated that anthocyanin extracts might bind to starch molecules through hydrogen bonds. The increase of R_1052/1022 in the deconvolution curve suggested that the addition of anthocyanin extracts increased the short-range order of starch. The rheological results showed that anthocyanin extracts decreased the complex modulus (|G^*|) of rice paste and promoted the expansion of gas cell chambers in the steamed rice bread. In addition, anthocyanins acted as an indicator for the fermentation process based on their pH-dependent color, giving a bright color and good appetite to the steamed rice bread. In conclusion, the addition of anthocyanin extracts from Lycium ruthenicum Murr could promote the gelation and fermentation of steamed rice bread by regulating the starch gel network, resulting in quality improvement.

To investigate the differences in the quality characteristics of pigeon meat under various cooking methods, a comparative study was conducted to analyze the impacts of five commonly used cooking methods, namely boiling, steaming, pan-frying, deep-frying, and roasting, on the structural changes, oxidation, and digestive properties of pigeon meat protein. The results showed that, steaming had the least impact on protein structure and oxidative properties of pigeon meat, while roasting had the most significant effect, with boiling, pan-frying, and deep-frying falling in between. Compared to the control group, β-sheet relative content increased from 24.04% to between 30.05% to 39.71%, while α-helix relative content decreased from 27.26% to between 15.29% and 20.66% under various cooking methods. The carbonyl content increased from 1.36 nmol/mg to 3.04~7.90 nmol/mg, and total sulfhydryl content decreased from 76.25 μmol/g to 50.78~61.40 μmol/g. All the cooking methods increased the protein digestibility (3.10%~11.31%). In particular, steaming exhibited the smallest increase in surface hydrophobicity (49.56 μg) and the smallest decrease in α-helix relative content (24.21%). Furthermore, the steaming resulted in the lowest oxidation levels, with carbonyl content increasing by only 1.68 nmol/mg, a 19.47% reduction in total sulfhydryl content, and the lowest degree of aggregation. After simulated gastrointestinal digestion, steaming exhibited the highest protein digestibility (67.43%), surpassing the roasted group by 4.99%, with the digested product demonstrating the smallest particle size. Correlation analysis indicated that carbonyl content was positively correlated with β-sheet relative content (P<0.01), total sulfhydryl content was positively correlated with α-helix relative content (P<0.001), and negatively correlated with both surface hydrophobicity and β-sheet relative content (P<0.05). Protein oxidation was significantly related to protein structural changes and synergistically regulated digestive properties. In summary, steaming is the best cooking method to improve the quality characteristics of pigeon meat. This study provides the theoretical basis for the regulatory mechanisms of protein structure and function of pigeon meat and the optimization of cooking technology.