Characterization of structural and functional properties of soybean 11S globulin during renaturation after denaturation induced by changes in pH.

BACKGROUND: This study explored the denaturation of 11S globulin, a protein known for its diverse functional properties in soy protein applications, at pH 3.0 and pH 10.0, followed by a gradual return to pH 7.0 to facilitate renaturation. It investigated the structural and functional changes during renaturation induced by a change in pH, revealing the stabilization mechanism of 11S globulin. RESULTS: The findings revealed that during pH adjustment to neutral, the denatured soybean 11S globulin - resulting from alkaline (pH 10.0) or acidic (pH 3.0) treatments - experienced a refolding of its extended tertiary structure to varying extents. The particle size and the proportions of α-helix and ß-sheet in the secondary structure aligned progressively with those of the natural-state protein. However, for the alkali-denatured 11S, the ß-sheet content decreased upon adjustment to neutral, whereas an increase was observed for the acid-denatured 11S. In terms of functional properties, after alkaline denaturation, the foaming capacity (FC) and emulsifying activity index (EAI) of 11S increased by 1.4 and 1.2 times, respectively, in comparison with its native state. The solubility, foamability, and emulsifiability of the alkali-denatured 11S gradually diminished during renaturation but remained superior to those of the native state. Conversely, these properties showed an initial decline, followed by an increase during renaturation triggered by pH neutralization. CONCLUSIONS: This research contributes to the enhancement of protein functionality, offering a theoretical foundation for the development of functional soy protein products and expanding their potential applications. © 2024 Society of Chemical Industry.

Effects of soybean isoflavone aglycone on osteoporosis in ovariectomized rats.

Postmenopausal osteoporosis is one of the most common metabolic diseases in old women, and supplementing estrogen through bioactive substances is one of the important ways to improve menopausal syndrome. Some studies have confirmed that soybean isoflavone has estrogenic activity, and the main active component of soybean isoflavones is isoflavone aglycones. However, few studies have investigated the improvement effect of high-purity soy isoflavone aglycones on postmenopausal osteoporosis. Thus, the effect of different doses of high-purity soybeans isoflavone aglycone on the ovariectomized female osteoporosis rat model was evaluated by oral gavage. The rats were divided into seven experimental groups including SHAM, OVX, EE, SIHP, AFDP-L, AFDP-M, and AFDP-H, which was administered for 60 days from 30 days after ovariectomy. We collected blood from the abdominal aorta of rats on the 30th, 60th, and 90th days respectively, analyzed its serum biochemistry, and took out the femur for micro-CT imaging and bone microstructure parameter analysis. Results showed that the intervention effect of AFDP-H group on osteoporosis rats at 60 and 90 days was similar to that of EE group, and superior to the OVX group, SIHP group, AFDP-L group, AFDP-M group. The AFDP-H group inhibited the decrease in serum bone markers, bone density, trabeculae quantity, trabeculae thickness, and bone volume fraction, and increased the trabecular separation caused by ovariectomy, thereby significantly improving bone microstructure. It also prevented continuous weight gain and increased cholesterol levels in female rats. This study provided theoretical to application of soybean isoflavone aglycone in the intervention of osteoporosis. and confirmed that could replace chemical synthetic estrogen drugs.

Effects of lactic acid bacteria fermentation on the physicochemical and structural characteristics of starch in blends of glutinous and japonica rice.

In this study, the effects of lactic acid bacteria (LAB) fermentation on the physicochemical and structural characteristics of mixed starches in blends of glutinous and japonica rice were investigated. Five starter cultures improved in varying degrees the hydration ability, transparency, and freeze-thaw stability of the mixed starches. Mixed starch I, prepared by fermentation of Lactobacillus acidophilus HSP001, exhibited optimal water-holding capacity, solubility, and swelling power. In comparison, mixed starches V and III involved fermentation of L. acidophilus HSP001 and Latilactobacillus sakei HSP002, using ratios of 2:1 and 1:1 to achieve higher transparency and freeze-thaw stability, respectively. The LAB-fermented, mixed starches exhibited excellent pasting properties due to their high peak viscosities and low setback values. Moreover, the viscoelasticity of mixed starches III-V, prepared by compound fermentation of L. acidophilus HSP001 and L. sakei HSP002 in ratios of 1:1, 1:2, and 2:1, respectively, proved superior to their single strain fermentation counterparts. Meanwhile, LAB fermentation resulted in reduced gelatinization enthalpy, relative crystallinity, and short-range ordered degree. Thus, the effects of five LAB starter cultures on mixed starches were inconsistent, but these results provide a theoretical basis for the application of mixed starches. PRACTICAL APPLICATION: Lactic acid bacteria was used to ferment blends of glutinous and japonica rice. Fermented mixed starch had better hydration, transparency, and freeze-thaw stability. Fermented mixed starch exhibited nice pasting properties and viscoelasticity. LAB fermentation corroded starch granules, leading to the decrease of ΔH. Relative crystallinity and short-range order of fermented mixed starch decreased.

Effect of high-pressure homogenization on Ca2+ -induced gel formation of soybean 11 S globulin.

BACKGROUND: High-pressure homogenization (HPH) is commonly used as a non-thermal processing technique for soybean and soy protein products, and the preparation of soy protein gel products often requires the synergistic effect of HPH and heat treatment. The dissociative association behavior of 11 S is the key to the protein gel formation state. In this study, therefore, 11 S thermal gels were prepared by high-pressure homogenization and co-induction (90 °C, 30 min) (adding Ca2+ to promote gel formation before heat treatment), and the effects of different high-pressure homogenization pressures (0-100 MPa) and co-treatment on the dissociative association behavior of 11 S protein, gel properties, and microstructure of 11 S gels were investigated. RESULTS: The results showed that HPH at higher pressures led to the breaking of disulfide bonds of aggregates and disrupted non-covalent interactions in protein aggregates, leading to collisions between protein aggregates and the reduction of large protein aggregates. High-pressure homogenization treatment at 60 MPa improved the gel properties of 11 S more. The HPH combined with heating changed the binary and tertiary structure of 11 S soy globulin and enhanced the hydrophobic interaction between 11 S molecules, thus improving the gel properties of 11 S. The change in intermolecular forces reflected the positive effect of HPH treatment on the formation of denser and more homogeneous protein gels. CONCLUSION: In conclusion, high-pressure homogenization combined with heating can improve the properties of 11 S gels by changing the structure of 11 S protein, providing data and theoretical support for soy protein processing and its further applications. © 2022 Society of Chemical Industry.

Effects of Concentration of Soybean Protein Isolate and Maltose and Oil Phase Volume Fraction on Freeze-Thaw Stability of Pickering Emulsion.

There is growing interest in enhancing the freeze-thaw stability of a Pickering emulsion to obtain a better taste in the frozen food field. A Pickering emulsion was prepared using a two-step homogenization method with soybean protein and maltose as raw materials. The outcomes showed that the freeze-thaw stability of the Pickering emulsion increased when prepared with an increase in soybean protein isolate (SPI) and maltose concentration. After three freeze-thaw treatments at 35 mg/mL, the Turbiscan Stability Index (TSI) value of the emulsion was the lowest. At this concentration, the surface hydrophobicity (H0) of the composite particles was 33.6 and the interfacial tension was 44.34 mN/m. Furthermore, the rheological nature of the emulsions proved that the apparent viscosity and viscoelasticity of Pickering emulsions grew with a growing oil phase volume fraction and concentration. The maximum value was reached in the case of the oil phase volume fraction of 50% at a concentration of 35 mg/mL, the apparent viscosity was 18 Pa·s, the storage modulus of the emulsion was 575 Pa, and the loss modulus was 152 Pa. This research is significant for the production of freeze-thaw resistant products, and improvement of protein-stabilized emulsion products with high freeze-thaw stability.

Proliferation of Bifidobacterium L80 under different proportions of milk protein hydrolysate.

The intestinal microecological environment is critical to an infant's growth. For those infants consuming milk power, it is very important to improve the intestinal microecological environment to promote the healthy growth of infants. In this paper, Milk protein hydrolysate (MPH), consisting of different proportions of proteins and small molecule peptides (5:5, 4:6, 3:7, 2:8, 1:9) were added to infant formula powder (IFP). The effects of MFP-enriched IFP addition on proliferation and metabolism of Bifidobacterium L80 were studied. Compared with MPH-free IFP, MFP-enriched IFP with 1:9 of proteins to small molecule peptides significantly enhanced the proliferation of Bifidobacterium L80, resulting in higher cell density, greater viable counts and higher titratable acidity. MFP-enriched IFP increased the content of seven organic acids and H2O2 in the system, and improved the antibacterial activity to E. coli BL21. This study suggested that MPH could be an effective addition to infant formula powder to promote the growth of Bifidobacterium, so to improve the intestinal health of infants.

A Time Division Multiplexing Inspired Lightweight Soft Exoskeleton for Hip and Ankle Joint Assistance.

Exoskeleton robots are frequently applied to augment or assist the user's natural motion. Generally, each assisted joint corresponds to at least one specific motor to ensure the independence of movement between joints. This means that as there are more joints to be assisted, more motors are required, resulting in increasing robot weight, decreasing motor utilization, and weakening exoskeleton robot assistance efficiency. To solve this problem, the design and control of a lightweight soft exoskeleton that assists hip-plantar flexion of both legs in different phases during a gait cycle with only one motor is presented in this paper. Inspired by time-division multiplexing and the symmetry of walking motion, an actuation scheme that uses different time-periods of the same motor to transfer different forces to different joints is formulated. An automatic winding device is designed to dynamically change the loading path of the assistive force at different phases of the gait cycle. The system is designed to assist hip flexion and plantar flexion of both legs with only one motor, since there is no overlap between the hip flexion movement and the toe-offs movement of the separate legs during walking. The weight of the whole system is only 2.24 kg. PD iterative control is accomplished by an algorithm that utilizes IMUs attached on the thigh recognizing the maximum hip extension angle to characterize toe-offs indirectly, and two load cells to monitor the cable tension. In the study of six subjects, muscle fatigue of the rectus femoris, vastus lateralis, gastrocnemius and soleus decreased by an average of 14.69%, 6.66%, 17.71%, and 8.15%, respectively, compared to scenarios without an exoskeleton.

The influence of soy protein hydrolysate (SPH) addition to infant formula powder on Streptococcus thermophilus proliferation and metabolism.

Nowadays, more and more infants are getting allergic to cow's milk protein, so it is urgent to search for infant formula powder with milk protein alternatives. In the present work, soy protein hydrolysate (SPH) was added to protein-free infant formula powder and the effects of SPH addition on proliferation and metabolism of Streptococcus thermophilus were studied. Compared with commercially available infant formula powder (CK) and protein-free milk powder (BK), the infant formula powder with 20% SPH significantly enhanced the proliferation of S. thermophilus in MRS medium, resulting in a higher cell density and greater viable counts. Moreover, the influence of SPH on the metabolism of S. thermophilus was investigated by analyzing the content of seven organic acids and H2O2 in the medium. The higher content of organic acids and H2O2 is consistent with the stronger antibacterial activity to Escherichia coli. As a consequence, the addition of SPH to infant formula powder can effectively promote the growth of probiotics and SPH may be a promising protein alternative in the infant formula powder.

HS-GC-IMS with PCA to analyze volatile flavor compounds across different production stages of fermented soybean whey tofu.

The variations in flavor substances across the different stages of fermented soybean whey tofu (FSWT) production were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with principal component analysis (PCA). The results revealed 24 representative flavor compounds in the samples across all production stages. After heating, the signal intensity of hexanal, 1-octen-3-ol, heptanal, and (E)-2-hexenol, which are unpleasant flavor substances found in raw soymilk, weakened, whereas those of some aroma substances increased. Furthermore, fermented flavor compounds, namely, 2-heptanone, 2-pentylfuran, pentanal, and 2,3-butanedione, were produced after the addition of fermented soybean whey as a coagulant. A PCA based on the signal intensity of the detected volatile compounds revealed effective differentiation of samples from different stages into comparatively independent spaces. These results showed that the flavor fingerprints of the samples from different stages of FSWT production can be successfully built using HS-GC-IMS and PCA based on the detected volatile compounds.

Effects of soy protein isolate hydrolysates on cholecystokinin released by rat intestinal mucosal cells and food intake in rats.

Soy protein isolate hydrolysates (SPIH) were prepared from soy protein isolate (SPI). Effects of SPIH on a satiety signal cholecystokinin (CCK) and feeding behavior in rats were investigated. SPIH induced more CCK release (164.66 ± 2.40 pg/mL) by rat intestinal mucosal cells than SPI (143.33 ± 3.71 pg/mL). Meal size (MS), intermeal interval (IMI), and satiety ratio (SR = MS/IMI) of rats received different daily doses of SPIH or dietary fiber were detected for 40 days. A 100 mg/kg dose of SPIH resulted in a greater SR than an identical dose of dietary fiber, while a 300 mg/kg dose resulted in a less MS and IMI. A 500 mg/kg dose of SPIH had similar effects to the same dose of dietary fiber on reducing MS, extending IMI, and increasing SR, but resulted in a significantly less body weight at the end of the experiment (318.15 ± 17.83 g) than the dietary fiber group (340.28 ± 6.15 g).

Ultrasound-Assisted Mild Heating Treatment Improves the Emulsifying Properties of 11S Globulins.

Ultrasonic technology is often used to modify proteins. Here, we investigated the effects of ultrasound alone or in combination with other heating methods on emulsifying properties and structure of glycinin (11S globulin). Structural alterations were assessed with Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), intrinsic fluorescence spectroscopy, ultraviolet (UV) absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The size distribution and zeta-potential of 11S globulin were evaluated with a particle size analyzer. An SDS-PAGE analysis showed no remarkable changes in the primary structure of 11S globulin. Ultrasound treatment disrupted the 11S globulin aggregates into small particles with uniform size, narrowed their distribution and increased their surface charge density. Fluorescent spectroscopy and second-derivative UV spectroscopy revealed that ultrasound coupled with heating induced partial unfolding of 11S globulin, increasing its flexibility and hydrophobicity. FTIR further showed that the random coil and α-helix contents were higher while ß-turn and ß-sheet contents were lower in ultrasound combined with heating group compared to the control group. Consequently, the oil-water interface entirely distributed protein and reduced the surface tension. Moreover, ultrasound combined with heating at 60 °C increased the emulsifying activity index and emulsifying stability index of 11S globulins by 6.49-folds and 2.90-folds, respectively. These findings suggest that ultrasound combined with mild heating modifies the emulsification properties of 11S globulin.

Effects of casein non-phosphopeptide on the development of rat muscle analyzed using computed tomography scanning technology.

The effects of casein non-phosphopeptide (CNPP) on the muscle development of healthy rats and selected blood hormones levels were investigated. CT technology and the ELISA kit were employed to detect the cross-sectional area of each muscle group and blood hormone levels, respectively. The cross-sectional area of the trunk and lower limb muscles of resistance exercise group (REG) rats that were administered a high daily dose of CNPP for 50 days increased more significantly than that of the blank group rats, no exercise group (NEG) rats administered with the same daily dose of CNPP, and REG rats administered with the same daily dose of lactalbumin (P < 0.05).The more enhanced development of trunk and lower limb muscles in CNPP-administered REG rats was associated with a higher blood level of insulin, while no clear trends in blood levels of growth hormone and testosterone were observed. The present results have demonstrated that a combination of physical exercise and diet supplementation with CNPP can synergistically improve muscle mass.

Changes in morphology and activity of transglutaminase following cross-linking and immobilization on a polypropylene microporous membrane.

Transglutaminase (TGase) was cross-linked with glutaraldehyde, and cross-linked crystalline transglutaminase was immobilized on a polypropylene microporous membrane by UV-induced grafting. Immobilized enzyme activity were calculated to be 0.128 U/cm² polypropylene microporous membrane. The microstructure and enzyme characteristics of free, cross-linked and immobilized transglutaminase were compared. The optimum temperature of free transglutaminase was determined to be approximately 40 °C, while cross-linking and immobilization resulted in an increase to approximately 45 °C and 50 °C. At 60 °C, immobilized, cross-linked and free transglutaminase retained 91.7 ± 1.20%, 63.2 ± 1.05% and 37.9 ± 0.98% maximum activity, respectively. The optimum pH was unaffected by the state of transglutaminase. However, the thermal and pH stabilities of cross-linked and immobilized transglutaminase were shown to increase.