The Effects of Assisted Freezing with Different Ultrasound Power Rates on the Quality and Flavor of Braised Beef.

This study investigated the effects of ultrasound-assisted immersion freezing (UIF) at different power rates (0, 200, 400, and 600 W) on the changes in beef quality and flavor after braising. The results demonstrated that UIF treatment at 400 W significantly reduced the juice loss (cooking loss decreased from 49.04% to 39.74%) and fat oxidation (TBARS value decreased from 0.32 mg/kg to 0.20 mg/kg) of braised beef. In addition, the tenderness (hardness value decreased from 5601.50 g to 2849.46 g) and color stability of braised beef were improved after UIF treatment. The flavor characteristics of braised beef were characterized using an electronic nose and an electronic tongue. The PCA analysis data showed that the cumulative contribution rates of the first and second principal components were 85% and 93.2%, respectively, with the first principal component accounting for a higher proportion. The UIF-400 W group had the highest concentration for the first principal component, and the differentiation was not significant compared to the control group. The total amino acid values of different power UIF treatment groups were improved compared to the AF treatment group, indicating that UIF can effectively reduce the losses caused by freezing. The results demonstrate that ultrasound-assisted freezing treatment is beneficial in enhancing the tenderness and flavor attributes of beef after braising, providing new insights into the processing of meat products with desirable quality characteristics.

Bioinspired self-healing injectable nanocomposite hydrogels based on oxidized dextran and gelatin for growth-factor-free bone regeneration.

Hydrogels with great biocompatibility, biodegradability, and mechanical properties, combined with osteoconductivity, osteoinductivity, and osteointegration as biomaterials for bone regeneration without adding exogenous growth factors and cells are highly appealing but challenging. Here, inspired by organic-inorganic analogues of natural bone tissue and the adhesion chemistry of mussels, nanocomposite hydrogels with self-healing, injectable, adhesive, antioxidant, and osteoinductive properties (termed GO-PHA-CPs) were constructed by Schiff base cross-linking between dopamine-modified gelatin (Gel-DA) and oxidized dextran (ODex). Furthermore, the hydrogel network was enhanced by the introduction of polydopamine-functionalized nanohydroxyapatite (PHA) by improving the interfacial compatibility between the rigid inorganic particles and the flexible hydrogel matrix. Bioactive cod peptides (CPs) with osteogenic activity from Atlantic cod were further incorporated into the nanocomposite hydrogel. As a result, the multicomponent nanocomposite hydrogel favored the adhesion and spreading of MC3T3-E1 cells. The increased ALP activity suggested that GO-PHA-CPs hydrogels contributed to the osteogenic differentiation of MC3T3-E1 cells. The suitability of GO-PHA-CPs hydrogels for enhancing bone regeneration in vivo was further confirmed by the rat femoral defect model. Our results indicate that the multifunctional GO-PHA-CPs nanocomposite hydrogels without growth factors are a promising and effective candidate material for bone regeneration.

Myosin heavy chain-derived peptide of Gadus morhua promotes proliferation and differentiation in osteoblasts and bone formation and maintains bone homeostasis in ovariectomized mice.

Gadus morhua is an important commercial fish rich in nutrients required for daily metabolism. However, the regulation of G. morhua peptides (GMP) on osteoblast growth remains unclear. In order to clarify the regulatory effects of GMP on osteoblasts, the effects of GMP on the growth of MC3T3-E1 cells were investigated, and the osteogenic peptides were identified and screened. The results showed that GMP promoted the proliferation and differentiation of osteoblasts by regulating the BMP/WNT signaling pathway at concentrations of 1-100 µg mL-1. Molecular docking studies showed that a decapeptide, MNKKREAEFQ (P-GM-1), had a high affinity for integrins 3VI4 and 1L5G (-CDOCKER interaction energy: 161.30, 212.27 kcal mol-1). Additionally, the proliferation rate of MC3T3-E1 cells was increased by 27%, and ALP activity was significantly increased under P-GM-1 treatment (100 µg mL-1). Moreover, P-GM-1 promotes bone formation, maintains bone homeostasis, and prevents osteoporosis in ovariectomized mice by regulating the BMP/Smad signaling pathway. This study confirmed the potential of GMP in the regulation of bone mineral density and provided a certain theoretical basis for the development of anti-osteoporosis active factors from GMP.

Gelatin hydrogel reinforced with mussel-inspired polydopamine-functionalized nanohydroxyapatite for bone regeneration.

Developing high-strength hydrogels with biocompatibility and bone conductibility is still desirable for bone regeneration. The nanohydroxyapatite (nHA) was incorporated into a dopamine-modified gelatin (Gel-DA) hydrogel system to create a highly biomimetic native bone tissue microenvironment. In addition, to further increase the cross-linking density between nHA and Gel-DA, nHA was functionalized by mussel-inspired polydopamine (PDA). Compared with nHA, adding polydopamine functionalized nHA (PHA) increased the compressive strength of Gel-Da hydrogel from 449.54 ± 180.32 kPa to 611.18 ± 211.86 kPa without affecting its microstructure. Besides, the gelation time of Gel-DA hydrogels with PHA incorporation (GD-PHA) was controllable from 49.47 ± 7.93 to 88.11 ± 31.18 s, contributing to its injectable ability in clinical applications. In addition, the abundant phenolic hydroxyl group of PHA was beneficial to the cell adhesion and proliferation of Gel-DA hydrogels, leading to the excellent biocompatibility of Gel-PHA hydrogels. Notably, the GD-PHA hydrogels could accelerate the bone repair efficiency in the rat model of the femoral defect. In conclusion, our results suggest the Gel-PHA hydrogel with osteoconductivity, biocompatibility, and enhanced mechanical properties is a potential bone repair material.

Strong fish gelatin hydrogels double crosslinked by transglutaminase and carrageenan.

Gelatin hydrogels are usually soft and thermally unstable. Here, strong fish gelatin hydrogels were successfully prepared by double crosslinking gelatin with transglutaminase (TGase) and κ-carrageenan, and the mechanical properties and thermal stability of the double crosslinked gelatin hydrogels were significantly improved. Results showed that the gel strength, compression fracture stress and storage modulus of the double crosslinked gelatin hydrogels all reached the largest value when the concentration of TGase was 20 U/g gelatin. The double crosslinked gelatin hydrogels were also thermally stable due to the existence of the covalent crosslinks. The effect of TGase concentration on the physical properties and microstructure of the double crosslinked hydrogels were analyzed, and the differences between double crosslinked gelatin hydrogels and gelatin hydrogels single crosslinked by TGase or carrageenan were also systematically compared. This article is of great significance for expanding the application of natural polymer-based hydrogels.

Optimization of Enzyme-Assisted Extraction and Purification of Flavonoids from Pinus koraiensis Nut-Coated Film and Antioxidant Activity Evaluation.

Pinus koraiensis nut-coated film is a kind of by-product of nut processing, which has been shown to contain flavonoids, polyphenols, and other substances that can be used to produce natural antioxidant extracts. In this study, response surface methodology (RSM) was used to optimize the extraction process of flavonoids of P. koraiensis nut-coated film (PNF), and macroporous resin HPD600 was used to purify PNF (P-PNF). Its antioxidant activity was examined by DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging capacity, oxygen free radical absorption capacity (ORAC), total oxygen radical capture (TRAP), and iron ion reduction capacity. Under the ideal extraction conditions comprising a cellulase dosage of 90 U/g, a material/liquid ratio of 1:20 (g/mL), and an extraction time of 2 h, the PNF yield was 3.37%. Purification conditions were sample concentration of 2.0 mg/mL, pH of 5, water washing volume of 3 bed volume (BV), eluent ethanol concentration of 50%, and volume of 2 BV. The P-PNF recovery was 84.32%, and purity increased from 33.80% to 61.70%. Additionally, P-PNF showed increased antioxidant activity compared to PNF. Cumulatively, this study obtained the optimal values for the process parameters in order to achieve the maximum rates of extraction of PNF for economically optimal production at an industrial scale.

Reduced Adhesive Force Leading to Enhanced Thermal Stability of Soy Protein Particles by Combined Preheating and Ultrasonic Treatment.

Developing liquid systems with high protein contents is drawing intensive attention; however, this is challenged by heat-induced aggregation and gelation of proteins. Herein, we described a facile but robust approach of combined preheating and ultrasonic treatment (CPUT) to fabricate soy protein particles (SPPs) with enhanced heat stability. Results showed that these heat-stable particles, upon reheating at 1% (w/v), showed antiaggregation property evidenced from no obvious changes of the particle size distributions of suspensions. Besides, no gelation was found in the reheated test for SPPs suspended even at a concentration of 10% (w/v). In contrast, the control formed sol-gel after heating. The rearrangements of soy protein molecules by CPUT led to the formation of SPPs with reduced surface energy, which was primarily responsible for their heat stability. These findings highlighted that the CPUT could prepare thermally stable soy proteins, providing insights into the application of soy proteins in protein-enriched beverages.

Advancement of food-derived mixed protein systems: Interactions, aggregations, and functional properties.

Recently, interests in binary protein systems have been developed considerably ascribed to the sustainability, environment-friendly, rich in nutrition, low cost, and tunable mechanical properties of these systems. However, the molecular coalition is challenged by the complex mechanisms of interaction, aggregation, gelation, and emulsifying of the mixed system in which another protein is introduced. To overcome these fundamental difficulties and better modulate the structural and functional properties of binary systems, efforts have been steered to gain basic information regarding the underlying dynamics, theories, and physicochemical characteristics of mixed systems. Therefore, the present review provides an overview of the current studies on the behaviors of proteins in such systems and highlights shortcomings and future challenges when applied in scientific fields.

Preheat-induced soy protein particles with tunable heat stability.

Recently, there is a growing interest in developing protein-enriched beverages with improved nutritional and functional properties. However, this is challenged by heat-induced aggregation and gelation of edible proteins, which limits their practical applications in high protein systems. In this study, soy protein particles (SPPs) with tunable heat stability were prepared by simply preheating soy proteins suspensions (pH 6.4 and 1% (w/v) concentration) at different temperatures and times. Results showed that heat-stabled SPPs were successfully obtained at high preheating temperatures with prolonged time. The SPPs structures were found to be highly unfolded, denatured, and compact. In addition, these particles exhibited lower viscosities and higher flow behavior index without gelation, whereas those prepared at lower preheating temperatures were found to readily gel after reheating. These results provide useful insights on how heat stable SPPs can be prepared, which extends their further application in protein-enriched beverages and relevant products.

The mechanism of improved thermal stability of protein-enriched O/W emulsions by soy protein particles.

Growing interest in nutritional and functional foods has motivated the design of protein-enriched products in the food industry, which, however, is greatly challenged by undesirable aggregation and gelation of proteins induced by heating from the pasteurization process. In this study, we reported the preparation of heat-stable soy protein particles (SPPs) by a simple preheating process (100 °C for 30 min) at pH 6.2 and 0.5% (w/v) protein concentration. As a proof of concept, the thermal stability of high-protein emulsions prepared by SPPs compared to native soy proteins (SPs) was investigated. The results showed that high-protein emulsions stabilized by SPPs exhibited appreciable heat stability, whereas SPs gelled when both samples were tested at an identical concentration (10%, w/v). In addition, the emulsions prepared by SPPs demonstrated lower values of storage modulus and viscosity along with a stable size by heat treatment as well as a more stable coated protein layer, in contrast to those prepared by SPs presenting macroscopic aggregation and an unstable coated protein layer. The results would provide valuable information in terms of the development of heat-stable, high-protein, and well-dispersed food emulsions that may find numerous applications in the food industry.

Enhancing the thermal stability of soy proteins by preheat treatment at lower protein concentration.

The heat-induced aggregation of edible proteins has been regarded as one of the critical challenges for their application in protein-enriched beverages. Therefore, the formulation of thermal stable proteins to improve the stability of these beverages upon heating is highly desired. In this study, soy proteins (SPs) with enhanced heat stability were obtained by low-concentration-preheating (LCPH). Results from reheating of the above samples showed that pretreatment of SPs at low concentrations (≤1.0%, w/v) increased their resistance against aggregation. Additionally, when the suspensions of the particles were reheated at 10% (w/v) protein concentration, no gelation was found for samples prepared by LCPH, indicating collapsed protein-protein interactions, whereas gelled suspensions were obtained for native SPs and samples prepared by preheating at higher protein concentrations (≥2.0%, w/v). Furthermore, suspensions of particles prepared at lower protein concentration showed lower viscosities and higher flow behavior index values before and after reheat treatment. These findings highlighted that LCPH would provide fundamental information on the application of SPs in high protein beverages.

Preheat-stabilized pea proteins with anti-aggregation properties.

Solution stability of food proteins is a crucial factor determining their shelf-life and sensory properties; yet to obtain stable protein products such as beverages is generally challenged by the growing demand for non-additive foods. Here, we report a facile method stabilizing pea proteins (PPs) by a simple preheating process at a concentration below 4% (w/v) and a temperature >90 °C. Far ultraviolet circular dichroism, fluorescence spectra, together with light scattering analyses demonstrated that the PPs were unfolded and became crosslinked via exposed hydrophobic moieties and disulfide bonds, giving rise to the formation a stable spatio-temporal interconnected system that could withstand the initial nucleation of aggregations. In addition, for reheated samples treated at a sufficiently high concentration of 15% (w/v), rheological characterizations revealed decreased aggregation along with increased preheating temperature and decreased preheating concentration. The robust strategy, along with the stabilized PPs in this study, would give a strong insight into preparation of heat-stable proteins with a wide span of concentrations, which may serve the needs for protein-enriched ingredients and satisfy the demands for cost-effective protocols applied in food industry.

A self-sorted gel network formed by heating a mixture of soy and cod proteins.

The development of binary protein networks featuring superior nutritional and rheological properties is an intriguing, as well as challenging, aspect in the food industry. In this study, a novel, self-assorted double protein network was constructed, which was achieved by simply heating soy protein (SP) and cod protein (CP) at 100 °C with different SP/CP ratios (5 : 0 to 0 : 5). Atomic force microscopy revealed that the heat-induced protein aggregate size increased with increasing CP ratio from 0 to 100%, which was accompanied by a significant increase in surface hydrophobicity and the content of disulfide bonds. Meanwhile, the ratio of non-network proteins in the gel network decreased significantly from 12.5 to 3.2% with the increase of the CP ratio from 0 to 100%. Concomitantly, the networks formed at a higher CP ratio were found to be less homogeneous and more porous with higher storage modulus. Interestingly, results from far-UV CD, near-UV CD, and fluorescence demonstrated that there were no interactions between SP and CP during thermal treatment, suggesting that the gel formed by mixed proteins was a self-sorted network. The study would advance the utilization of blended fish proteins and plant proteins toward tailor-made double networks that may find many applications in food and relevant areas.

Ultrasound treatment improved the physicochemical characteristics of cod protein and enhanced the stability of oil-in-water emulsion.

Effects of ultrasonic pretreatment on the physicochemical changes of cod protein and the characteristics of subsequent oil-in-water emulsions were investigated. Ultrasonic treatment led to a reduction of particle size of cod protein. With increasing ultrasonic power, a significant increase in surface hydrophobicity of cod protein was found, due to the decrease of aggregates size as well as protein conformational changes of protein, but a decrease in total sulfhydryl group content was observed, probably because of the formation of disulfide bonds. Ultrasonic pretreatment promoted the adsorption of cod protein on oil droplets, resulting in higher ratios of adsorbed proteins. Diagonal electrophoresis illustrated that larger aggregates in adsorbed proteins were composed of cod actin. Reducing SDS-PAGE showed that adsorbed proteins contained a large amount of cod actin and two faint bands of light chains of myosin, and non-adsorbed proteins were composed of actin, tropomyosin, and the three light chains of myosin. More homogenous microstructures with smaller size of oil droplets were observed for the emulsions stabilized by higher intensity ultrasound treated cod protein, and the coalescence effect was improved obviously. The enhancement of the stability of cod protein coated-oil emulsions might be due to the smaller size of oil droplets and reduced oil droplets attraction by higher ratios of adsorbed proteins.