In vitro digestion mimicking conditions in adults and elderly reveals digestive characteristics of pork from different cooking ways.

This study aimed to investigate the impact of three cooking ways (sous vide (SV), frying (FR) and roasting (RO)) on pork protein digestion characteristics under conditions simulating healthy adult (control, C) and elderly individuals with achlorhydria (EA). Changes in degree of hydrolysis (DH), SDS-PAGE profiles, zeta potential, particle size and secondary structure during digestion were evaluated. Our results revealed the EA condition markedly affected the protein digestion process of pork with different cooking ways. The DH values of SV (25.62%), FR (21.38%) and RO (19.40%) under the EA condition were significantly lower than those of under the control condition (38.32%, 33.00% and 30.86%, respectively). Moreover, differences were also observed among three cooking ways under the EA condition. For a given cooking way, the differences between control and EA conditions gradually diminished from the gastric to the intestinal phase. Under a certain digestion condition, SV maintained the highest degree of digestion throughout the process, particularly under the EA condition. Therefore, we conclude that pork cooked by sous vide is more recommendable for the elderly considering protein digestibility.

Improved emulsifying properties of water-soluble myofibrillar proteins at acidic pH conditions: Emphasizing pH-regulated electrostatic interactions with chitosan.

Water-soluble muscle protein with enhanced functionalities has attracted great interest for low-salt food design. Electrostatic interactions of chitosan (CS) with myofibrillar proteins (MP) in water-aqueous solution at acidic pHs (4.0-6.5) were investigated, and how pH regulated complex formation, microstructures, conformation changes, and emulsifying capacity was systematically explored. At pH 4.0-4.5, MP and CS were positively charged and displayed a co-soluble system, exhibiting small particles and high solubility. When the pH increased to near the isoelectric point (pI) of MP (pH 5.0-6.0), electrostatic interactions largely inhibited the aggregation of MP by forming smaller particle complexes. The flexible structures and improved amphiphilic properties promoted protein absorption at the oil-water interface, further improving the emulsion stability. When the pH increased to 6.5, large aggregates were formed causing poor functionalities. This study could provide great insights to further exploit meat-protein-based low-salt functional foods in novel food design.

Effects of ultrasound-assisted intermittent tumbling on the quality of cooked ham through modifying muscle structure and protein extraction.

BACKGROUND: Tumbling treatment is widely used in the production of cooked ham. However, traditional intermittent tumbling (IT) treatment is time-consuming. To enhance the tumbling efficiency, high-intensity ultrasound was used to assist IT treatment (UIT). RESULTS: UIT treatment reduced the tumbling time and significantly improved the water holding capacity, tenderness, sliceability and texture of cooked ham compared to IT treatment. Furthermore, more violent destruction of meat tissue was exhibited in the UIT treatment. This change facilitated extraction of more salt-soluble protein, which in turn welded meat pieces tightly and improved the quality of the cooked ham. CONCLUSION: UIT treatment could accelerate the tumbling process and enhance the quality of cooked ham. These results may provide guidance on effective strategies for a high-quality meat production process. © 2023 Society of Chemical Industry.

The evaluation of mixed-layer emulsions stabilized by myofibrillar protein-chitosan complex for delivering astaxanthin: Fabrication, characterization, stability and in vitro digestibility.

Muscle protein based functional foods have been attracted great interests in novel food designing. Herein, myofibrillar protein (MP)-chitosan (CH) electrostatic complexes were employed to fabricate mixed-layer emulsions to protect and deliver astaxanthin. The MP/CH complex fabricated mixed-layer emulsions displayed higher stability against pH and temperature changes, exhibiting smaller droplet and homogenous distributions. After UV-light irradiation for 8 h, the mixed-layer emulsions had higher astaxanthin retention (69.11 %, 1:1 group). During storage, a lower degree of lipid oxidation, protein oxidation and higher astaxanthin retention were obtained, indicating desirable protections of mixed-layer emulsions. The vitro digestion reveled the mixed-layer emulsions could decrease the release of free fatty acids. Meanwhile, the bioaccessibility of astaxanthin was higher (30.43 %, 2:1 group) than monolayer emulsion. In all, the MP/CH prepared mixed-layer emulsions could protect and deliver fat-soluble bioactive compounds, and contributed to develop muscle protein based functional foods to meet the needs of slow and controlled release.

Analysis of the suitable thawing endpoint of the frozen chicken breast using video recording analysis, shear force, and bioelectrical impedance measurement.

This study focuses on analyzing the texture properties and bioelectrical impedance characteristics of frozen chicken breasts during low-temperature thawing, meanwhile, we also compared the differences in physiochemical properties. Frozen chicken breasts were thawed at 4 ± 2°C for 2, 4, 6, 8, and 10 h separately, then the physiochemical properties (color, pH, water-holding capacity, water distribution), the texture properties (easy-to-cut level), and the bioelectrical impedance were determined and analyzed. The easy-to-cut level of the samples was evaluated by the sensory panel and two indexes, one is Warner-Bratzler shear force measured by texture analysis machine, and the other is cutting speed value calculated by the consumer-oriented cutting behavior analysis using frame-by-frame video recording analysis method. These two methods were used to characterize the easy-to-cut level of the frozen samples during thawing from the industrial processing and home cooking standpoint. Strong correlations were observed between the easy-to-cut level and the bioelectrical impedance of the frozen chicken breasts during thawing. The impedance magnitude at 100 kHz showed a high correlation coefficient (R2 = .9417) with Warner-Bratzler shear force, and the impedance magnitude at 50 Hz showed a high correlation coefficient (R2 = .8658) with cutting speed. Our results indicated the acceptability of using bioelectrical impedance to evaluate the easy-to-cut thawing endpoint for both industry processing and home cooking.

The Differences in Protein Degradation and Sensitization Reduction of Mangoes between Juices and Pieces Fermentation.

Given the allergic reaction caused by mangoes, nonthermal food technologies for allergenicity reduction are urgently desired. This study aimed to assess the impact of kombucha fermentation on the allergenicity of mangoes. The total proteins, soluble proteins, peptides, amino acid nitrogen, the SDS-PAGE profiles of the protein extracts, and immunoreactivity of the sediment and supernatant were measured in two fermentation systems (juices and pieces fermentation). Throughout the fermentation, the pH decreased from about 4.6 to about 3.6, and the dissolved oxygen reduced about 50% on average. However, the protein degradation and sensitization reduction of mangoes were different between the two fermentation systems. In juices fermentation, there was a drop in proteins and peptides but an increase in amino acids, due to the conversion of proteins and peptides into amino acids both in the supernatant and sediment. The allergenicity decreased both in the solid and liquid phases of juices fermentation. In pieces fermentation, proteins and peptides were decreased in the solid phase but increased in the liquid phase. This was due to the fact that proteins and peptides were partly transported into the culture liquid, resulting in a decrease of allergenicity in fruit pieces and an increase in culture liquid. The principal component analysis results showed that the fermentation type had significant effects on the protein degradation and sensitization reduction, while mango variety had no significant effect. These results demonstrate that kombucha fermentation can reduce the allergenicity of mangoes, and it is more effective in juices fermentation than in pieces fermentation. The present study provides a theoretical basis for developing hypoallergenic mango products.

Effect of probiotic Bacillus cereus DM423 on the flavor formation of fermented sausage.

Insufficient protein and fat hydrolysis capacity of lactic acid bacteria (LAB) limit the flavor formation of fermented sausage. Bacillus is known for its substantial expression of proteases and lipases. However, its application in meat fermentation remains underexplored. In this study, a strain of probiotic Bacillus cereus (B. cereus DM423) was employed as a co-starter to improve the quality of Lactiplantibacillus plantarum (L. plantarum HH-LP56) fermented sausage. The addition of DM423 did not interfere with regular fermentation, but it significantly improved the flavor, as measured by electronic tongue and electronic nose. Further analyses using SDS-PAGE and thin-layer chromatography observed enhanced hydrolysis of protein and fat in sausages in which DM423 was involved in fermentation. GC-IMS identified DM423 mediated upregulation of various flavor compounds, including esters, ketones, furans, and branched-chain fatty acids. In addition, genomic de novo sequencing revealed that DM423 carried an abundance of genes associated with proteolysis, lipolysis, and the production of flavor substances, whereas HH-LP56 lacked these genes. Overall, this study finds that B. cereus DM423 can promote flavor formation in fermented sausages. It may illuminate a promising direction for the development of sausage co-starters from a wider microbial pool.

Influence of hydrophilic polysaccharide fat replacers on the in vitro digestibility of protein in emulsion-type sausage.

Hydrophilic polysaccharides have been widely applied as fat replacers in meat products, but their effects on the digestibility of meat proteins has seldom been studied. Replacement of backfat in emulsion-type sausage with konjac gum (KG), sodium alginate (SA) and xanthan gum (XG) were found to reduce the released amino group (-NH2) during simulated gastric digestion and initial intestinal digestion. The suppressed gastric digestibility of protein was verified by the denser structures of protein gastric digests and reduced generation of peptides in gastric digestion when a polysaccharide was added. After the whole gastrointestinal digestion, high level of SA and XG resulted in larger digests and a more obvious SDS-PAGE band between 5 and 15 kDa, and KG and SA significantly reduced the total release of -NH2. Additional of KG, SA and XG were found to the increase the viscosity of the gastric digests mixture, which could account for the reduced hydrolysis efficiency of pepsin during the gastric digestion, as evidenced in the pepsin activity study (decreased by 12.2-39.1%). This work highlights the influence of polysaccharide fat replacer on the digestibility of meat protein by changing the matrix characteristics.

A comparison of the impacts of different polysaccharides on the sono-physico-chemical consequences of ultrasonic-assisted modifications.

This study aimed to examine the sono-physico-chemical effects of ultrasound (UND) and its impact on the conjugate rates of morin (MOI) following the addition of polysaccharides in various conditions. In comparison to the control group, the incorporation of quaternary ammonium chitosan decreased the rate of MOI conjugation by 17.38%, but the addition of locust bean gum enhanced the grafting rate by 29.89%. Notably, the highest degree of myofibrillar protein (MRN) unfolding (fluorescence intensity: 114435.50), the most stable state (-44.98 mV), and the greatest specific surface area (393.06 cm2/cm3) were observed in the UMP/LBG group. The outcomes of atomic force microscopy and scanning electron microscopy revealed that the inclusion of locust bean gum led to a different microscopic morphology than the other two polysaccharides, which may be the primary cause of the strongest sono-physico-chemical effects of the system. This work demonstrated that acoustic settings can be tuned based on the characteristics of polysaccharides to maximize the advantages of sono-physico-chemical impacts in UND-assisted MOI processing.

Nonlinear Energy Harvesting by Piezoelectric Bionic 'M' Shape Generating Beam Featured in Reducing Stress Concentration.

Inspired by the flapping wings of seagulls during flight, a new low-cost, magnet-free, bistable piezoelectric energy harvester is proposed to obtain energy from low-frequency vibration and convert it into electrical energy and reduce fatigue damage caused by stress concentration. In order to optimize the power generation efficiency of this energy harvesting, finite element analysis and experimental tests were carried out. The results of finite element analysis and experimental results are in good agreement, and the superior performance in improving stress concentration of the energy harvester compared to the previous parabolic (bow-shaped) one using bistable technology was quantitatively analyzed using finite element simulation, with a maximum stress reduction of 32.34%. The experimental results showed that under optimal operating conditions, the maximum open-circuit voltage of the harvester was 11.5 V, and the maximum output power was 73 µW. These results indicate that this is a promising strategy, which provides a reference for collecting vibrational energy in low-frequency environments.

Improvement of the emulsifying properties of mixed emulsifiers by optimizing ultrasonic-assisted processing.

Optimizing ultrasound (ULD)-assisted flavonoid modification is an important component of enhancing its application potential. In this work, diverse flavonoids, such as quercetin (Que), apigenin (Api), and morin (Mor), were used to modify protein in myofibrillar protein (MP)/cellulose nanocrystal (CN) complexes using ULD-assisted method. Compared with the MP/CNs group, the triiodide contents of MP-Que/CNs, MP-Api/CNs, and MP-Mor/CNs increased by 1175.84%, 479.05%, and 2281.50% respectively. The findings revealed that the actual intensity of ULD was drastically reduced by the molecular weight decrease of these flavonoids. For olive oil emulsions prepared with mixed emulsifiers, the low interfacial diffusion rates (0.03 mN·m·s-1/2) and weak emulsifying activity (8.33 m2/g) of the MP/CN complexes were significantly improved by the flavonoids after ULD-assisted treatment. Notably, the emulsions prepared using MP-Api/CNs contained smaller oil droplets and exhibited better emulsifying properties, compared to emulsions prepared with MP-Mor/CNs or MP-Que/CNs. This study is essential for ULD-assisted treatment since the processing impact may be increased by choosing the most suitable flavonoid.

Development of edible films by incorporating nanocrystalline cellulose and anthocyanins into modified myofibrillar proteins.

In this study, a myofibrillar protein (MP) system was used to investigate the film properties changes by adjusting the intensity of the interaction of proteins with other food components. The structure and rheological properties of several film-forming solutions were then determined. Furthermore, the structure of these composite films was examined using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The smooth and uniform surface acquired by scanning electron microscopy (SEM) substantiated the increased compatibility and continuity observed for films with greater food component interaction. In addition, the MP-based edible films with stronger food component interactions (the MP-Myr/ANT/NCC group) displayed superior mechanical (tensile strength: 6.68 MPa, elongation at break: 94.43%), water vapor barrier (10.01 × 10-9 g m-1 s-1 Pa-1), and ammonia sensitivity (total color difference: 17.00) capabilities compared to those of the other groups (the MP/ANT/NCC, MP-Lut/ANT/NCC, and MP-Que/ANT/NCC groups).

Biotinylated caffeic acid covalent binding with myofibrillar proteins in alkaline conditions: Identification of protein-phenol adducts and alterations in protein properties.

In this study, the effects of covalent interactions between myofibrillar proteins (MP) and caffeic acid (CA) were investigated. Protein-phenol adducts were identified by biotinylated caffeic acid (BioC) used as a substitution of CA. The total sulfhydryls and free amines content were decreased (p < 0.05). The α-helix structure of MP increased (p < 0.05) and MP gel properties enhanced slightly at low dosages of CA (10 and 50 µM), and both were impaired significantly (p < 0.05) at high dosages of CA (250 and 1250 µM). Two prominent adducts of myosin heavy chain (MHC)-BioC and Actin-BioC were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), which gradually increased at low concentrations of BioC (10 and 50 µM), and raised significantly at the concentration of 1250 µM. According to the correlation analysis, MHC-BioC and Actin-BioC adducts showed a significant negative correlation with gel properties, such as G', hardness, and water holding capacity (WHC) (p < 0.01), which indicated that the covalent interactions between MP and CA significantly affected the quality of meat products.

Effect of curcumin on the formation of polycyclic aromatic hydrocarbons in grilled chicken wings.

Organic macromolecules form carcinogenic and toxic substances such as polycyclic aromatic hydrocarbons (PAHs) under high temperature baking. Thus, this study investigated the effects and inhibition pathways of different curcumin concentrations (0.01, 0.05, 0.25, 0.3 mg/g) on seven PAHs in grilled chicken wings. The results demonstrated that curcumin concentrations displayed positive effects in inhibiting the formation of PAHs (16%-72%), increasing the total phenolic content (397.5-1934.4 mg/g) and free radical scavenging activity, and reducing TBARS values (31.15%-47.76%) and fatty acid content. Additionally, PCA and Pearson correlation analyses indicated that lipid oxidation (r = 0.42) and unsaturated fatty acids (r = 0.55) could promote the production of PAHs, while DPPH, ABTS and TPC could counteract their facilitation of PAHs. In conclusion, the addition of appropriate amounts of curcumin before grilling is a feasible strategy to reduce fat oxidation levels and the number of free radicals for the purpose of limiting PAHs content.

Effect of temperature fluctuation during superchilling storage on the microstructure and quality of raw pork.

The effect of different temperature fluctuations on the microstructure and quality of pork loins during superchilling storage was investigated. Based on the dynamic monitoring of ice crystal formation and melting in pork through cryomicroscope, the changes of ice crystals in pork were observed at different temperature points, and there was no obvious phase transition in pork at -3 °C for a short period of time, but the freeze-thaw cycles were obviously found in the samples of -3 ± 3 °C and -3 ± 5 °C groups. Results of microstructure observation showed that temperature fluctuations resulted in muscle fiber fracture and the decrease of water holding capacity of superchilling pork, where stronger temperature fluctuation showed more significant changes. The temperature fluctuation groups exhibited higher thiobarbituric acid reactive substances (TBARS) values after 20 days of storage, and contributed to the reduction of immobilized water and the increase of free water in raw pork, and had more serious drip loss. These indicated that increased temperature fluctuation promoted lipid oxidation and drip loss of pork during storage. This study provided supports to precise temperature control in cold chain logistics of raw meat.

Conformation changes and emulsifying properties of myofibrillar proteins in water: Effects of electrostatic interaction with chitosan.

Great interests have been attracted toward muscle protein in a water-soluble state with improved functionality for further designing meat protein fortified low-salt functional foods. In the present study, electrostatic interaction of chitosan (CH) with myofibrillar proteins (MP) in water aqueous solution was investigated, and the linked structure changes and emulsion stabilization of MP were studied. Results showed that the electrostatic interaction inhibited MP aggregation, and smaller particle size complexes were formed at pH 6.0, leading to the loss of ß-sheet contents and recovery of α-helix contents with decreasing MP/CH mixing ratio (5:1 and 1:1). The tertiary structure confirmed the conformation changes of MP in which more hydrophobic groups and active sulfhydryl groups were exposed (P < 0.05), and the fluorescence was also quenched. With decreasing mixing ratio, the droplet size of emulsion decreased (P < 0.05), while the absorbed protein content increased (P < 0.05). After 7 d of storage, complex at a ratio of 1:1 displayed desirable emulsion stability, which could be due to the improved emulsifying capacity, enhanced electrostatic repulsion and steric effects. These findings provide a better understanding of conformation changes of MP in water aqueous solution induced by electrostatic interactions at mild acidic pH and help to fabricate stable protein/polysaccharide emulsification systems for further developing meat protein-based functional food to deliver health.

Explore the mechanism of continuous cyclic glycation in affecting the stability of myofibrillar protein emulsion: The influence of pH.

Emulsifying properties are one of the important functional properties of myofibrillar protein (MP), and improving the stability of the MP emulsions under a wide range of pH conditions can help resist the effects of unfavourable acid-base factors during processing. Previously, the continuous cyclic wet heating glycation was carried out to successfully prepare the MP-glucose conjugates, and the present study explored mechanism of the conjugates to stabilize emulsions under different pH conditions. The results showed that MP aggregated by intermolecular hydrophobic interactions under acidic conditions, while electrostatic repulsion induced the stretching of molecular conformation, and the emulsifying performance was significantly (P < 0.05) improved under neutral and alkaline conditions. Compared with the control MP, the more flexible structures and higher solubility of glycated molecules promoted the adsorption at the oil-water interface with increasing pH, resulting in a more uniform distribution of smaller oil droplets, which enhanced the internal structures and improved the rheological properties of the emulsions; meanwhile, due to the stronger intermolecular electrostatic repulsion and the steric hindrance, the emulsions prepared by glycated MP exhibited better dynamic stability and storage stability, especially at pH 11.

A Study on the Mechanisms of Nanoparticle-Stabilized High Internal Phase Emulsions Constructed by Cross-Linking Egg White Protein Isolate with Different Transglutaminase Concentrations.

There is an increasing interest in the development of high internal phase emulsions (HIPE) stabilized by food-grade nanoparticles due to their potential applications in the food industry. In this study, cross-linked egg white protein isolates (cEPIs) are prepared by adding 10 u/g, 20 u/g, and 40 u/g of transglutaminase (TG), and the impacts of interface properties of cEPIs and emulsifying of HIPEs are investigated. Relative to the native EPI, the cEPIs have more irregular and agglomerated morphology, and the turbidity and hydrophobicity are significantly increased. The particle size and zeta potential of cEPIs considerably varied with the addition of TG. In HIPE, the formation, physical properties, and microstructure are characterized by visual observations, the Turbiscan stability index, and CLSM. The results indicated that stable and gel-like HIPEs are formed by cEPIs at oil internal phase (φ) values of 0.75-0.90. Especially for the enzyme additions of 20 u/g, the cEPIs had the best storage stability and the lowest TSI value (2.50) and formed a gel network structure at φ values of 0.9 microscopically. Overall, this study can enrich the theoretical frame of interface properties by enzyme treatment. Besides, it would be of great importance for the research of HIPE stabilized by cEPIs appropriate to be applied in food formulations.

Digestion Profiles of Protein in Edible Pork By-Products.

Edible pork by-products are widely consumed in many areas, whereas their digestion characteristics have rarely been evaluated. This work compared the digestibility of protein in boiled pork liver, heart, tripe and skin with tenderloin as a control. Cooked skin showed the highest digestibility in the simulated gastric digestion, whereas its gastric digests were less digested in the simulated intestinal stage. In contrast, cooked tripe showed the lowest gastric digestibility but relatively higher intestinal digestibility. All the edible by-products showed lower digestibility than tenderloin, especially for pork liver, in which large undigested fractions (>300 µm) could be observed. Corresponding to these results, larger amount of bigger peptides was found in the digests of pork liver and skin. In addition, peptides in tripe (average bioactive probability = 0.385) and liver digests (average bioactive probability = 0.386) showed higher average bioactive probability than other samples. Tripe digests contained the highest level of free Asp, Gln, Cys, Val, Phe, Pro, Ser, Thr, Ile and Asn, whereas heart digests contained the highest level of free Leu, Met and Arg. These results could help to reveal the nutrition value of pork by-products.

Three new phomalone derivatives from a deep-sea-derived fungus Alternaria sp. MCCC 3A00467.

Three new phomalone derivatives, phomalichenones E-G (1-3), and seven known analogues (4-10) were isolated from the cultures of a deep-sea-derived fungus Alternaria sp. MCCC 3A00467. Their structures were elucidated by spectroscopic methods, including the 1D and 2D NMR, and ECD spectrum. Among the compounds isolated, phomalichenone F (2) presented cytotoxic activity against human myeloma cancer U266 cells with IC50 value of 24.99 µg/mL. The most active compound, 10, showed cytotoxicity against U266, HepG2 and A549 cells with IC50 values of 13.26, 14.69 and 24.39 µg/mL, respectively.