Effects of constant power microwave on the adsorption behaviour of myofibril protein to aldehyde flavour compounds

Environmental factors and blueberry anthocyanin-induced conformational changes modulate the interaction between myofibrillar proteins and fishy compounds and their mechanism, specifically aldehydes and alcohols

This study investigated the impact of blueberry anthocyanin (BA) on the interaction between tilapia myofibrillar protein (MP) and fishy compounds (hexanal, octanal, nonanal, trans-2-nonenal, and 1-octen-3-ol). Results indicated that at a protein concentration of 5 mg/mL and fishy compounds at 5 μg/mL, MP effectively adsorbed these compounds at 4 °C, pH 7.0, and 0.6 mol/L Na+. Increasing BA concentration (0.03-0.24 mg/mL) enhanced the α-helix content of MP from 30 % to 60 %, with a blue shift in the maximum fluorescence emission peak (333-337 nm), suggesting that BA promotes protein structural folding and stability. In MP and fresh fish models, BA addition significantly decreased hexanal (from 50.2 % ± 1.6 % to 29.0 % ± 9.5 %), octanal (from 97.8 % ± 1.6 % to 38.7 % ± 1.8 %), and nonanal (from 69.4 % ± 7.7 % to 39.0 %). Conversely, higher BA concentrations led to increased release of 1-octene-3-ol (from 104.1 % ± 4.4 % to 120.4 % ± 1.1 %). Overall, the findings highlight the correlation between BA's effects on protein folding and stabilization and its influence on the controlled release of fishy compounds, underscoring the significance of polyphenols in protein-flavor interactions. This research offers valuable insights into flavor management and establishes a theoretical basis for flavor regulation in tilapia meat products, contributing to the broader study of quality control and flavor enhancement in meat products through natural pigment active ingredients.

A new method and mechanism for the rapid detoxification of the herb Pinelliae Rhizoma from the Araceae family, based on the dual destruction of raphides and lectin proteins

Pinelliae Rhizoma (PR), a traditional herbal medicine and dietary supplement, is valued for its cough relief and anti-inflammatory effects. However, it can cause significant throat irritation. And unfortunately, current processing techniques can lead to a considerable loss of active constituents in PR. This study employed microwave irradiation to process PR and elucidated the mechanisms underlying its attenuation of PR's irritation. The results demonstrated that microwave irradiation significantly enhanced the processing efficiency, reducing the traditional processing cycle from 5 to 15 days to just 10 min, while preserving active ingredients and mitigating irritation. Subsequent analysis of the irritant components found that microwave treatment significantly reduced the raphides content, altering their morphology. Concurrently, the secondary structure of lectin proteins underwent significant changes, including an increase in β-sheets, a decrease in β-turns and random coils content, and the formation of insoluble aggregates. In conclusion, microwave irradiation is an effective method for reducing the irritation of PR, with the mechanism attributed to the physical destruction of raphides and alterations in the hydrophobicity of lectin proteins. This study provides a novel approach and method for the processing and development of Araceae herbs, as well as food products such as yam, konjac, and pineapple.

Investigation of the interaction between collagen and furan derivatives during the heating process via multidimensional spectroscopy and GC-MS technology

The flavor retention plays a critical role in the presence of rich flavor profile of meat products. However, the interaction between collagen and furan derivatives has not been previously reported. In this study, the interaction between collagen and furan derivatives during heating was investigated using multidimensional spectroscopy and gas chromatography-mass spectrometry (GC-MS). The results revealed that the collagen structure was disrupted during the heating process, causing its depolymerization and an increase in the absolute value of zeta potential. The heating treatment induced a structural transformation in the collagen from large and ordered sheets to smaller and irregular aggregates. Meanwhile, the binding ability between collagen and furan derivatives was also significantly increased during the heating process due to the increased exposure of sulfhydryl groups and a rise in surface hydrophobicity. These findings will provide valuable insights into the retention of volatile compounds in the meat products.

Effect of bacterial fermentation on the ability of myofibrillar proteins to bind esters and its potential mechanism: Based on protein metabolism and structural changes

The effect of fermentation strains (Lactiplantibacillus plantarum CQ01107 and Staphylococcus simulans CD207) on the binding properties of porcine myofibrillar proteins (MPs) to esters was investigated from two perspectives: metabolism degree and structural alterations. Results demonstrated that S. simulans could reduce the particle size and α-helix content of MPs, while simultaneously increasing the absolute zeta potential and active sulfhydryl content. This process decreased protein aggregation and facilitated the unfolding of MPs, thereby enhancing their binding to esters. Conversely, L. plantarum showed limited promotion, which might be related to its robust acid production and protein hydrolysis capacities. In addition, ethyl octanoate, with a longer carbon chain length, was found to have the highest binding capacity to MPs (28.38 %-41.59 %). Molecular docking results further revealed that the binding of the four esters to MPs was spontaneous, with ethyl octanoate exhibiting the lowest binding energy to MPs (-5.635 kcal/mol). The primary forces involved in the binding of the four selected esters to MPs were hydrophobic interactions, hydrogen bonding, and van der Waals forces. These findings can provide new insights into the mechanisms by which fermentation strains influence flavor formation in fermented foods.

Effect of microwave treatment and water-bath heating treatment on the performance of glutenin from Tiger nut seed meal: Insights into changes in structural characteristics, functional properties, and in vitro gastrointestinal digestibility

In this study, the structural characteristics, functional properties, and in vitro gastrointestinal digestibility of glutenin from Tiger nut seed meal (TNSMG) treated by microwave (140-700 W, 20-60 s) and water-bath heating (40-100 °C, 10-30 min) were investigated. Analysis of the surface hydrophobicity, intrinsic fluorescence spectroscopy and Fourier transform infrared spectroscopy indicated that both microwave and water-bath heating treatments caused structure changes of TNSMG. The results showed an increase in the exposure of sulfhydryl groups and the content of β-sheet, coupled with a decrease in the content of α-helix and β-turn. These structural changes contributed to the improved solubility, foamability, emulsification properties, and digestibility of TNSMG under proper thermal treatment conditions. TNSMG exhibited the best solubility (68.48%) and foamability (85.56%) after water-bath heating treatment for 20 min at 80 °C. Furthermore, TNSMG showed the best emulsification property (9.61 m2/g) and digestibility (78.58%) when treated by microwave treatment at 560 W for 40 s.

Comparison and elucidation of the changes in the key odorants of precooked stewed beef during cooking-refrigeration-reheating

The key odorants contributing to the warmed-over flavor (WOF) of reheated precooked stewed beef were characterized using a sensomics approach. Overall, 36 odorants were identified, and based on flavor dilution factors, odor activity values, aroma recombination, and omission test, 11 compounds mainly derived from lipid oxidation were characterized as the key odorants contributing to the formation of WOF. In particular, 3-(methylthio)propanal, which was positively correlated with meaty aroma, was implicated in an overall increase in WOF. Thus, these odorants were elected as potential markers of WOF in the reheated precooked stewed beef. In summary, the WOF of the precooked stewed beef could be attributed to an overall increase in lipid oxidation products and a decrease in the odorants with desirable aromas. The characterization of WOF in precooked stewed beef will aid in the flavor quality control of precooked stewed beef dishes.

Unveiling differential impact of heat and microwave extraction treatments on the structure, functionality, and digestibility of jack bean proteins extracted under varying extraction pH

The poor extractability and digestibility of jack beans restrict their application in food systems. Thermal treatment could be a processing tool to disrupt the compact conformation of the plant matrix and inactivate inherent antinutrients. Therefore, this research investigated the impact of conventional heat-aided (HA-) and microwave-aided (MA-) extraction treatments on the structure, functional properties, and digestibility of jack bean protein concentrate (JBPC) under varying extraction pH. The novelty brought by the present study is establishing the thermal treatment/extraction pH combinations for improving techno-functionalities and digestibility of JBPC. Heat (50 °C for 1 h) and sequential microwave power (400 W, 600 W, and 800 W for 5 min) at three extraction pH (9.0, 10.0, and 11.0) were studied. Upon increasing extraction pH, a significant decrease in the protein content, and β-Sheet structure was observed, in the order of pH 11.0 > 10.0 > 9.0. JBPC extracted using HA treatments displayed the highest contents of surface hydrophobicity (90.02) and sulfhydryl groups. In functional properties, MA-extracted JBPC under 400 W showed significantly improved solubility (93.45 %), emulsifying activity index (45.23 m2/g), and foaming capacity (141.70 %) when compared to other thermal treatments. The degree of hydrolysis result revealed that MA treatment improved the JBPC in vitro digestibility at a low power level of 400 W. These findings suggest that MA extraction treatment can improve the functional and nutritional properties of JBPC regardless of the extraction pH, and thus, expand the potential application in food systems.

Zero-waste multistage utilization of dandelion root

Introduction

In the fragrance and perfume industry, the controlled release of fragrances are crucial factors that contribute to consumer appeal and product quality enhancement. In this study, various aromatic active substances were extracted from dandelion root (DR), which was subsequently calcined to produce high-performance porous biochar material.

Methods

The dandelion root biochar (DRB) material was identified as promising adsorbents for the controlled release of fragrances. Furfuryl alcohol was chosen as the model fragrance for inclusion and controlled release studies.

Results and discussion

The DRB exhibited a substantial specific surface area of 991.89 m2/g, facilitating efficient storage and controlled release capabilities. Additionally, the DRB's high stability and porous nature facilitated rapid collection and efficient recyclability. This research significantly contributes to the development of a sustainable, zero-waste multistage utilization strategy for dandelion roots, indicating a potential applications in the food flavoring industry and environmental conservations.

Proteomics reveals the mechanism of protein degradation and its relationship to sensorial and texture characteristics in dry-cured squid during processing

Proteolysis in dry-cured squid contributes to the development of sensory and textural attributes. In this study, label-free quantitative proteomics was conducted to study the mechanism of proteolysis and its correlation with quality changes. The results showed that the protein profile of dry-cured squid changed markedly during processing, which was confirmed by the quantification of myofibrillar protein, amino nitrogen and total free acids, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Thirty-two key differentially abundant proteins were found to be correlated with sensory and texture characteristics, including myofibrillar protein, tubulin beta chain, collagens, heat shock proteins and cytochrome c. The correlation analysis indicated that myosin regulatory light chain and tubulin beta chain played the most important role in the development of texture and sensory attributes in squid samples during the dry-curing process. The results offered novel insights into proteolysis in dry-cured squid and its relationship to quality changes.

Effect of ultrasound treatment on porcine myofibrillar protein binding furan flavor compounds at different salt concentrations

The effects of ultrasound (500 W) on the interaction of porcine myofibrillar protein (MP) with furan flavor compounds at different salt concentrations (0.6 %, 1.2 % and 2.4 %) were investigated. With the increase of salt concentration, the particle size of MP decreased, and the surface hydrophobicity and active sulfhydryl content increased due to the unfolding and depolymerization of MP. At the same time, ultrasound promoted the exposure of hydrophobic binding sites and hydrogen bonding sites of MP in different salt concentration systems, thus improving the binding ability of MP with furan compounds by 2 % to 22 %, among which MP had the strongest binding capacity of 2-pentylfuran. In conclusion, ultrasound could effectively promote the unfolding of the secondary structure of MP, which was beneficial to the combination of MP and furan flavor compounds under different salt concentrations.

Investigating the Mechanism of Microwave-Assisted Enzymolysis Synergized with Magnetic Bead Adsorption for Reducing Ovalbumin Allergenicity through Biomass Spectrometry Analysis

This study found that, after microwave treatment at 560 W for 30 s, alkaline protease enzymolysis significantly reduced the allergenicity of ovalbumin (OVA). Furthermore, specific adsorption of allergenic anti-enzyme hydrolyzed peptides in the enzymatic products by immunoglobulin G (IgG) bound to magnetic bead further decreased the allergenicity of OVA. The results indicated that microwave treatment disrupts the structure of OVA, increasing the accessibility of OVA to the alkaline protease. A comparison between 17 IgG-binding epitopes identified through high-performance liquid chromatography-higher energy collisional dissociation-tandem mass spectrometry and previously reported immunoglobulin E (IgE)-binding epitopes revealed a complete overlap in binding epitopes at amino acids (AA)125-135, AA151-158, AA357-366, and AA373-381. Additionally, partial overlap was observed at positions AA41-59, AA243-252, and AA320-340. Consequently, these binding epitopes were likely pivotal in eliciting the allergic reaction to OVA, warranting specific attention in future studies. In conclusion, microwave-assisted enzymolysis synergized with magnetic bead adsorption provides an effective method to reduce the allergenicity of OVA.

Characterization of the odor compounds in human milk by DHS/GC × GC-O-MS: A feasible and efficient method

Odor analysis of human milk (HM) is often challenging. Here, a new strategy for the analysis of odorants in HM using dynamic headspace sampling combined with comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry (DHS/GC × GC-O-MS) was established based on the comparison of different extraction methods and instrument modes. Overall, DHS/GC × GC-O-MS was proved to be able to provide higher extraction efficiency and better analytical results of the odor-active compounds (OACs) in HM, meanwhile, the salt addition during the extraction further promoted the release of the odorants. Twenty key OACs in HM were identified by flavor dilution analysis and odor activity calculation, of which 1-octen-3-one, 2,3-butanedione, (E)-2-nonenal, and nonanal contributed significantly to the odor of HM. In addition, 2,3-pentanedione was detected as a key OAC in HM for the first time. This study provided a powerful analytical strategy for the comprehensive odor analysis of HM.

Comprehensive binding analysis of glycated myosin with furan derivatives via glucose by means of multi-spectroscopy techniques and molecular docking simulation

Myosin is an ideal binding receptor for aroma compounds and its functional properties are easily affected by glucose. The study comprehensively clarified the effects of glucose glycation-induced structural modifications of myosin on its binding ability with furan derivatives, including 2-methylfuran, 2-furfural, and 2-furfurylthiol. The results demonstrated that the binding levels of furan derivatives were obviously affected by the glycation levels of myosin due to the changes of myosin structure and surface. The increased glycation levels caused the unfolding of myosin structure and accelerated the aggregation, as were exhibited by the data of zeta potential, particle size, microstructure, and secondary structure. The glycated myosin with wrinkled surfaces favored the significant increase of hydrophobic interactions (31.59-69.50 μg), the more exposure of amino acid residues (3459-6048), the formation of free sulfhydryl groups (16.37-20.58 mmol/104g) and hydrogen bonds. These key (non)covalent linkages accounted for the generation of glycated myosin-odorants complex, including 2-furfurylthiol (29.17-47.87 %), thus enhancing the resultant binding ability as evidenced by the free furan derivatives concentrations, fluorescence quenching and molecular docking simulation analysis. The glycated myosin for 8 h bound highest concentrations of furan derivatives. The results will provide comprehensive data on the retention of aroma compounds in meat products.

Effect of Process Variables and Ingredients on Controlled Protein Network Creation in High-Moisture Plant-Based Meat Alternatives

The market has observed a rapid increase in the demand for plant-based foods as an alternative to animal meat products. Technologies such as high-moisture extrusion (HME) have the potential to develop anisotropic structures using alternative protein ingredients. This article discusses the different possible mechanisms responsible for structure formation and the effect of extrusion process parameters and outlines the recent advances in the long cooling dies (LCDs) used for meat alternative development. The role of different protein ingredients and the impact of combining them with other biopolymers were also evaluated. The underlying mechanism behind anisotropic structure formation during HME is a synergistic effect, with substantial dependence on the source of ingredients and their processing background. Formulation including proteins derived from plants, insects, animals, and microalgae with other biopolymers could pave the way to develop structured meat alternatives and fill nutritional interstices. Dynamic or rotating annular gap cooling dies operating at freely controllable shear and static annular gap dies are recent developments and assist to produce layered or fibrous structures. The complex chemical sites created during the HME of plant protein favour flavour and colour retention. This paper summarises the recent information published in the scientific literature and patents, which could further help researchers to fill the present knowledge gaps.

Mechanism of the Allergenicity Reduction of Ovalbumin by Microwave Pretreatment-Assisted Enzymolysis through Biological Mass Spectrometry

Ovalbumin (OVA) is a major allergen in hen eggs. Enzymolysis has been demonstrated as an efficient method for reducing OVA allergenicity. This study demonstrates that microwave pretreatment (MP) at 400 W for 20 s assisting bromelain enzymolysis further decreases the allergenicity of OVA, which was attributed to the increase in the degree of hydrolysis and promoted the destruction of IgE-binding epitopes. The results showed that MP could promote OVA unfolding, expose hydrophobic domains, and disrupt tightly packed α-helical structures and disulfide bonds, which increased the degree of hydrolysis by 7.28% and the contents of peptides below 1 kDa from 43.55 to 85.06% in hydrolysates compared with that for untreated OVA. Biological mass spectrometry demonstrated that the number of intact IgE-binding epitope peptides in MP-assisted OVA hydrolysates decreased by 533 compared to that in hydrolysis without MP; consequently, their IgG/IgE binding rates decreased more significantly. Therefore, MP-assisted enzymolysis may provide an alternative method for decreasing the OVA allergenicity.

Influence of Multi-Frequency Ultrasound Treatment on Conformational Characteristics of Beef Myofibrillar Proteins with Different Degrees of Doneness

This study evaluated the effect of multi-frequency sonication (20 kHz, 25 kHz, 28 kHz, 40 kHz, 50 kHz) on structural characteristics of beef myofibrillar proteins (MPs) with different degrees of doneness (Rare 52~55 °C, Medium Rare 55~60 °C, Medium 60~65 °C, Medium Well 65~69 °C, Well Down 70~80 °C, and Overcooked 90 °C). The results showed that surface hydrophobicity and sulfhydryl content increased with the increase in degree of doneness. At the same degree of doneness, the sulfhydryl group contents reached the maximum at a frequency of 28 kHz. In addition, the absolute value of ζ-potential was significantly decreased after ultrasonic treatment (p < 0.05). SDS gel electrophoresis showed that the bands of beef MPs were not significantly affected by various ultrasonic frequencies, but the bands became thinner when the degree of doneness reached overcooked. Fourier transform infrared spectrum showed that with the increase of ultrasonic frequency, α-helix content decreased, and random coil content significantly increased (p < 0.05). The results of atomic force microscopy indicated that the surface structure of beef MPs was damaged, and the roughness decreased by sonication, while the roughness significantly increased when the degree of doneness changed from medium to overripe (p < 0.05). In conclusion, multi-ultrasound combined with degree of doneness treatment alters the structural characteristics of beef MPs.

Adsorption and controlled release performances of flavor compounds by rice bran insoluble dietary fiber improved through steam explosion method

In this study, steam explosion was employed as a modification process for rice bran insoluble dietary fiber (RBIDF) to improve the flavor adsorption and controlled release capacities of RBIDF. Results showed that the flavor adsorption ability of RBIDF was effectively improved due to the unfolding structure, increased specific surface area and pore volume and exposure of more functional groups after steam explosion treatment. The mechanism of the flavor adsorption behavior of modified RBIDF was preliminarily explored using adsorption kinetics and isotherms combined with SEM and DSC analysis. Results showed that the Langmuir isotherm model and pseudo-second-order kinetic model yielded the best fit to the adsorption data, indicating monolayer adsorption of flavor onto the modified RBIDF, and the adsorption was mainly driven by chemisorption process. The flavor release profile of modified RBIDF was investigated by HS-SPME/GC-MS and E-nose. After long-time storage, the flavor compounds were retained at a higher concentration in the modified RBIDF compared with the untreated RBIDF, indicating that the steam explosion treatment prolonged the retention time and enhanced the retention and controlled release capacities of RBIDF for flavor compounds. This study provides indications for potential applications of steam explosion-modified RBIDF as a novel flavor delivery system and functional ingredient.

Comprehensive Multi-Spectroscopy and Molecular Docking Understanding of Interactions between Fermentation-Stinky Compounds and Mandarin Fish Myofibrillar Proteins

The release of flavor compounds is a critical factor that influences the quality of fermented foods. A recent study investigated the interactions between four fermentation-stinky compounds (indole, isovaleric acid, dimethyl disulfide, and dibutyl phthalate) and myofibrillar proteins (MPs). The results indicated that all four fermentation-stinky compounds had different degrees of binding to MPs, with dibutyl phthalate and dimethyl disulfide exhibiting stronger interactions. Reduced hydrophobicity enhanced these interactions. Multi-spectroscopy showed that static fluorescence quenching was dominant in the MPs-fermentation-stinky compound complexes. The interaction altered the secondary structure of MPs, predominantly transitioning from β-sheets to α-helix or random coil structures via hydrogen bond interactions. Molecular docking confirmed that these complexes maintained steady states due to stronger hydrogen bonds, van der Waals forces, ionic bonds, conjugate systems, and lower hydrophobicity interactions. Hence, it is a novel sight that the addition of hydrophobic bond-disrupting agents could improve the flavor of fermented foods.

Contribution of process-induced molten-globule state formation in duck liver protein to the enhanced binding ability of (E,E)-2,4-heptadienal

BACKGROUND

Extracted proteins of alternative animal origin tend to present strong off-flavor perception due to physicochemical interactions of coextracted off-flavor compounds with proteins. To investigate the relationship between absorption behaviors of volatile aromas and the processes-induced variations in protein microstructures and molecular conformations, duck liver protein isolate (DLp) was subjected to heating (65/100 °C, 15 min) and ultra-high pressure (UHP, 100-500 MPa/10 min, 28 °C) treatments to obtain differential unfolded protein states.

RESULTS

Heat and UHP treatments induced the unfolding of DLp to varied degrees, as revealed by fluorescence spectroscopy, ultraviolet-visible absorption, circular dichroism spectra and surface hydrophobicity measurements. Two types of heating-denatured states with varied unfolding degrees were obtained, while UHP at both levels of 100/500 MPa caused partial unfolding of DLp and the presence of a molten-globule state, which significantly enhanced the binding affinity between DLp and (E,E)-2,4-heptadienal. In particular, significantly modified secondary structures of DLp were observed in heating-denatured samples. Excessive denaturing and unfolding degrees resulted in no significant changes in the absorption behavior of the volatile ligand, as characterized by observations of fluorescence quenching and analysis of headspace concentrations.

CONCLUSION

Defining process-induced conformational transition behavior of matrix proteins could be a promising strategy to regulate food flavor attributes and, particularly, to produce DLp coextracted with limited off-flavor components by modifying their interaction during extraction processes. © 2023 Society of Chemical Industry.

Microwave processing technology influences the functional and structural properties of fish gelatin

The objective of this study was to evaluate the effects of microwave processing technology (MPT, 240-800 W, 1 and 4 min) on the functional and structural properties of fish gelatin (FG). It showed that MPT could increase gel strength and texture properties of FG, especially for 240 W. MPT greatly increased emulsifying activity index (EAI) of FG, but decreased its emulsion stability index (ESI). Rheology results showed that MPT increased viscosity of FG, but decreased gelation times. Intrinsic fluorescence and Fourier transform infrared (FTIR) spectroscopy results indicated that MPT could unfold gelatin, contributing to the formation of H-bonds. Scanning electron microscopy (SEM) analysis revealed that low power and short time of MPT-treated gelatin gels had much more dense and less voids. This work provided guidance for the applications of MPT to improve the functional properties of FG, and the results show that MPT-treated FG can replace mammalian gelatin and meet the religious requirement.

Physicochemical, structural, functional and flavor adsorption properties of white shrimp (Penaeus vannamei) proteins as affected by processing methods

Proteins contribute to the flavor release and texture of foods besides their nutritional attributes. However, processing affects the protein structural conformation and, thus, their functional properties. White shrimp proteins (WSP) are well known for their nutritional and functional properties and limited attention has been paid to the flavor adsorption properties of WSP. This study investigated the effects of processing methods such as microwave drying, hot air drying, roasting, and boiling on the structural (secondary and tertiary) changes and physicochemical, functional, and flavor adsorption properties of white shrimp proteins (WSP). Structural changes of WSPs were evaluated by Fourier Transform Infrared (FTIR) spectroscopy, fluorescence spectroscopy, and sulfhydryl bond content. Results revealed that the processing triggered structural changes that affected the functional properties of WSP. The highest surface hydrophobicity (H₀) of WSP in boiling (58.27 ± 1.68) and microwave drying (39.83 ± 0.83) caused increased emulsifying properties and decreased water solubility. The increased content of α-helix and random coils leads to cross-linking and protein aggregation in hot air drying (21.62 ± 0.37 %) and roasting (24.30 ± 0.24 %), which leads to low H₀ and high foaming properties. Processing has increased the flavor adsorption ability of WSP. Among all the processing methods, boiling has shown the highest flavor adsorption potential, followed by microwave drying. The findings broaden the scope of techno-functional properties of WSP in the food industry by thermal treatment modification.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

Evaluation of key aroma compounds and protein secondary structure in the roasted Tan mutton during the traditional charcoal process

The traditional charcoal technique was used to determine the changes in the key aroma compounds of Tan mutton during the roasting process. The results showed that the samples at the different roasting time were distinguished using GC-MS in combination with PLS-DA. A total of 26 volatile compounds were identified, among which 14 compounds, including (E)-2-octenal, 1-heptanol, hexanal, 1-hexanol, heptanal, 1-octen-3-ol, 1-pentanol, (E)-2-nonenal, octanal, 2-undecenal, nonanal, pentanal, 2-pentylfuran and 2-methypyrazine, were confirmed as key aroma compounds through the odor activity values (OAV) and aroma recombination experiments. The OAV and contribution rate of the 14 key aroma compounds were maintained at high levels, and nonanal had the highest OAV (322.34) and contribution rate (27.74%) in the samples after roasting for 10 min. The content of α-helix significantly decreased (P < 0.05), while the β-sheet content significantly increased (P < 0.05) during the roasting process. The content of random coils significantly increased in the samples roasted for 0-8 min (P < 0.05), and then no obvious change was observed. At the same time, β-turn content had no obvious change. Correlation analysis showed that the 14 key aroma compounds were all positively correlated with the content of α-helix and negatively correlated with the contents of β-sheet and random coil, and also positively correlated with the content of β-turn, except hexanal and 2-methypyrazine. The results are helpful to promoting the industrialization of roasted Tan mutton.

Insight into the incredible effects of microwave heating: Driving changes in the structure, properties and functions of macromolecular nutrients in novel food

Microwave heating technology performs the characteristics of fast heating, high efficiency, green energy saving and easy control, which makes it deeply penetrate into the food industry and home cooking. It has the potential to alter the appearance and flavor of food, enhance nutrient absorption, and speed up the transformation of active components, which provides an opportunity for the development of innovation foods. However, the change of food driven by microwave heating are very complex, which often occurs beyond people's cognition and blocks the development of new food. It is thus necessary to explore the transformation mechanism and influence factors from the perspectives of microwave technology and food nutrient diversity. This manuscript focuses on the nutritional macromolecules in food, such as starch, lipid and protein, and systematically analyzes the change rule of structure, properties and function under microwave heating. Then, the flavor, health benefits, potential safety risks and bidirectional allergenicity associated with microwave heating are fully discussed. In addition, the development of new functional foods for health needs and future market based on microwave technology is also prospected. It aims to break the scientific fog of microwave technology and provide theoretical support for food science to understand the change law, control the change process and use the change results.

Evaluation of the adsorption capacity and mechanism of soy protein isolate for volatile flavor compounds: Role of different oxygen-containing functional groups

Mechanism of soy protein isolate (SPI) adsorbing isomers of volatile flavor compounds (VFCs: 2-octanone, 1-octen-3-ol and octanal) were investigated by exploring the interaction between different oxygen-containing functional groups (OCF groups: carbonyl, alcohol hydroxyl and aldehyde group) and SPI in this study. VFCs made SPI aggregate into larger particle size, and an increase in β-sheet and β-turn was observed. Octanal has strongest binding capacity to SPI, followed by 1-octen-3-ol and 2-octanone. Fluorescence analysis revealed that static quenching occurred between the VFCs and SPI, which suggested that SPI-VFCs complex were formed. Double logarithmic Stern-Volmer indicated the strongest interaction between aldehyde group and SPI, which was proved by surface plasmon resonance. Finally, molecular docking results showed more hydrogen bonds between octanal and SPI. The results showed that aldehyde groups were more likely to interact with SPI than others, probably due to their tendency to form more hydrogen bonds.

Influence of Proteolysis on the Binding Capacity of Flavor Compounds to Myofibrillar Proteins

Proteolysis occurs extensively during postmortem aging, enzymatic tenderization and fermentation of meat products, whereas less is understood regarding how proteolysis affects meat flavor. Myofibrillar proteins (MP) were extracted from beef longissimus dorsi muscle and subsequently treated with three commercial proteases. The effect of proteolysis on the interactions between the treated MP and butyraldehyde, 2-pentanone, octanal and 2-octanone was investigated. The progress of proteolysis increased the degree of hydrolysis (DH) and the surface hydrophobicity but decreased the turbidity and particle size. Fluorescence-quenching analysis results indicated that the enzymatic treatment generally increased the quenching constant (Ksv) between the treated MP and ketones but decreased the Ksv between the treated MP and aldehydes, and the papain treatment changed the Ksv value to a larger degree than treatment with proteinase K and bromelain. The adsorption assay showed that the proteinase K treatment largely increased the adsorption capacity of the MP to octanal (by 15.8−19.3%), whereas the bromelain treatment significantly reduced the adsorption capacity of the treated MP to butyraldehyde (by 6.0−7.9%) and 2-pentanone (by 9.7−11.9%). A correlation analysis demonstrated a strong positive correlation (0.859, p < 0.05) between the DH of the MP and the adsorption ability of the treated MP to octanal. This study highlighted the significant but complex influence of proteolysis on MP binding capacity to flavor compounds.

Ultrasound treatment enhanced the ability of the porcine myofibrillar protein to bind furan compounds: Investigation of underlying mechanisms

This study was designed to explore the effects of different ultrasound power levels (0-600 W) on the ability of myofibrillar protein (MP) to bind furan compounds by analyzing the results of SDS-PAGE, particle size, Raman spectra, fluorescence intensity, solubility, turbidity, zeta potential, surface hydrophobicity, sulfhydryl content, solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). As ultrasound power levels were increased from 0 to 500 W, the hydrophobic bonding sites, hydrogen-bonding sites, and electrostatic effects increased due to the unfolding and depolymerization of MP, thus enhancing the ability of MP to bind furan (flavor-enhancing) compounds. Consistent with these results, the positive effect of ultrasound resulted in ability of MP to bind furan compounds increased by 19.00 % to 33.32 %. However, after 600-W ultrasound treatment, the MP aggregated again and the bonding sites were re-embedded, which decreased the furan-binding ability.

Effect of processing technologies on the digestibility of egg proteins

Egg and egg products are a rich source of highly bioavailable animal proteins. Several processing technologies can affect the structural and functional properties of these proteins differently and can influence their fate inside the gastrointestinal tract. The present review examines some of the processing technologies for improving egg protein digestibility and discusses how different processing conditions affect the digestibility of egg proteins under gastrointestinal digestion environments. To provide up-to-date information, most of the studies included in this review have been published in the last 5 years on different aspects of egg protein digestibility. Digestibility of egg proteins can be improved by employing some processing technologies that are able to improve the susceptibility of egg proteins to gastrointestinal proteases. Processing technologies, such as pulsed electric field, high-pressure, and ultrasound, can induce conformational and microstructural changes that lead to unfolding of the polypeptides and expose active sites for further interactions. These changes can enhance the accessibility of digestive proteases to cleavage sites. Some of these technologies may inactivate some egg proteins that are enzyme inhibitors, such as trypsin inhibitors. The underlying mechanisms of how different technologies mediate the egg protein digestibility have been discussed in detail. The proteolysis patterns and digestibility of the processed egg proteins are not always predictable and depends on the processing conditions. Empirical input is required to tailor the optimization of processing conditions for favorable effects on protein digestibility.

Capacity of myofibrillar protein to adsorb characteristic fishy-odor compounds: Effects of concentration, temperature, ionic strength, pH and yeast glucan addition

The capacity of myofibrillar protein (MP) to adsorb fishy-odors (hexanal, nonanal, 1-octen-3-ol) was investigated under the influences of concentration, temperature, pH, ionic strength and yeast glucan (YG) addition. The adsorption of MP for fishy-odors was in the order of nonanal > hexanal > 1-octen-3-ol. With increasing MP concentration, the binding of protein-aldehydes was facilitated, in contrast to a decrease trend in binding to 1-octen-3-ol. Meanwhile, MP adsorption capacity for off-odors peaked at 40 °C. Additionally, low ionic strength (0.2 mol/L) could promote MP adsorption for off-odors, while high ionic strength (0.6-1.0 mol/L) could reduce its adsorption for hexanal and 1-octen-3-ol. Moreover, MP had higher adsorption capacity under extreme pH values (pH 3 and 11). Furthermore, YG was shown as an ideal additive to adsorb off-odors due to its large specific surface area and good stability. This work provides useful information on how to deodorize fishy-odors in fish products.