Influence of phenolic compounds on the structural characteristics, functional properties and antioxidant activities of Alcalase-hydrolyzed protein isolate from Cinnamomum camphora seed kernel

A Polyphenol Decorated Triplex Hybrid Biomaterial: Structure-Function, Release Profiles, Sorption, and Antipathogenic Effects

Herein, nonwoven alkali modified flax substrates were coated with incremental levels of chitosan, followed by immobilization of tannic acid, via a facile "dip-coating" strategy to yield a unique hierarchal "triplex" hybrid biomaterial, denoted as "THB". The characterization of the physicochemical properties of THB employed complementary spectroscopic (IR, Raman, and NMR) techniques, which support the role of hydrogen bonding and electrostatic interactions between the components: chitosan as the secondary biopolymer coating and the tertiary adsorbed polyphenols. XRD and SEM techniques provide further structural insight that confirms the unique semicrystalline nature and porous hierarchal structure of the biocomposite. The THBs present a polyphenol kinetic release profile that follows the Korsmeyer-Peppas model that concurs with Fickian diffusion for heterogeneous polymer systems. Furthermore, these systems demonstrate a tailored solvent uptake capacity (up to 4 g/g) in aqueous PBS media. Antipathogenic activity tests revealed 95% elimination of pathogens (E. coli, S. aureus, and C. albicans) at a dose of 50 mg for the THB system. The trend in the structure-property relationships for the THB systems indicates synergistic effects of electrostatic multiform interactions between protonated chitosan and the polyphenol units. Herein, we report the first example of a unique hierarchal biomaterial via a facile design strategy for diversiform roles as responsive adsorbents for environmental remediation to biomedical applications (e.g., controlled release, topical administration, or antimicrobial surface coatings).

High pressure-assisted enzymatic hydrolysis potentiates the production of quinoa protein hydrolysates with antioxidant and ACE-inhibitory activities

The impact of different pressure levels in the HHP-assisted hydrolysis by Alcalase of quinoa proteins on the catalytic efficiency, peptide release, phenolic compounds content, and biological activities was investigated. The protein profile (SDS-PAGE) showed a more extensive peptide breakdown for the HHP-assisted proteolysis at 300-400 MPa, which was confirmed by the higher extent of hydrolysis and peptide concentration. Quinoa protein hydrolysates (QPH) produced at 200 and 300 MPa exhibited higher total phenolic contents and antioxidant activities (methanol-acetone and aqueous extracts) when compared to the non-hydrolyzed (QPI) and non-pressurized hydrolyzed samples. Kaempferol dirhamnosyl-galactopyranoside was the prevalent phenolic compound in those samples, increasing total flavonoids by 1.8-fold over QPI. The QPH produced at 300 MPa inhibited ACE more effectively, exhibiting the greatest anti-hypertensive potential, along with the presence of several ACE-inhibitory peptides. The peptide sequences GSHWPFGGK, FSIAWPR, and PWLNFK presented the highest Peptide Ranker scores and were predicted to have ACE inhibitory, DPP-IV inhibitory, and antioxidant activities. Mild pressure levels were effective in producing QPH with enhanced functionality due to the effects of bioactive soluble phenolics and low molecular weight peptides.

Effect of Pretreatments on the Chemical, Bioactive and Physicochemical Properties of Cinnamomum camphora Seed Kernel Extracts

Cinnamomum camphora seed kernels (CCSKs) are rich in phytochemicals, especially plant extracts. Phytochemicals play a vital role in therapy due to their strong antioxidant and anti-inflammatory activities. Extracts from CCSK can be obtained through multiple steps, including pretreatment, extraction and purification, and the purpose of pretreatment is to separate the oil from other substances in CCSKs. However, C. camphora seed kernel extracts (CKEs) were usually considered as by-products and discarded, and their potential bioactive values were underestimated. Additionally, little has been known about the effect of pretreatment on CKE. This study aimed to investigate the effects of pretreatment methods (including the solvent extraction method, cold pressing method, aqueous extraction method and sub-critical fluid extraction method) on the extraction yields, phytochemical profiles, volatile compounds and antioxidant capacities of different CKE samples. The results showed that the CKE samples were rich in phenolic compounds (15.28-20.29%) and alkaloids (24.44-27.41%). The extraction yield, bioactive substances content and in vitro antioxidant capacity of CKE pretreated by the sub-critical fluid extraction method (CKE-SCFE) were better than CKEs obtained by other methods. CKE pretreated by the solvent extraction method (CKE-SE) showed the best lipid emulsion protective capacity. Moreover, the volatile substances composition of the CKE samples was greatly influenced by the pretreatment method. The results provided a fundamental basis for evaluating the quality and nutritional value of CKE and increasing the economic value of by-products derived from CCSK.

Formation mechanism of quinoa protein hydrolysate-EGCG complexes at different pH conditions and its effect on the protein hydrolysate-lipid co-oxidation in emulsions

This study aimed to investigate the interaction, structure, antioxidant, and emulsification properties of quinoa protein hydrolysate (QPH) complexes formed with (-)-epigallocatechin gallate (EGCG) at pH 3.0 and 7.0. Additionally, the effect of pH conditions and EGCG complexation on protein hydrolysate-lipid co-oxidation in QPH emulsions was explored. The results indicated that QPH primarily interacted with EGCG through hydrophobic interactions and hydrogen bonds. This interaction led to alterations in the secondary structure of QPH, as well as a decrease in surface hydrophobicity and free SH content. Notably, the binding affinity between QPH and EGCG was observed to be higher at pH 7.0 compared to pH 3.0. Consequently, QPH-EGCG complexes exhibited more significant enhancement in antioxidant and emulsification properties at pH 7.0 than pH 3.0. The pH level also influenced the droplet size, ζ-potential, and interfacial composition of emulsions formed by QPH and QPH-EGCG complexes. Compared to QPH stabilized emulsions, QPH-EGCG stabilized emulsions were more capable of mitigating destabilization during storage and displayed fewer lipid oxidation products, carbonyl generation, and sulfhydryl groups and fluorescence loss, which implied better oxidative stability of the emulsions. Furthermore, the QPH-EGCG complexes formed at pH 7.0 exhibited better inhibition of protein hydrolysate-lipid co-oxidation. Overall, these findings provide valuable insights into the potential application of QPH and its complexes with EGCG in food processing systems.

Food-packaging applications and mechanism of polysaccharides and polyphenols in multicomponent protein complex system: A review

With the increasingly mature research on protein-based multi-component systems at home and abroad, the current research on protein-based functional systems has also become a hot spot and focus in recent years. In the functional system, the types of functional factors and their interactions with other components are usually considered to be the subjective factors of the functional strength of the system. Because this process is accompanied by the transfer of protons and electrons in the system, it has antioxidant, antibacterial and anti-inflammatory properties. Polyphenols and polysaccharides have the advantages of wide source, excellent functionality and good compatibility with proteins, and have become excellent and representative functional factors. However, polyphenols and polysaccharides are usually accompanied by poor stability, poor solubility and low bioavailability when used as functional factors. Therefore, the effect of separate release and delivery will inevitably lead to non-significant or direct degradation. After forming a multi-component composite system with the protein, the functional factor will form a stable system driven by hydrogen bonds, hydrophobic forces and electrostatic forces between the functional factor and the protein. When used as a delivery system, it will protect the functional factor, and when released, through the specific recognition of the cell membrane receptor signal, the effect of fixed-point delivery is achieved. In addition, this multi-component composite system can also form a functional composite film by other means, which has a long-term significance for prolonging the shelf life of food and carrying out specific antibacterial.

Effects of Covalent or Noncovalent Binding of Different Polyphenols to Acid-Soluble Collagen on Protein Structure, Functionality, and Digestibility

In this study, the structure, function, and digestibility of noncovalent complexes and covalent conjugates formed by acid-soluble collagen with polyphenols of different structures (quercetin, epicatechin, gallic acid, chlorogenic acid, procyanidin, and tannic acid) were investigated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that polyphenols were covalently bound to collagen by laccase catalytic oxidation. Biolayer interferometry revealed that the noncovalent binding strength of polyphenols to collagen from high to low was quercetin > gallic acid > chlorogenic acid > epicatechin, which was consistent with the trend of covalent polyphenol binding. Procyanidin and tannic acid had strong noncovalent binding, but their covalent binding ability was weak. Compared with the pure collagen, the complexes improved emulsification and antioxidant properties (more than 2.5 times), and the conjugates exhibited better thermal stability (99.4-106.8 °C) and antidigestion ability (reduced by more than 37%). The finding sheds new light on the use of collagen as a functional food ingredient in the food industry.

Geographic Pattern of Variations in Chemical Composition and Nutritional Value of Cinnamomum camphora Seed Kernels from China

Cinnamomum camphora (camphor tree) is an important non-conventional edible plant species found in East Asia. Here, a detailed characterization for the chemical composition and nutritional value of C. camphora seed kernels (CCSKs) collected from different regions in China is provided. The results showed that there were significant differences among the CCSK samples in weights (1000 fruits, 1000 seeds and 1000 kernels), proximate composition, minerals, phenolics, flavonoids and amino acid contents. The highest contents of oil (62.08%) and protein (22.17%) were found in the CCSK samples collected from Chongqing and Shanghai, respectively. The highest content of mineral in the CCSK samples was K (4345.05-7186.89 mg/kg), followed by P (2735.86-5385.36 mg/kg), Ca (1412.27-3327.37 mg/kg) and Mg (2028.65-3147.32 mg/kg). The CCSK sample collected from Guizhou had the highest levels of total phenolic and flavonoid contents (TPC and TFC), while that from Chongqing had the lowest levels. In addition, the most abundant fatty acid in the CCSK samples was capric acid (57.37-60.18%), followed by lauric acid (35.23-38.29%). Similarities in the fatty acid composition among the CCSK samples were found. The CCSK sample collected from Guizhou had the highest percentage (36.20%) of essential amino acids to total amino acids, and Chongqing had the lowest value (28.84%). These results indicated that CCSK may be developed as an excellent source of plant-based medium-chain oil, protein, dietary fiber, minerals, phytochemicals and essential amino acids.

A review of the structure, function, and application of plant-based protein-phenolic conjugates and complexes

Interactions between plant-based proteins (PP) and phenolic compounds (PC) occur naturally in many food products. Recently, special attention has been paid to the fabrication of PP-PC conjugates or complexes in model systems with a focus on their effects on their structure, functionality, and health benefits. Conjugates are held together by covalent bonds, whereas complexes are held together by noncovalent ones. This review highlights the nature of protein-phenolic interactions involving PP. The interactions of these PC with the PP in model systems are discussed, as well as their impact on the structural, functional, and health-promoting properties of PP. The PP in conjugates and complexes tend to be more unfolded than in their native state, which often improves their functional attributes. PP-PC conjugates and complexes often exhibit improved in vitro digestibility, antioxidant activity, and potential allergy-reducing activities. Consequently, they may be used as antioxidant emulsifiers, edible film additives, nanoparticles, and hydrogels in the food industry. However, studies focusing on the application of PP-PC conjugates and complexes in real foods are still scarce. Further research is therefore required to determine the structure-function relationships of PP-PC conjugates and complexes that may influence their application as functional ingredients in the food industry.

Different interactions between Tartary buckwheat protein and Tartary buckwheat phenols during extraction: Alterations in the conformation and antioxidant activity of protein

The purpose of this study is to investigate the interaction between buckwheat protein and buckwheat phenols in the process of protein extraction and to compare the effects of phenols on protein structure and antioxidant activity. With the extension of extraction time, the content of total phenol increased from 150.51 to 336.01 mg gallic acid equivalent/g sample. Four phenols and seven phenols were identified by UPLC-Q/TOF-MS as binding to proteins in non-covalent and covalent forms, respectively. The contribution of non-covalent and covalent bound phenols to the antioxidant activity of the complexes were different. Meanwhile, the binding of phenols changed the infrared characteristic peak of protein, and reduced the fluorescence intensity and surface hydrophobic value. The free amino and sulfhydryl content of the protein decreased with increasing extraction time. These findings provide valuable information for one-step preparation of protein-phenol complexes.

Structural Modification of Jackfruit Leaf Protein Concentrate by Enzymatic Hydrolysis and Their Effect on the Emulsifier Properties

Jackfruit leaf protein concentrate (LPC) was hydrolyzed by pepsin (H–Pep) and pancreatin (H–Pan) at different hydrolysis times (30–240 min). The effect of the enzyme type and hydrolysis time of the LPC on the amino acid composition, structure, and thermal properties and its relationship with the formation of O/W emulsions were investigated. The highest release of amino acids (AA) occurred at 240 min for both enzymes. H–Pan showed the greatest content of essential and hydrophobic amino acids. Low β-sheet fractions and high β-turn contents had a greater influence on the emulsifier properties. In H–Pep, the β-sheet fraction increased, while in H–Pan it decreased as a function of hydrolysis time. The temperatures of glass transition and decomposition were highest in H–Pep due to the high content of β-sheets. The stabilized emulsions with H–Pan (180 min of hydrolysis) showed homogeneous distributions and smaller particle sizes. The changes in the secondary structure and AA composition of the protein hydrolysates by the effect of enzyme type and hydrolysis time influenced the emulsifying properties. However, further research is needed to explore the use of H–Pan as an alternative to conventional emulsifiers or ingredients in functional foods.

Extraction, Isolation, and Purification of Value-Added Chemicals from Lignocellulosic Biomass

This review covers the operating conditions for extracting top value-added chemicals, such as levulinic acid, lactic acid, succinic acid, vanillic acid, 3-hydroxypropionic acid, xylitol, 2,5-furandicarboxylic acid, 5-hydroxymethyl furfural, chitosan, 2,3-butanediol, and xylo-oligosaccharides, from common lignocellulosic biomass. Operating principles of novel extraction methods, beyond pretreatments, such as Soxhlet extraction, ultrasound-assisted extraction, and enzymatic extraction, are also presented and reviewed. Post extraction, high-value biochemicals need to be isolated, which is achieved through a combination of one or more isolation and purification steps. The operating principles, as well as a review of isolation methods, such as membrane filtration and liquid–liquid extraction and purification using preparative chromatography, are also discussed.

Recent application of protein hydrolysates in food texture modification

The demand for clean labels has increased the importance of natural texture modifying ingredients. Proteins are unique compounds that can impart unique textural and structural changes in food. However, lack of solubility and extensive aggregability of proteins have increased the demand for enzymatically hydrolyzed proteins, to impart functional and structural modifications to food products. The review elaborates the recent application of various proteins, protein hydrolysates, and their role in texture modification. The impact of protein hydrolysates interaction with other food macromolecules, the effect of pretreatments, and dependence of various protein functionalities on textural and structural modification of food products with controlled enzymatic hydrolysis are explained in detail. Many researchers have acknowledged the positive effect of enzymatically hydrolyzed proteins on texture modification over natural protein. With enzymatic hydrolysis, various textural properties including foaming, gelling, emulsifying, water holding capacity have been effectively improved. It is evident that each protein is unique and imparts exceptional structural changes to different food products. Thus, selection of protein requires a fundamental understanding of its structure-substrate property relation. For wider applicability in the industrial sector, more studies on interactions at the molecular level, dosage, functionality changes, and sensorial attributes of protein hydrolysates in food systems are required.

Combined enzymatic hydrolysis and herbal extracts fortification to boost in vitro antioxidant activity of edible bird’s nest solution

Objective

Edible bird’s nest (EBN) is a popular traditional tonic food in Chinese population for centuries. Malaysia is one of the main EBN suppliers in the world. This study aims to explore the best strategy to boost the antioxidant potential of EBN solution.

Methods

In this study, the raw EBN (4%, mass to volume ratio) was initially enzymatic hydrolyzed using papain enzyme to produce EBN hydrolysate (EBNH), then spray-dried into powdered form. Next, 4% (mass to volume ratio) of EBNH powder was dissolved in ginger extract (GE), mulberry leaf extract (MLE) and cinnamon twig extract (CTE) to detect the changes of antioxidant activities, respectively.

Results

Results obtained suggest that enzymatic hydrolysis significantly reduced the viscosity of 4% EBN solution from (68.12 ± 0.69) mPa·s to (7.84 ± 0.31) mPa·s. Besides, the total phenolic content (TPC), total flavonoid content (TFC), total soluble protein, DPPH scavenging activity and ferric reducing antioxidant power (FRAP) were substantially increased following EBN hydrolysis using papain enzyme. In addition, fortification with GE, MLE and CTE had further improved the TPC, TFC, DPPH scavenging activity and FRAP of the EBNH solution. Among the samples, MLE-EBNH solution showed the most superior antioxidant potential at (86.39 ± 1.66)% of DPPH scavenging activity and (19.79 ± 2.96) mmol/L FeSO₄ of FRAP.

Conclusion

This study proved that combined enzymatic hydrolysis and MLE fortification is the best strategy to produce EBN product with prominent in vitro antioxidant potential. This preliminary study provides new insight into the compatibility of EBN with different herbal extracts for future health food production.