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Study on Physicochemical Properties of Food Protein

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Food Chemistry".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 16205

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Dr. Shudong He

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Guest Editor

School of Food Science and Biological Engineering, Hefei University of Technology, Hefei, China
Interests: food protein; food peptide; food allergy; food characteristics; food flavor; beverage development; edible film
Special Issues, Collections and Topics in MDPI journals

Dr. Wei Xu

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Guest Editor

School of Food Science and Engineering, Wuhan Polytechnic University, Wuhan, China
Interests: food protein; food peptide; food characteristics; food flavor
Special Issues, Collections and Topics in MDPI journals

Dr. Muhammad H. Aludatt

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Guest Editor

Department of Nutrition and Food Technology, Jordan University of Science and Technology, Irbid, Jordan
Interests: food chemistry and technology and their application in human nutrition (in vitro study including allergic, diabetics, hypertension and cancer)

Special Issue Information

Dear Colleagues,

With the increasing demands for nutrition and health, especially in the COVID-19 pandemic, more and more consumers are paying attention to the nutritional values of food proteins and protein-derived peptides from crops and animals. Food proteins supply adequate amounts of essential amino acids, but also contribute to the general well-being maintenance and the intervention against human diseases. Therefore, the exploitation and application of food proteins have been the primary focus of the food industry. Due to the difference in the physicochemical properties of various food proteins, such as the solubility, swelling, water retention capacity, foaming properties, gelling capacity, emulsifying and fat binding properties, it is necessary to scientifically study the quality and sensory attributes of protein foods in terms of preparation, processing, storage, and consumption. Furthermore, the physicochemical properties of proteins can be optimized by many innovative thermal and non-thermal methods including ultrasound, pH-shifting, high pressure, irradiation, glycosylation, pulsed electric field, and enzymatic modification, to improve the applicability of proteins in the food industry. Thus, more effort needs to be paid to understanding the relationship between the structure and functional properties after protein modification. Besides, the interactions of protein molecules with other food ingredients and their effects on macroscopic properties of the food systems should be considered. The Special Issue aims to publish the most advanced investigations on the physicochemical properties of food proteins and provide useful information about the structure-function relationship based on the protein modifications to explore the potential of the food proteins in food development.

Dr. Shudong He
Dr. Wei Xu
Dr. Muhammad H. Aludatt
Guest Editors

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Keywords

food protein
physicochemical properties
structure-function relationship
modification
bioactivity
food processing

Published Papers (11 papers)

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Editorial

Jump to: Research, Review

5 pages, 204 KiB

Open AccessEditorial

Study on Physicochemical Properties of Food Protein

by Shudong He

Molecules 2023, 28(24), 8145; https://doi.org/10.3390/molecules28248145 - 18 Dec 2023

Viewed by 722

Abstract

As the global population continues to grow, the demand for sustainable and nutritious food sources has never been higher [...] Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

Research

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18 pages, 3254 KiB

Open AccessArticle

Structural Characteristics and Antioxidant Mechanism of Donkey-Hide Gelatin Peptides by Molecular Dynamics Simulation

by Rong Liang, Le Xu, Chen Fan, Lele Cao and Xingfeng Guo

Molecules 2023, 28(24), 7975; https://doi.org/10.3390/molecules28247975 - 06 Dec 2023

Cited by 1 | Viewed by 857

Abstract

This study aimed to explore the structural characteristics and antioxidant mechanism of donkey-hide gelatin peptides. After hydrolysis and ultrafiltration treatment, five gelatin peptides with different molecular weights (MWs) were obtained. Amino acid analysis showed that gelatin peptides with different MWs contained a large number of amino acids, including G, P, E, N, A, and R, and differences were noted in the content of various amino acids. Fourier transform infrared spectroscopy and circular dichroism revealed that these gelatin peptides differed in terms of the peak strength of functional groups and number of secondary structures. Moreover, 26 pentapeptides/hexapeptides were identified. Among them, we investigated by molecular docking how PGPAP, which has the best antioxidant activity, may interact with the Keap1 protein. The results showed that the PGPAP-Keap1 complex had a stable conformation, and Arg415, Gly462, Phe478, and Tyr572 were the key residues involved in the binding of the peptide PGPAP to Keap1. Our results demonstrated that PGPAP could serve as a bioactive peptide with antioxidant activity. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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18 pages, 5053 KiB

Open AccessArticle

Impact of Ultrasonication on the Self-Assembly Behavior and Gel Properties of Bovine Bone Collagen I

by Hong Liu, Hongru Zhang, Kangyu Wang, Liwei Qi, Yujie Guo, Chunhui Zhang and Yang Xu

Molecules 2023, 28(7), 3096; https://doi.org/10.3390/molecules28073096 - 30 Mar 2023

Cited by 1 | Viewed by 1279

Abstract

This study deliberated the effect of ultrasonic treatment on collagen self-assembly behavior and collagen fibril gel properties. Bovine bone collagen I which had undergone ultrasonic treatment with different power (0–400 W) and duration (0–60 min) was analyzed. SDS-PAGE and spectroscopic analysis revealed that ultrasonic treatment decreased collagen molecular order degree and the number of hydrogen bonds, stretching collagen telopeptide regions while maintaining the integrity of the collagen triple-helical structure. Ultrasonic treatment (p ≤ 200 W, t ≤ 15 min) dispersed the collagen aggregates more evenly, and accelerated collagen self-assembly rate with a decreased but more homogeneous fibril diameter (82.78 ± 16.47–115.52 ± 19.51 nm) and D-periodicity lengths (62.1 ± 2.9–66.5 ± 1.8 nm) than that of the untreated collagen (119.15 ± 27.89 nm; 66.5 ± 1.8 nm). Meanwhile, ultrasonic treatment (p ≤ 200 W, t ≤ 15 min) decreased the viscoelasticity index and gel strength, enhancing thermal stability and promoting specific surface area and porosity of collagen fibril gels than that of the untreated collagen fibril gel. These results testified that collagen self-assembly behavior and collagen fibril gel properties can be regulated by ultrasonic treatment through multi-hierarchical structural alteration. This study provided a new approach for controlling in vitro collagen fibrillogenesis process so as to manufacture novel desirable collagen-based biomaterials with propitious performances for further valorization. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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17 pages, 4399 KiB

Open AccessArticle

Esterified Soy Proteins with Enhanced Antibacterial Properties for the Stabilization of Nano-Emulsions under Acidic Conditions

by Tingyu Wang, Kehan Yi, Yang Li, Huan Wang, Zhijun Fan, Hua Jin and Jing Xu

Molecules 2023, 28(7), 3078; https://doi.org/10.3390/molecules28073078 - 30 Mar 2023

Cited by 2 | Viewed by 1135

Abstract

Soy protein isolate (SPI), including β-conglycinin (7S) and glycinin (11S), generally have low solubility under weakly acidic conditions due to the pH closed to their isoelectric points (pIs), which has limited their application in acidic emulsions. Changing protein pI through modification by esterification could be a feasible way to solve this problem. This study aimed to obtain stable nano-emulsion with antibacterial properties under weakly acidic conditions by changing the pI of soy protein emulsifiers. Herein, the esterified soy protein isolate (MSPI), esterified β-conglycinin (M7S), and esterified glycinin (M11S) proteins were prepared. Then, pI, turbidimetric titration, Fourier transform infrared (FTIR) spectra, intrinsic fluorescence spectra, and emulsifying capacity of esterified protein were discussed. The droplet size, the ζ-potential, the stability, and the antibacterial properties of the esterified protein nano-emulsion were analyzed. The results revealed that the esterified proteins MSPI, M7S, and M11S had pIs, which were measured by ζ-potentials, as pH 10.4, 10.3, and 9.0, respectively, as compared to native proteins. All esterified-protein nano-emulsion samples showed a small mean particle size and good stability under weakly acidic conditions (pH 5.0), which was near the original pI of the soy protein. Moreover, the antibacterial experiments showed that the esterified protein-based nano-emulsion had an inhibitory effect on bacteria at pH 5.0. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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13 pages, 1993 KiB

Open AccessArticle

Effects of Ultra-High-Pressure Jet Processing on Casein Structure and Curdling Properties of Skimmed Bovine Milk

by Fei Xu, Lu Xue, Yanfeng Ma, Tianjiao Niu, Pei Zhao, Zijian Wu and Yanfa Wang

Molecules 2023, 28(5), 2396; https://doi.org/10.3390/molecules28052396 - 06 Mar 2023

Cited by 1 | Viewed by 1708

Abstract

Ultra-high-pressure jet processing (UHPJ) is a new non-thermal processing technique that can be employed for the homogenization and the sterilization of dairy products. However, the effects on dairy products are unknown when using UHPJ for homogenization and sterilization. Thus, this study aimed to investigate the effects of UHPJ on the sensory and curdling properties of skimmed milk and the casein structure in skimmed milk. Skimmed bovine milk was treated with UHPJ using different pressures (100, 150, 200, 250, 300 MPa) and casein was extracted by isoelectric precipitation. Subsequently, the average particle size, Zeta potential, contents of free sulfhydryl and disulfide bonds, secondary structure, and surface micromorphology were all used as evaluation indicators to explore the effects of UHPJ on the structure of casein. The results showed that with an increase of pressure, the free sulfhydryl group content changed irregularly, while the disulfide bond content increased from 1.085 to 3.0944 μmol/g. The content of α-helix and random coil in the casein decreased, while the β-sheet content increased at 100, 150, 200 MPa pressure. However, treatment with higher pressures of 250 and 300 MPa had the opposite effect. The average particle size of the casein micelles first decreased to 167.47 nm and then increased up to 174.63 nm; the absolute value of Zeta potential decreased from 28.33 to 23.77 mV. Scanning electron microscopy analysis revealed that the casein micelles had fractured into flat, loose, porous structures under pressure instead of into large clusters. After being ultra-high-pressure jet-processed, the sensory properties of skimmed milk and its fermented curd were analyzed concurrently. The results demonstrated that UHPJ could alter the viscosity and color of skimmed milk, shortening curdling time from 4.5 h to 2.67 h, and that the texture of the curd fermented with this skimmed milk could be improved to varying degrees by changing the structure of casein. Thus, UHPJ has a promising application in the manufacture of fermented milk due to its ability to enhance the curdling efficiency of skimmed milk and improve the texture of fermented milk. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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14 pages, 1519 KiB

Open AccessArticle

Identification and Structure of Epitopes on Cashew Allergens Ana o 2 and Ana o 3 Using Phage Display

by Ailin Zhang, HuiJuan Zhao, Shaohan Pei, Yue Chi, Xiuhua Fan and Jianqing Liu

Molecules 2023, 28(4), 1880; https://doi.org/10.3390/molecules28041880 - 16 Feb 2023

Cited by 1 | Viewed by 1401

Abstract

Background: Cashew (Anacardium occidentale L.) is a commercially important plant. Cashew nuts are a popular food source that belong to the tree nut family. Tree nuts are one of the eight major food allergens identified by the Food and Drug Administration in the USA. Allergies to cashew nuts cause severe and systemic immune reactions. Tree nut allergies are frequently fatal and are becoming more common. Aim: We aimed to identify the key allergenic epitopes of cashew nut proteins by correlating the phage display epitope prediction results with bioinformatics analysis. Design: We predicted and experimentally confirmed cashew nut allergen antigenic peptides, which we named Ana o 2 (cupin superfamily) and Ana o 3 (prolamin superfamily). The Ana o 2 and Ana o 3 epitopes were predicted using DNAstar and PyMoL (incorporated in the Swiss-model package). The predicted weak and strong epitopes were synthesized as peptides. The related phage library was built. The peptides were also tested using phage display technology. The expressed antigens were tested and confirmed using microtiter plates coated with pooled human sera from patients with cashew nut allergies or healthy controls. Results: The Ana o 2 epitopes were represented by four linear peptides, with the epitopes corresponding to amino acids 108–111, 113–119, 181–186, and 218–224. Furthermore, the identified Ana o 3 epitopes corresponding to amino acids 10–24, 13–27, 39–49, 66–70, 101–106, 107–114, and 115–122 were also screened out and chosen as the key allergenic epitopes. Discussion: The Ana o 3 epitopes accounted for more than 40% of the total amino acid sequence of the protein; thus, Ana o 3 is potentially more allergenic than Ana o 2. Conclusions: The bioinformatic epitope prediction produced subpar results in this study. Furthermore, the phage display method was extremely effective in identifying the allergenic epitopes of cashew nut proteins. The key allergenic epitopes were chosen, providing important information for the study of cashew nut allergens. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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17 pages, 2880 KiB

Open AccessArticle

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate

by Zhiguo Na, Haixin Bi, Yingbin Wang, Yujuan Guo and Yongqiang Ma

Molecules 2023, 28(2), 643; https://doi.org/10.3390/molecules28020643 - 08 Jan 2023

Cited by 3 | Viewed by 1339

Abstract

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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15 pages, 1373 KiB

Open AccessArticle

Ultrasound-Assisted Preparation of Maillard Reaction Products Derived from Hydrolyzed Soybean Meal with Meaty Flavor in an Oil-In-Water System

by Yongkang Ye, Shengquan Dai, Hongyan Zhang, Shudong He, Wanwan Hu, Xiaodong Cao and Zhaojun Wei

Molecules 2022, 27(21), 7236; https://doi.org/10.3390/molecules27217236 - 25 Oct 2022

Cited by 2 | Viewed by 1306

Abstract

In the present work, we prepared Maillard reaction products (MRPs) derived from enzyme hydrolyzed soybean meal with ultrasound assistance in an oil-(oxidized lard)-in-water system (UEL-MRPs) or oil-free system (UN-MRPs), and the effect of ultrasound on the properties of the obtained MRPs was evaluated. The analysis of fatty acids in lard with different treatments showed that ultrasound can generate more unsaturated fatty acids in the aqueous phase. The UV–Vis absorbances of UEL-MRPs, UN-MRPs, and MRPs obtained in an oil-in-water system (EL-MRPs) and MRPs obtained in an oil-free system (N-MRPs) at 294 and 420 nm indicated that ultrasound could increase the amount of Maillard reaction intermediates and melanoids in the final products of the Maillard reaction. This was in line with the result obtained from color change determination—that ultrasound can darken the resultant MRPs. Volatile analysis showed ultrasound can not only increase the number of volatile substances, but also greatly increase the composition of volatile substances in UEL-MRPs and UN-MRPs, especially the composition of those contributing to the flavor of the MRPs, such as oxygen-containing heterocycles, sulfur-containing compounds, and nitrogen-containing heterocycles. Descriptive sensory evaluation revealed that UN-MRPs and UEL-MRPs had the highest scores in total acceptance, ranking in the top two, and UEL-MRPs had the strongest meaty flavor among these four kinds of MRPs. Furthermore, the measurements of antioxidant activities, including DPPH radical-scavenging activity, hydroxyl radical scavenging ability, and ferric ion reducing antioxidant power, were conducted, showing that UN-MRPs exhibited the highest antioxidant activity among all the MRPs. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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13 pages, 2169 KiB

Open AccessArticle

Fabrication and Characterization of the Egg-White Protein Chitosan Double-Layer Emulsion

by Qingmei Pan, Zhipeng Zhang, Ruifang Wu, Danjun Guo, Wei Xu, Hongxun Wang and Yang Yi

Molecules 2022, 27(18), 6036; https://doi.org/10.3390/molecules27186036 - 16 Sep 2022

Cited by 1 | Viewed by 1457

Abstract

Egg-white protein has an abundance of hydrophobic amino acids and could be a potential emulsifier after modification. Here, egg-white protein was modified via ultrasonic and transglutaminase treatments to destroy the globular structure. The egg-white protein gel particles (EWP-GPs) were prepared and then a novel highly stable EWP-chitosan double-layer emulsion was constructed. When ultrasonic treatment was applied at 240 W and TGase (20 U/g EWP) treatment, the EWP-GPs had a low particle size and good emulsification performance. The particle size of EWP-GPs was a minimum of 287 nm, and the polymer dispersity index (PDI) was 0.41. The three-phase contact angle (θ_o/w) of EWP-GPs was 79.6° (lower than 90°), performing with good wettability. Based on these results, the EWP-chitosan double-layer emulsion was prepared through the EWP-GPs being treated with 240 W ultrasound, TGase, and chitosan in this study. When the double-layer emulsion had 0.6% (v/v) chitosan, the zeta potential of the double-layer emulsion was −1.1 mV and the double-layer emulsion had a small particle size (56.87 µm). The creaming index of double-layer emulsion at 0.6% (v/v) chitosan was 16.3% and the droplets were dispersed uniformly. According to the rheological results, the storage modulus (G′) was larger than the loss modulus (G″) in the whole frequency, indicating the formation of an elastic gel network structure in the emulsion. It is hoped to develop a novel food-grade stabilizer and a stable double-layer emulsion, providing new environment-friendly processing in hen egg products and delivery systems. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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10 pages, 2827 KiB

Open AccessArticle

Effects of Different Denaturants on the Properties of a Hot-Pressed Peanut Meal-Based Adhesive

by Yang Qu, Qin Guo, Tian Li, Hongzhi Liu and Qiang Wang

Molecules 2022, 27(15), 4878; https://doi.org/10.3390/molecules27154878 - 30 Jul 2022

Cited by 4 | Viewed by 1248

Abstract

Plant protein-based adhesives could fundamentally solve the problem of formaldehyde-based adhesive releasing formaldehyde, but enhancing bonding strength and water resistance is a necessary measure to realize practical applications. In this study, the effects of different denaturants on the properties of a hot-pressed peanut meal (HPM)-based adhesive before and after crosslinking were studied. Papain, sodium dodecyl sulfate (SDS), urea and crosslinker-polyamide epichlorohydrin (PAE) were used to prepare HPM-based adhesives. The functional groups, bonding strength, thermal behaviors, mass loss, moisture uptake value, viscosity and fracture surface of adhesive samples were analyzed. As a result, (1) papain was used to break HPM protein (HPMP) into polypeptide chains and to reduce the water resistance. (2) SDS and urea unfold the HPMP molecule and expose internal hydrophobic groups to improve the water resistance of the adhesive. (3) A denser network structure was formed by PAE and HPMP molecules, which significantly improved the bonding strength and water resistance of adhesives. In particular, after SDS denaturation and PAE crosslinking, compared with pure HPM adhesive, the wet shear strength increased by 96.4%, the mass loss and moisture uptake value reduced by 41.4% and 69.4%, and viscosity increased by 30.4%. This work provided an essential guide to design and prepare HPM-based adhesives. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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16 pages, 2806 KiB

Open AccessReview

Modification and Solubility Enhancement of Rice Protein and Its Application in Food Processing: A Review

by Jingjing Yang, Dan Meng, Zijian Wu, Jinyu Chen and Lu Xue

Molecules 2023, 28(10), 4078; https://doi.org/10.3390/molecules28104078 - 13 May 2023

Cited by 2 | Viewed by 2147

Abstract

Rice protein is a high-quality plant-based protein source that is gluten-free, with high biological value and low allergenicity. However, the low solubility of rice protein not only affects its functional properties such as emulsification, gelling, and water-holding capacity but also greatly limits its applications in the food industry. Therefore, it is crucial to modify and improve the solubility of rice protein. In summary, this article discusses the underlying causes of the low solubility of rice protein, including the presence of high contents of hydrophobic amino acid residues, disulfide bonds, and intermolecular hydrogen bonds. Additionally, it covers the shortcomings of traditional modification methods and the latest compound improvement methods, compares various modification methods, and puts forward the best sustainable, economical, and environmentally friendly method. Finally, this article lists the uses of modified rice protein in dairy, meat, and baked goods, providing a reference for the extensive application of rice protein in the food industry. Full article

(This article belongs to the Special Issue Study on Physicochemical Properties of Food Protein)

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