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Chemical and Functional Properties of Food Proteins

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

Deadline for manuscript submissions: closed (7 January 2022) | Viewed by 20143

Special Issue Editors

Department of Food, Environmental and Nutritional Sciences, University of Milan, DISMA, Via G Celoria 2, I-20133 Milan, Italy
Interests: food proteins; food enzymes; iron metabolism; cofactor assembly;
Department of Food, Environmental and Nutritional Sciences, University of Milan, DISMA, Via G Celoria 2, I-20133 Milan, Italy
Interests: food allergens; structural investigation methodologies
Department of Agriculture, University of Naples Federico II, Via Univ 100, I-80055 Portici, NA, Italy
Interests: “omics” for food proteins, their derivatives, and their breakdown products

Special Issue Information

Dear Colleagues,

Proteins play a relevant role in foods not only as a source of amino acids or as modulators of the bioavailability of countless micronutrients, but also in terms of their contribution to the hedonistic properties of almost all foods, of food shelf-life, and as a source of bioactives. The possibility of modifying various levels of their structure through physical, chemical, or enzymatic intervention makes proteins the most versatile component in any food. This Special Issue will address how the structural features of food protein relate to properties that are of interest to the food technologist, the nutritionist, and the consumer. Focus will be placed on the molecular determinants of the chemical and structural modifications of food proteins ensuing from traditional and innovative processes, taking into account also the interplay among proteins and other food components, and innovative protein sources. The Special Issue will also provide an update on the various methodologies that may be used to assess the nature, the kinetics, and the practical impact of these modifications.

Perspective topics include (but are not limited to):

  • How to get the right protein (and how to handle it): structure–functionality relationships in food proteins;
  • The interplay between proteins and non-protein food components;
  • Process-induced covalent modification of food proteins: at the crossroads of chemistry and technology;
  • Relevance of “omics” approaches to food-protein studies;
  • Before during, and after: digestibility, bioaccessibility and protein-derived bioactives;
  • Addressing methodological challenges;
  • Novel sources of food proteins;
  • Assessing the risk/benefit balance.

Prof. Dr. Francesco Bonomi
Guest Editor

Prof. Dr. Stefania Iametti
Prof. Pasquale Ferranti
Co-Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • food proteins
  • process-related modifications
  • food allergens
  • food bioactives
  • bioavailability
  • novel food proteins

Published Papers (8 papers)

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Research

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14 pages, 680 KiB  
Article
Quantification of Protein “Biomarkers” in Wheat-Based Food Systems: Dealing with Process-Related Issues
by Mauro Marengo, Aristodemo Carpen, Gianfranco Mamone, Pasquale Ferranti and Stefania Iametti
Molecules 2022, 27(9), 2637; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27092637 - 20 Apr 2022
Cited by 1 | Viewed by 1179
Abstract
Selected food proteins may represent suitable markers for assessing either the presence/absence of specific food ingredients or the type and intensity of food processes. A fundamental step in the quantification of any protein marker is choosing a proper protocol for solubilizing the protein [...] Read more.
Selected food proteins may represent suitable markers for assessing either the presence/absence of specific food ingredients or the type and intensity of food processes. A fundamental step in the quantification of any protein marker is choosing a proper protocol for solubilizing the protein of interest. This step is particularly critical in the case of solid foods and when the protein analyte is prone to undergo intermolecular disulfide exchange reactions with itself or with other protein components in the system as a consequence of process-induced unfolding. In this frame, gluten-based systems represent matrices where a protein network is present and the biomarker proteins may be either linked to other components of the network or trapped into the network itself. The protein biomarkers considered here were wheat gluten toxic sequences for coeliac (QQPFP, R5), wheat germ agglutinin (WGA), and chicken egg ovalbumin (OVA). These proteins were considered here in the frame of three different cases dealing with processes different in nature and severity. Results from individual cases are commented as for: (1) the molecular basis of the observed behavior of the protein; (2) the design of procedure aimed at improving the recovery of the protein biomarker in a form suitable for reliable identification and quantification; (3) a critical analysis of the difficulties associated with the plain transfer of an analytical protocol from one product/process to another. Proper respect for the indications provided by the studies exemplified in this study may prevent coarse errors in assays and vane attempts at estimating the efficacy of a given treatment under a given set of conditions. The cases presented here also indicate that recovery of a protein analyte often does not depend in a linear fashion on the intensity of the applied treatment, so that caution must be exerted when attributing predictive value to the results of a particular study. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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16 pages, 2298 KiB  
Article
Hydrophobicity Enhances the Formation of Protein-Stabilized Foams
by Roy J. B. M. Delahaije and Peter A. Wierenga
Molecules 2022, 27(7), 2358; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27072358 - 06 Apr 2022
Cited by 6 | Viewed by 1959
Abstract
Screening proteins for their potential use in foam applications is very laborious and time consuming. It would be beneficial if the foam properties could be predicted based on their molecular properties, but this is currently not possible. For protein-stabilized emulsions, a model was [...] Read more.
Screening proteins for their potential use in foam applications is very laborious and time consuming. It would be beneficial if the foam properties could be predicted based on their molecular properties, but this is currently not possible. For protein-stabilized emulsions, a model was recently introduced to predict the emulsion properties from the protein molecular properties. Since the fundamental mechanisms for foam and emulsion formation are very similar, it is of interest to determine whether the link to molecular properties defined in that model is also applicable to foams. This study aims to link the exposed hydrophobicity with the foam ability and foam stability, using lysozyme variants with altered hydrophobicity, obtained from controlled heat treatment (77 °C for 0–120 min). To establish this link, the molecular characteristics, interfacial properties, and foam ability and stability (at different concentrations) were analysed. The increasing hydrophobicity resulted in an increased adsorption rate constant, and for concentrations in the protein-poor regime, the increasing hydrophobicity enhanced foam ability (i.e., interfacial area created). At higher relative exposed hydrophobicity (i.e., ~2–5 times higher than native lysozyme), the adsorption rate constant and foam ability became independent of hydrophobicity. The foam stability (i.e., foam collapse) was affected by the initial foam structure. In the protein-rich regime—with nearly identical foam structure—the hydrophobicity did not affect the foam stability. The link between exposed hydrophobicity and foam ability confirms the similarity between protein-stabilized foams and emulsions, and thereby indicates that the model proposed for emulsions can be used to predict foam properties in the future. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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16 pages, 2099 KiB  
Article
Tritordeum as an Innovative Alternative to Wheat: A Comparative Digestion Study on Bread
by Chiara Nitride, Giovanni D’Auria, Andrea Dente, Viola Landolfi, Gianluca Picariello, Gianfranco Mamone, Massimo Blandino, Raffaele Romano and Pasquale Ferranti
Molecules 2022, 27(4), 1308; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27041308 - 15 Feb 2022
Cited by 4 | Viewed by 2168
Abstract
Tritordeum results from the crossbreeding of a wild barley (Hordeum chilense) species with durum wheat (Triticum turgidum spp. turgidum). This hexaploid crop exhibits agronomic and rheological characteristics like soft wheat, resulting in an innovative raw material to produce baked [...] Read more.
Tritordeum results from the crossbreeding of a wild barley (Hordeum chilense) species with durum wheat (Triticum turgidum spp. turgidum). This hexaploid crop exhibits agronomic and rheological characteristics like soft wheat, resulting in an innovative raw material to produce baked goods. We applied a gel-based proteomic approach on refined flours to evaluate protein expression differences among two widespread tritordeum cultivars (Aucan and Bulel) taking as the reference semolina and flour derived from a durum and a soft wheat cvs, respectively. The products of in vitro digestion of model breads were analyzed to compare bio-accessibility of nutrients and mapping tritordeum bread resistant peptides. Significant differences among the protein profiles of the four flours were highlighted by electrophoresis. The amino acid bio-accessibility and the reducing sugars of tritordeum and wheat breads were comparable. Tritordeum cvs had about 15% higher alpha-amino nitrogen released at the end of the duodenal simulated digestion than soft wheat (p < 0.05). Bulel tritordeum flour, bread and digested bread had about 55% less R5-epitopes compared to the soft wheat. Differences in protein expression found between the two tritordeum cvs reflected in diverse digestion products and allergenic and celiacogenic potential of the duodenal peptides. Proteomic studies of a larger number of tritordeum cvs may be successful in selecting those with good agronomical performances and nutritional advantages. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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15 pages, 1094 KiB  
Article
Impact of Thermal Treatment on the Starch-Protein Interplay in Red Lentils: Connecting Molecular Features and Rheological Properties
by Andrea Bresciani, Davide Emide, Francesca Saitta, Dimitrios Fessas, Stefania Iametti, Alberto Barbiroli and Alessandra Marti
Molecules 2022, 27(4), 1266; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27041266 - 14 Feb 2022
Cited by 10 | Viewed by 2155
Abstract
Thermal treatments are widely applied to gluten-free (GF) flours to change their functionality. Despite the interest in using pulses in GF formulations, the effects of thermal treatment at the molecular level and their relationship with dough rheology have not been fully addressed. Raw [...] Read more.
Thermal treatments are widely applied to gluten-free (GF) flours to change their functionality. Despite the interest in using pulses in GF formulations, the effects of thermal treatment at the molecular level and their relationship with dough rheology have not been fully addressed. Raw and heat-treated red lentils were tested for starch and protein features. Interactions with water were assessed by thermogravimetric analysis and water-holding capacity. Finally, mixing properties were investigated. The thermal treatment of red lentils induced a structural modification of both starch and proteins. In the case of starch, such changes consequently affected the kinetics of gelatinization. Flour treatment increased the temperature required for gelatinization, and led to an increased viscosity during both gelatinization and retrogradation. Regarding proteins, heat treatment promoted the formation of aggregates, mainly stabilized by hydrophobic interactions between (partially) unfolded proteins. Overall, the structural modifications of starch and proteins enhanced the hydration properties of the dough, resulting in increased consistency during mixing. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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19 pages, 1721 KiB  
Article
Physicochemical and Functional Properties of 2S, 7S, and 11S Enriched Hemp Seed Protein Fractions
by Comfort F. Ajibola and Rotimi E. Aluko
Molecules 2022, 27(3), 1059; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27031059 - 04 Feb 2022
Cited by 13 | Viewed by 2405
Abstract
The hemp seed contains protein fractions that could serve as useful ingredients for food product development. However, utilization of hemp seed protein fractions in the food industry can only be successful if there is sufficient information on their levels and functional properties. Therefore, [...] Read more.
The hemp seed contains protein fractions that could serve as useful ingredients for food product development. However, utilization of hemp seed protein fractions in the food industry can only be successful if there is sufficient information on their levels and functional properties. Therefore, this work provides a comparative evaluation of the structural and functional properties of hemp seed protein isolate (HPI) and fractions that contain 2S, 7S, or 11S proteins. HPI and protein fractions were isolated at pH values of least solubility. Results showed that the dominant protein was 11S, with a yield of 72.70 ± 2.30%, while 7S and 2S had values of 1.29 ± 0.11% and 3.92 ± 0.15%, respectively. The 2S contained significantly (p < 0.05) higher contents of sulfhydryl groups at 3.69 µmol/g when compared to 7S (1.51 µmol/g), 11S (1.55 µmol/g), and HPI (1.97 µmol/g). The in vitro protein digestibility of the 2S (72.54 ± 0.52%) was significantly (p < 0.05) lower than those of the other isolated proteins. The intrinsic fluorescence showed that the 11S had a more rigid structure at pH 3.0, which was lost at higher pH values. We conclude that the 2S fraction has superior solubility, foaming capacity, and emulsifying activity when compared to the 7S, 11S, and HPI. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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15 pages, 1006 KiB  
Article
Impact of a Shorter Brine Soaking Time on Nutrient Bioaccessibility and Peptide Formation in 30-Months-Ripened Parmigiano Reggiano Cheese
by Mattia Di Nunzio, Cecilia Loffi, Elena Chiarello, Luca Dellafiora, Gianfranco Picone, Giorgia Antonelli, Clarissa Di Gregorio, Francesco Capozzi, Tullia Tedeschi, Gianni Galaverna and Alessandra Bordoni
Molecules 2022, 27(3), 664; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27030664 - 20 Jan 2022
Cited by 9 | Viewed by 1985
Abstract
Reducing the salt content in food is an important nutritional strategy for decreasing the risk of diet-related diseases. This strategy is particularly effective when applied to highly appreciated food having good nutritional characteristics, if it does not impact either upon sensory or nutritional [...] Read more.
Reducing the salt content in food is an important nutritional strategy for decreasing the risk of diet-related diseases. This strategy is particularly effective when applied to highly appreciated food having good nutritional characteristics, if it does not impact either upon sensory or nutritional properties of the final product. This work aimed at evaluating if the reduction of salt content by decreasing the brine soaking time modifies fatty acid and protein bioaccessibility and bioactive peptide formation in a 30-month-ripened Parmigiano Reggiano cheese (PRC). Hence, conventional and hyposodic PRC underwent in vitro static gastrointestinal digestion, and fatty acid and protein bioaccessibility were assessed. The release of peptide sequences during digestion was followed by LC–HRMS, and bioactive peptides were identified using a bioinformatic approach. At the end of digestion, fatty acid and protein bioaccessibility were similar in conventional and hyposodic PRC, but most of the bioactive peptides, mainly the ACE-inhibitors, were present in higher concentrations in the low-salt cheese. Considering that the sensory profiles were already evaluated as remarkably similar in conventional and hyposodic PRC, our results confirmed that shortening brine soaking time represents a promising strategy to reduce salt content in PRC. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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13 pages, 3212 KiB  
Article
Thermal Shift Assay as a Tool to Evaluate the Release of Breakdown Peptides from Cowpea β-Vignin during Seed Germination
by Stefano De Benedetti, Camilla Leogrande, Francesco Castagna, Giuditta C. Heinzl, Matias Pasquali, Alessandro L. Heinzl, Daniela Lupi and Alessio Scarafoni
Molecules 2022, 27(1), 277; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27010277 - 03 Jan 2022
Cited by 2 | Viewed by 2906
Abstract
The present work aimed to characterize the molecular relationships between structure and function of the seed storage protein β-vignin, the vicilin storage protein of cowpea (Vigna unguiculata, l. Walp) seeds. The molecular characterization of β-vignin was carried out firstly by assessing [...] Read more.
The present work aimed to characterize the molecular relationships between structure and function of the seed storage protein β-vignin, the vicilin storage protein of cowpea (Vigna unguiculata, l. Walp) seeds. The molecular characterization of β-vignin was carried out firstly by assessing its thermal stability, under different conditions of pH and ionic strength, by thermal shift assay (TSA) using SYPRO Orange fluorescent dye. Secondly, its aggregation propensity was evaluated using a combination of chromatographic and electrophoretic techniques. Two forms of β-vignin were considered: the native form purified from mature quiescent seeds, and a stable breakdown intermediate of 27 kDa produced while seeds germinate. TSA is a useful tool for determining and following over time the structural changes that occur to the protein during germination. The main result was the molecular characterization of the 27 kDa intermediate breakdown polypeptide, which, to the best of our knowledge, has never been described before. β-vignin seems to retain its trimeric conformation despite the evident degradation of its polypeptides. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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Review

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17 pages, 25913 KiB  
Review
Beta-Lactoglobulin as a Model Food Protein: How to Promote, Prevent, and Exploit Its Unfolding Processes
by Alberto Barbiroli, Stefania Iametti and Francesco Bonomi
Molecules 2022, 27(3), 1131; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27031131 - 08 Feb 2022
Cited by 6 | Viewed by 4401
Abstract
Bovine milk beta-lactoglobulin (BLG) is a small whey protein that is a common ingredient in many foods. Many of the properties of BLG relevant to the food industry are related to its unfolding processes induced by physical or chemical treatments. Unfolding occurs through [...] Read more.
Bovine milk beta-lactoglobulin (BLG) is a small whey protein that is a common ingredient in many foods. Many of the properties of BLG relevant to the food industry are related to its unfolding processes induced by physical or chemical treatments. Unfolding occurs through a number of individual steps, generating transient intermediates through reversible and irreversible modifications. The rate of formation of these intermediates and of their further evolution into different structures often dictates the outcome of a given process. This report addresses the main structural features of the BLG unfolding intermediates under conditions that may facilitate or impair their formation in response to chemical or physical denaturing agents. In consideration of the short lifespan of the transient species generated upon unfolding, this review also discusses how various methodological approaches may be adapted in exploring the process-dependent structural modifications of BLG from a kinetic and/or a thermodynamic standpoint. Some of the conceptual and methodological approaches presented and discussed in this review can provide hints for improving the understanding of transient conformers formation by proteins present in other food systems, as well as when other physical or chemical denaturing agents are acting on proteins much different from BLG in complex food systems. Full article
(This article belongs to the Special Issue Chemical and Functional Properties of Food Proteins)
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