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Backbone asymmetric structure of casein submicelle with water from droplet algorithm, 2823 water molecules; κ-CN in blue, α s1-CN in red, β-CN magenta, and water molecules yellow green.
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Recent advances in the field of protein chemistry have significantly enhanced our understanding of the possible intermediates that may occur during protein folding and unfolding. In particular, studies on alpha-lactalbumin have led to the theory that the molten globule state may be a possible intermediate in the folding of many proteins. The molten...
Citations
... It has been reported that scCO 2 can promote changes in interfacial and surface properties, leading to a partially unfolded structure of proteins known as a molten globule, which is characterized by a somewhat compact structure and a high degree of hydration and side-chain flexibility, with the exposure of buried hydrophobic residues. Additionally, the molten globule state retains a significant amount of native secondary structure but exhibits limited tertiary folds [42,43]. In this sense, the lower solubility of PESC at pH 5 to 9 could be promoted by the molten globule state adopted by different protein species in the extract. ...
Tomato seeds are a rich source of protein that can be utilized for various industrial food purposes. This study delves into the effects of using supercritical CO2 (scCO2) on the structure and techno-functional properties of proteins extracted from defatted tomato seeds. The defatted meal was obtained using hexane (TSMH) and scCO2 (TSMC), and proteins were extracted using water (PEWH and PEWC) and saline solution (PESH and PESC). The results showed that scCO2 treatment significantly improved the techno-functional properties of protein extracts, such as oil-holding capacity and foaming capacity (especially for PEWC). Moreover, emulsifying capacity and stability were enhanced for PEWC and PESC, ranging between 4.8 and 46.7% and 11.3 and 96.3%, respectively. This was made possible by the changes in helix structure content induced by scCO2 treatment, which increased for PEWC (5.2%) and decreased for PESC (8.0%). Additionally, 2D electrophoresis revealed that scCO2 hydrolyzed alkaline proteins in the extracts. These findings demonstrate the potential of scCO2 treatment in producing modified proteins for food applications.
... This hydrophobicity plot could give an indication of (1) which AA of human αS1-casein could be exposed, (2) whether S 33 , S 41 , S 71 and S 89 could be accessible for phosphorylation, and (3) which parts of αS1-casein were more hydrophobic and could be involved in intra-and/or intermolecular binding (e.g., to other human caseins). Human αS1-casein contained more hydrophilic AA at the N-terminus, especially at AAS [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45], and the C-terminus (at AAS 170-185) compared to bovine αS1-casein. Human αS1-casein was more hydrophobic at positions 83-102 compared to bovine αS1-casein. ...
... K D value was not obtained for dimer formation. The K D value of unphosphorylated α S1 -casein binding to itself was in the same order of magnitude as the K D value of 2 µM for dephosphorylated bovine α S1 -casein determined by SPR [21] and postulated K D values for all bovine caseins between 1 and 3 µM [21,42]. ...
Breast-milk αS1-casein is a Toll-like receptor 4 (TLR4) agonist, whereas phosphorylated αS1-casein does not bind TLR4. The objective of this study was to analyse the structural requirements for these effects. In silico analysis of αS1-casein indicated high α-helical content with coiled-coil characteristics. This was confirmed by CD-spectroscopy, showing the α-helical conformation to be stable between pH 2 and 7.4. After in vitro phosphorylation, the α-helical content was significantly reduced, similar to what it was after incubation at 80 °C. This conformation showed no in vitro induction of IL-8 secretion via TLR4. A synthetic peptide corresponding to V77-E92 of αS1-casein induced an IL-8 secretion of 0.95 ng/mL via TLR4. Our results indicate that αS1-casein appears in two distinct conformations, an α-helical TLR4-agonistic and a less α-helical TLR4 non-agonistic conformation induced by phosphorylation. This is to indicate that the immunomodulatory role of αS1-casein, as described before, could be regulated by conformational changes induced by phosphorylation.
... In previous studies [4,5], researchers observed that enzymatic destabilization of casein micelles leads to their transformation into a "molten globule" state, accompanied by micelle swelling, which is visually clear through an increase in their size. It signifies the initial stage of subsequent conformational changes. ...
The aim of this study is to enhance the comprehension of the mechanism of enzymatic gelation in milk by visualizing the evolution of its microstructure through transmission electron microscopy. In order to minimize the potential for artifacts during the preparation process and eliminate any possible difficulties in interpreting the resulting images, three distinct methods were employed in the research: shading the surface topography with vacuum deposition of heavy metal, negative staining of the specimen with a heavy metal solution and replicating a cleavage of a quick-frozen sample. The selection of time intervals for sampling the gel during its evolution is determined by the most probable significant modifications in the resulting gel. Based on the research, it has been shown that natural milk is a nonequilibrium system from the perspective of statistical thermodynamics. A notable observation is that the glycomacropeptides forming the hair layer on the surface of casein micelles are unevenly distributed, leading to the formation of micelle dimers and trimers. It has been determind that during the initial stage of enzymatic gelation in milk, clusters of loosely bound micelles are formed in areas with the highest concentration. The formation of micelle chains is absent at this stage due to the non-anisometric nature of micelles and the energetic disadvantage of their formation. It has been found that under the influence of enzymatic gelation near the gel point, a hierarchical process involving the transformation of the milk’s protein component is activated. The trigger mechanism for this process is a cooperative conformational transition in clusters of casein micelles, which initiates a chain of more energy-intensive reactions in the following sequence: hydrophobic interactions → hydrogen bridges → electrostatic interactions → calcium bridges. The result is the conversion of loosely bound micelle clusters into denser aggregates, predominantly contributing to the formation of milk curd. It is worth noting that gelation in milk can be regarded as a process that reduces the free energy of the dispersed system. Understanding the correlation between the decrease in the free energy value during gelation and the physical properties of the finished cheese and other dairy products continues to be a relevant area of research.
... The architectures of filamentous proteins are flexible and disordered; casein, for example, contains a coil shape having regions of both hydrophobic as well as hydrophilic amino acids (Farrell Jr et al., 2002). When combined with calcium phosphate, casein produces giant colloidal particles known as casein micelles (Bhat et al., 2016;Broyard & Gaucheron, 2015). ...
Proteins serve as an important nutritional as well as structural component of foods. Not only do they provide an array of amino acids necessary for maintaining human health but also act as thickening, stabilizing, emulsifying, foaming, gelling, and binding agents. The ability of a protein to possess and demonstrate such unique functional properties depends largely on its inherent structure, configuration, and how it interacts with other food constituents like polysaccharides, lipids, and polyphenolic compounds. Proteins from animal sources have superior functionality, higher digestibility, and lower antinutrient components than plant proteins. However, consumer preferences are evolving worldwide for ethically and sustainably sourced, clean, cruelty-free, vegan, or vegetarian plant-based food products. Unlike proteins from animal sources, plant proteins are more versatile and religiously and culturally acceptable among vegetarian and vegan consumers and associated with lower food-processing waste, water, and soil requirement. Thus, the processing and utilization of plant proteins have gained worldwide attention, and as such numerous scientific studies are focusing on enhancing the utilization of plant proteins in food and pharmaceutical products through various processing and modification techniques to improve their techno-functional properties, bioactivity, bioavailability, and digestibility. Novel Plant Protein Processing: Developing the Foods of the Future presents a roadmap for plant protein science and technology which will focus on plant protein ingredient development, plant protein modification, and the creation of plant protein-based novel foods. KEY FEATURES • Includes complete information about novel plant protein processing to be used in future foods • Presents a roadmap to upscale the meat analog technological processes • Discusses marketing limitations of plant-based proteins and future opportunities This book highlights the important scientific, technological advancements that are being deployed in the future foods using plant proteins, concerns, opportunities, and challenges and as an alternative to maintaining a healthy and sustainable modern food supply. It covers the most recent research related to the plant protein-based future foods which include their extraction, isolation, modification, characterization, development, and final applications. It also covers the formulation and challenges: emphasis on the modification for a specific use, legal aspects, business perspective, and future challenges. This book is useful for researchers, readers, scientists, and industrial people to find information easily.
... Fibrous or meat proteins have a complex structure of fibrous protein bundles positioned inside connective tissue formed of triple helices of collagen, and can be classified as sarcoplasmic, stromal (elastin, collagen), and myofibrillar protein (actin, myosin, tropomyosin, troponins) [19,20]. Lastly, filamentous proteins have flexible and disorderly structures; for instance, casein has a random coil structure, with hydrophobic and hydrophilic patches [21]. Due to its structure, casein links to calcium phosphate molecules to form casein micelles [22,23]. ...
... The initial aggregation of rennet-hydrolyzed casein micelles in this phase is confirmed by a series of micrographs obtained by different authors [5,6]. It is also noted that at the end of the enzymatic phase, cooperative conformational phase transitions occur in casein molecules, which drastically change the properties of casein micelles [7,8,9]. ...
The purpose of this work is to describe and study the previously unknown phenomenon of self-segmentation of a milk curd in an open-type cheesemaking tank. Based on the analysis of the kinetics of gel formation, it has been determined that self-segmentation of the gel begins near the gel point, develops over several tens of seconds, and becomes stable as the gel condenses. The segments in the milk curd do not have a definite regular shape; their average size varies from 5 to 50 cm. The shape and size of the segments do not repeat and do not correlate with the type of cheese being produced. The displacement of the segments of the milk curd in the cheesemaking tank relative to each other in height is from 0.5 to 2 mm. The width of the boundary layer between the curd segments increases during the secondary phase of gelation from 3 to 10 mm. As a result of experimental studies, it has been shown that self-segmentation of milk gel is caused by thermogravitational convection, which forms Benard convection cells. A description of a possible mechanism of milk gel self-segmentation in open-type cheesemaking tanks is proposed. The effective role of fat globules in the mechanism of self-segmentation of the milk curd has been noted. It has been suggested that self-segmentation of the milk curd in the cheesemaking tank may cause some organoleptic defects in the finished cheese, in particular inhomogeneity of texture and color.
... Shown are the aromatic amino acid (AA) residues (containing phenylalanine, tryptophan, and tyrosine) plus leucine and methionine residues, as well as the number of proline residues, which act as structural disruptors [33]. The numbers of amino acid residues were taken from literature a [34], b [35], and c [36]. The percentage composition of the beta-sheets and alpha-helices is derived from literature d [37], e [38], f [39], g [40], and h [41], and the number of disulfide bonds in the tertiary structure is from literature i [42]. ...
In this meta-analysis, we collected 58 publications spanning the last seven decades that
reported static in vitro protein gastric digestion results. A number of descriptors of the pepsinolysis
process were extracted, including protein type; pepsin activity and concentration; protein concentration;
pH; additives; protein form (e.g., ‘native’, ‘emulsion’, ‘gel’, etc.); molecular weight of the
protein; treatment; temperature; and half-times (HT) of protein digestion. After careful analysis and
the application of statistical techniques and regression models, several general conclusions could be
extracted from the data. The protein form to digest the fastest was ‘emulsion’. The rate of pepsinolysis
in the emulsion was largely independent of the protein type, whereas the gastric digestion of the
native protein in the solution was strongly dependent on the protein type. The pepsinolysis was
shown to be strongly dependent on the structural components of the proteins digested—specifically,
�-sheet-inhibited and amino acid, leucine, methionine, and proline-promoted digestion. Interestingly,
we found that additives included in the digestion mix to alter protein hydrolysis had, in general, a
negligible effect in comparison to the clear importance of the protein form or additional treatment.
Overall, the findings allowed for the targeted creation of foods for fast or slow protein digestion,
depending on the nutritional needs.
... Filamentous proteins have flexible and disorderly structures; for instance, casein has a random coil structure, with hydrophobic and hydrophilic patches [45]. Casein forms large colloidal particles with calcium phosphate to form casein micelles [46,47]. ...
Protein calories consumed by people all over the world approximate 15–20% of their energy intake. This makes protein a major nutritional imperative. Today, we are facing an unprecedented challenge to produce and distribute adequate protein to feed over nine billion people by 2050, in an environmentally sustainable and affordable way. Plant-based proteins present a promising solution to our nutritional needs due to their long history of crop use and cultivation, lower cost of production, and easy access in many parts of the world. However, plant proteins have comparatively poor functionality, defined as poor solubility, foaming, emulsifying, and gelling properties, limiting their use in food products. Relative to animal proteins, including dairy products, plant protein technology is still in its infancy. To bridge this gap, advances in plant protein ingredient development and the knowledge to construct plant-based foods are sorely needed. This review focuses on some salient features in the science and technology of plant proteins, providing the current state of the art and highlighting new research directions. It focuses on how manipulating plant protein structures during protein extraction, fractionation, and modification can considerably enhance protein functionality. To create novel plant-based foods, important considerations such as protein–polysaccharide interactions, the inclusion of plant protein-generated flavors, and some novel techniques to structure plant proteins are discussed. Finally, the attention to nutrition as a compass to navigate the plant protein roadmap is also considered.
... In addition, the manufacture and properties of cheeses and yogurts are strongly influenced by the characteristics of the casein molecules and micelles present in cow's milk (Chandan & Kilara, 2013;Fox, Guinee, Cogan, & McSweeney, 2016). Caseins have a highly flexible almost random coil structure, with hydrophobic and hydrophilic patches and numerous phosphate groups (Farrell et al., 2002). The caseins associate with each other to form threedimensional networks in yogurt and cheese that lead ...
Consumers are increasingly demanding foods that are more ethical, sustainable and nutritious to improve the health of themselves and the planet. The food industry is currently undergoing a revolution, as both small and large companies pivot toward the creation of a new generation of plant‐based products to meet this consumer demand. In particular, there is an emphasis on the production of plant‐based foods that mimic those that omnivores are familiar with, such as meat, fish, egg, milk, and their products. The main challenge in this area is to simulate the desirable appearance, texture, flavor, mouthfeel, and functionality of these products using ingredients that are isolated entirely from botanical sources, such as proteins, carbohydrates, and lipids. The molecular, chemical, and physical properties of plant‐derived ingredients are usually very different from those of animal‐derived ones. It is therefore critical to understand the fundamental properties of plant‐derived ingredients and how they can be assembled into structures resembling those found in animal products. This review article provides an overview of the current status of the scientific understanding of plant‐based foods and highlights areas where further research is required. In particular, it focuses on the chemical, physical, and functional properties of plant‐derived ingredients; the processing operations that can be used to convert these ingredients into food products; and, the science behind the formulation of vegan meat, fish, eggs, and milk alternatives.
... The A 81 − K 113 region in bovine α S2 -casein is similar in several respects to the fibril core region in bovine κ-casein [60], particularly the A 23 − F 55 region of κ-casein, as noted previously [27,67]. Both regions have a low net charge owing mainly to an abundance of P, Q, Y and L residues. ...
Bovine milk αS2-casein, an intrinsically disordered protein, readily forms amyloid fibrils in vitro and is implicated in the formation of amyloid fibril deposits in mammary tissue. Its two cysteine residues participate in the formation of either intra- or intermolecular disulphide bonds, generating monomer and dimer species. X-ray solution scattering measurements indicated that both forms of the protein adopt large, spherical oligomers at 20 °C. Upon incubation at 37 °C, the disulphide-linked dimer showed a significantly greater propensity to form amyloid fibrils than its monomeric counterpart. Thioflavin T fluorescence, circular dichroism and infrared spectra were consistent with one or both of the dimer isomers (in a parallel or antiparallel arrangement) being predisposed toward an ordered, amyloid-like structure. Limited proteolysis experiments indicated that at least part of the A⁸¹ − K¹¹³ region is incorporated into the fibril core, implying that this region, which is predicted by several algorithms to be amyloidogenic, initiates fibril formation of αS2-casein. The partial conservation of the cysteine motif and the frequent occurrence of disulphide-linked dimers in mammalian milks despite the associated risk of mammary amyloidosis, suggest that the dimeric conformation of αS2-casein is a functional, yet amyloidogenic, structure.
