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Homer S, Williams R, Williams A, Logan A. WPI Gel Microstructure and Mechanical Behaviour and Their Influence on the Rate of In Vitro Digestion. Foods 2021; 10:foods10051066. [PMID: 34066220 PMCID: PMC8150613 DOI: 10.3390/foods10051066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/30/2021] [Accepted: 05/04/2021] [Indexed: 11/16/2022] Open
Abstract
The influence of microstructure and mechanical properties on the in vitro digestibility of 15% whey protein isolate (WPI) gels was investigated. Gels were prepared via heat set gelation at three pH values (pH 3, 5 and 7), which produced gels with distinct microstructures and mechanical properties. The gels were minced to simulate an oral/chewing phase, which led to the formation particles of various sizes and textures. The minced gels were passed through either an Infogest (pre-set pH of 3) or Glass stomach (dynamic pH) protocol. Gels were digested in the gastric phase for up to 120 min, at which point the extent of digestion was measured by the amount of filterable nitrogen passing through a sieve. The digesta from both gastric methods were passed through an in vitro simulated intestinal phase. A strong link was found between the elasticity of the initial gel and the gel particle size following simulated oral processing, which significantly (p < 0.01) affected the rate of digestion in the gastric phase. A weaker correlation was also found between the pH of the gels and the extent of gastric digestion. This work highlights the differences in the rate of gastric digestion, arising from oral processing, which can be attributed to the material properties of the substrate.
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Influence of chaperone-like activity of caseinomacropeptide on the gelation behaviour of whey proteins at pH 6.4 and 7.2. Food Hydrocoll 2021. [DOI: 10.1016/j.foodhyd.2020.106249] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Belwal VK, Chaudhary N. Amyloids and their untapped potential as hydrogelators. SOFT MATTER 2020; 16:10013-10028. [PMID: 33146652 DOI: 10.1039/d0sm01578d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Amyloid fibrils are cross-β-sheet-rich fibrous aggregates. They were originally identified as disease-associated protein/peptide deposits. The cross-β motif was consequently labelled as an alien and pathogenic fold. Subsequent research revealed that the fibrillar aggregates were benign, and the cytotoxicity in the amyloid diseases was attributed to the pre-fibrillar structures. Research in the past two decades has identified the native functional amyloids in organisms ranging from bacteria to human. The amyloid-like fibrils, therefore, are not necessarily pathogenic, and the cross-β motif is very much native. This premise makes way for the amyloids to be used as biocompatible materials. Many naturally occurring amyloidogenic proteins/peptides or their fragments have been reported in the literature to form hydrogels. Hydrogels constitute one of the most interesting classes of soft materials that find application in diverse fields such as environmental, electronic, and biomedical engineering. Applications of hydrogels in medicine are particularly extensive. Among various classes of peptides that form hydrogels, the potential of amyloids is largely untapped. In this review, we have attempted to compile the literature on amyloid hydrogels and discuss their potential applications.
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Affiliation(s)
- Vinay Kumar Belwal
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati - 781 039, India.
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Yonaha V, Martinez MJ, Allievi MC, Leskow FC, Pérez OE. Impact of Fat Replacement by Core-shell Microparticles on Set Type Yoghurts: Study of Their Physicochemical, Textural and Microstructural Properties. CURRENT NUTRITION & FOOD SCIENCE 2019. [DOI: 10.2174/1573401314666180503154304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Background: Core-shell micro and nanoparticles can be used to encapsulate bioactive or
functional components and to replace fat content also, since they are able to mimic the organoleptic
characteristics of the fat globules.
</P><P>
Objective: The aim of this study was to investigate the effect of replacing milk fat matter by core-shell
microparticles in set type yoghurt.
</P><P>
Method: Microparticles were produced by electrostatic deposition of carboxymethylcellulose (CMC)
on thermally induced aggregates of β-lactoglobulin (β-lg)n. Laboratory made yoghurts were prepared
with: full fat milk (F), low fat milk (L) and low fat milk with CS microparticles (CS). Yoghurts properties
(e.g. physicochemical, rheological, textural) were characterized during storage at 4 °C. Trials
were also conducted in commercial yoghurts taken as references.
</P><P>
Results: Water holding capacity (WHC) and elastic modulus (G´) of CS yoghurts resulted similar to
commercial yoghurts. Color properties (L*, a*. b*) were slightly altered and showed no significant
variation upon time. CS yoghurts behaved as a weak gel as indicated by the higher n values obtained
from mechanical spectra and by the lower firmness obtained from texture measurements. Important
differences were observed in microstructure. CS yoghurts showed homogeneous aspect with large aggregates
and empty spaces. Bacterial growth in CS yoghurts resulted similar to low fat yoghurts.
</P><P>
Conclusion: Replacement of milk fat by core-shell microparticles would be feasible giving a final
product without major differences, at least instrumentally measurable, to commercial yogurt.
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Affiliation(s)
- Verónica Yonaha
- Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Guiraldes, s/n, Ciudad Universitaria, Buenos Aires, CP 1428, Argentina
| | - María J. Martinez
- Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Consejo Nacional de Investigacion Científica y Tecnicas de la Republica Argentina, ITAPROQ-CONICET, Universidad de Buenos Aires, Intendente Guiraldes, s/n, Ciudad Universitaria, Buenos Aires, CP 1428, Argentina
| | - Mariana C. Allievi
- Departamento de Quimica Biologica, Facultad de Ciencias Exactas y Naturales, Consejo Nacional de Investigacion Científica y Tecnicas de la Republica Argentina IQUIBICEN-CONICET, Universidad de Buenos Aires, Intendente Guiraldes, s/n, Ciudad Universitaria, Buenos Aires, CP 1428, Argentina
| | - Federico Coluccio Leskow
- Departamento de Quimica Biologica, Facultad de Ciencias Exactas y Naturales, Consejo Nacional de Investigacion Científica y Tecnicas de la Republica Argentina IQUIBICEN-CONICET, Universidad de Buenos Aires, Intendente Guiraldes, s/n, Ciudad Universitaria, Buenos Aires, CP 1428, Argentina
| | - Oscar E. Pérez
- Departamento de Quimica Biologica, Facultad de Ciencias Exactas y Naturales, Consejo Nacional de Investigacion Científica y Tecnicas de la Republica Argentina IQUIBICEN-CONICET, Universidad de Buenos Aires, Intendente Guiraldes, s/n, Ciudad Universitaria, Buenos Aires, CP 1428, Argentina
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Homer S, Lundin L, Dunstan DE. A detailed investigation of whey protein isolate solutions and gels reveals a number of novel characteristics. Food Hydrocoll 2018. [DOI: 10.1016/j.foodhyd.2017.10.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Effects of pH modification in proteins from fish (Whitemouth croaker) and their application in food packaging films. Food Hydrocoll 2018. [DOI: 10.1016/j.foodhyd.2017.08.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Ramos OL, Pereira RN, Martins A, Rodrigues R, Fuciños C, Teixeira JA, Pastrana L, Malcata FX, Vicente AA. Design of whey protein nanostructures for incorporation and release of nutraceutical compounds in food. Crit Rev Food Sci Nutr 2017; 57:1377-1393. [PMID: 26065435 DOI: 10.1080/10408398.2014.993749] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Whey proteins are widely used as nutritional and functional ingredients in formulated foods because they are relatively inexpensive, generally recognized as safe (GRAS) ingredient, and possess important biological, physical, and chemical functionalities. Denaturation and aggregation behavior of these proteins is of particular relevance toward manufacture of novel nanostructures with a number of potential uses. When these processes are properly engineered and controlled, whey proteins may be formed into nanohydrogels, nanofibrils, or nanotubes and be used as carrier of bioactive compounds. This review intends to discuss the latest understandings of nanoscale phenomena of whey protein denaturation and aggregation that may contribute for the design of protein nanostructures. Whey protein aggregation and gelation pathways under different processing and environmental conditions such as microwave heating, high voltage, and moderate electrical fields, high pressure, temperature, pH, and ionic strength were critically assessed. Moreover, several potential applications of nanohydrogels, nanofibrils, and nanotubes for controlled release of nutraceutical compounds (e.g. probiotics, vitamins, antioxidants, and peptides) were also included. Controlling the size of protein networks at nanoscale through application of different processing and environmental conditions can open perspectives for development of nanostructures with new or improved functionalities for incorporation and release of nutraceuticals in food matrices.
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Affiliation(s)
- Oscar L Ramos
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal.,b LEPABE-Laboratory of Engineering of Processes, Environment, Biotechnology and Energy, University of Porto, Rua Dr. Roberto Frias , Porto , Portugal
| | - Ricardo N Pereira
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
| | - Artur Martins
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
| | - Rui Rodrigues
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
| | - Clara Fuciños
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal.,c Biotechnology Group , Department of Analytical Chemistry and Food Science , University of Vigo , Ourense , Spain
| | - José A Teixeira
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
| | - Lorenzo Pastrana
- c Biotechnology Group , Department of Analytical Chemistry and Food Science , University of Vigo , Ourense , Spain
| | - F Xavier Malcata
- b LEPABE-Laboratory of Engineering of Processes, Environment, Biotechnology and Energy, University of Porto, Rua Dr. Roberto Frias , Porto , Portugal.,d Department of Chemical Engineering , Rua Dr. Roberto Frias , Porto , Portugal
| | - António A Vicente
- a CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
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Properties of partially denatured whey protein products: Formation and characterisation of structure. Food Hydrocoll 2016. [DOI: 10.1016/j.foodhyd.2015.06.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Singh TK, Øiseth SK, Lundin L, Day L. Influence of heat and shear induced protein aggregation on the in vitro digestion rate of whey proteins. Food Funct 2014; 5:2686-98. [DOI: 10.1039/c4fo00454j] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Protein intake is essential for growth and repair of body cells, the normal functioning of muscles, and health related immune functions.
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Affiliation(s)
| | | | - Leif Lundin
- CSIRO Animal
- Food and Health Sciences
- Werribee, Australia
| | - Li Day
- CSIRO Animal
- Food and Health Sciences
- Werribee, Australia
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12
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Woo HD, Moon TW, Gunasekaran S, Ko S. Determining the gelation temperature of β-lactoglobulin using in situ microscopic imaging. J Dairy Sci 2013; 96:5565-74. [DOI: 10.3168/jds.2013-6786] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 06/09/2013] [Indexed: 11/19/2022]
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13
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Haug I, Carlsen AM, Vegarud G, Langsrud T, Draget K. Textural Properties of Beta-lactoglobulin - Sodium Alginate Mixed Gels at Large Scale Deformation. J Texture Stud 2012; 44:56-65. [DOI: 10.1111/j.1745-4603.2012.00365.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/18/2012] [Indexed: 11/28/2022]
Affiliation(s)
- I.J. Haug
- Norwegian Biopolymer Laboratory (NOBIPOL); Institute of Biotechnology; Norwegian University of Science and Technology (NTNU); N-7491; Trondheim; Norway
| | - A.-M.H. Carlsen
- Norwegian Biopolymer Laboratory (NOBIPOL); Institute of Biotechnology; Norwegian University of Science and Technology (NTNU); N-7491; Trondheim; Norway
| | - G.E. Vegarud
- Institute of Chemistry, Biotechnology and Food Science (IKBM); Norwegian University of Life science (UMB); Aas; Norway
| | - T. Langsrud
- Institute of Chemistry, Biotechnology and Food Science (IKBM); Norwegian University of Life science (UMB); Aas; Norway
| | - K.I. Draget
- Norwegian Biopolymer Laboratory (NOBIPOL); Institute of Biotechnology; Norwegian University of Science and Technology (NTNU); N-7491; Trondheim; Norway
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von Staszewski M, Jara FL, Ruiz AL, Jagus RJ, Carvalho JE, Pilosof AM. Nanocomplex formation between β-lactoglobulin or caseinomacropeptide and green tea polyphenols: Impact on protein gelation and polyphenols antiproliferative activity. J Funct Foods 2012. [DOI: 10.1016/j.jff.2012.05.008] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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15
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Leksrisompong PN, Foegeding EA. How Micro-Phase Separation Alters the Heating Rate Effects on Globular Protein Gelation. J Food Sci 2011; 76:E318-27. [DOI: 10.1111/j.1750-3841.2011.02092.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Viscoelastic and Thermal Properties of Collagen–Xanthan Gum and Collagen–Maltodextrin Suspensions During Heating and Cooling. FOOD BIOPHYS 2009. [DOI: 10.1007/s11483-009-9110-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Mehalebi S, Nicolai T, Durand D. The influence of electrostatic interaction on the structure and the shear modulus of heat-set globular protein gels. SOFT MATTER 2008; 4:893-900. [PMID: 32907196 DOI: 10.1039/b718640a] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Gels formed by the globular protein β-lactoglobulin after heat denaturation were studied using light scattering, turbidity and shear oscillation measurements. The structure of the gels was characterized in terms of the amplitude and the correlation length of concentration fluctuations. The strength of electrostatic interactions was varied by changing the pH in the absence of added salt or by changing the NaCl concentration at pH 7. A very strong increase of the heterogeneity of the gels was observed when decreasing the pH towards the isoelectric point or when increasing the salt concentration. The structural change was interpreted in terms of a decrease of the net repulsion between the growing aggregates leading to increased concentration fluctuations and finally microscopic phase separation. The elastic shear modulus increased with decreasing pH and showed a maximum as a function of the NaCl concentration. No direct correlation between the change in the structure and the elastic modulus was found.
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Affiliation(s)
- Soraya Mehalebi
- Polymères, Colloïdes, Interfaces, UMR CNRS Université du Maine, 72085 Le Mans cedex 9, France.
| | - Taco Nicolai
- Polymères, Colloïdes, Interfaces, UMR CNRS Université du Maine, 72085 Le Mans cedex 9, France.
| | - Dominique Durand
- Polymères, Colloïdes, Interfaces, UMR CNRS Université du Maine, 72085 Le Mans cedex 9, France.
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21
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da Silva MA, Arêas EPG. Solvent-induced lysozyme gels: rheology, fractal analysis, and sol-gel kinetics. J Colloid Interface Sci 2006; 289:394-401. [PMID: 15935361 DOI: 10.1016/j.jcis.2005.04.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 04/07/2005] [Accepted: 04/07/2005] [Indexed: 11/28/2022]
Abstract
In this work, the gelation kinetics and fractal character of lysozyme gel matrices developed in tetramethylurea (TMU)-water media were investigated. Gelation times were determined from the temporal crossover point between the storage, G', and loss, G'', moduli, as a function of the binary solvent composition and of protein concentration. The inverse dependence of the upper limit of the linear viscoelastic region (gamma0) on protein concentration indicate that the lysozyme gels belong to the "strong link" kind, a gel category where interparticle links are stronger than intraparticle ones. Lysozyme gel fractal dimensions (Df) were determined from the analysis of rheological data according to a scaling theory by Shih et al. [Phys. Rev. A 42 (1990) 4772-4779] and were found to be compatible with a diffusion-limited cluster-aggregation kinetics (DLCA) for lysozyme gels formed at the TMU mass fraction in the binary organic-aqueous solvent, wTMU=0.9, and with a reaction-limited cluster aggregation kinetics (RLCA) for wTMU in the 0.6< or =wTMU< or =0.8 range.
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Affiliation(s)
- Marcelo A da Silva
- Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Caixa Postal 26077, CEP 05513-970 São Paulo, SP, Brazil
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Abstract
Protein aggregation is a problem with a multitude of consequences, ranging from affecting protein expression to its implication in many diseases. Of recent interest is the specific form of aggregation leading to the formation of amyloid fibrils, structures associated with diseases such as Alzheimer's disease. The ability to form amyloid fibrils is now regarded as a property generic to all polypeptide chains. Here we show that around the isoelectric point a different generic form of aggregation can also occur by studying seven widely different, nonrelated proteins that are also all known to form amyloid fibrils. Under these conditions gels consisting of relatively monodisperse spherical particulates are formed. Although these gels have been described before for beta-lactoglobulin, our results suggest that the formation of particulates in the regime where charge on the molecules is minimal is a common property of all proteins. Because the proteins used here also form amyloid fibrils, we further propose that protein misfolding into clearly defined aggregates is a generic process whose outcome depends solely on the general properties of the state the protein is in when aggregation occurs, rather than the specific amino acid sequence. Thus under conditions of high net charge, amyloid fibrils form, whereas under conditions of low net charge, particulates form. This observation furthermore suggests that the rules of soft matter physics apply to these systems.
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Affiliation(s)
- Mark R H Krebs
- Sector of Biological and Soft Systems, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
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Bromley EHC, Krebs MRH, Donald AM. Mechanisms of structure formation in particulate gels of beta-lactoglobulin formed near the isoelectric point. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 21:145-52. [PMID: 17151833 DOI: 10.1140/epje/i2006-10055-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2006] [Accepted: 11/02/2006] [Indexed: 05/12/2023]
Abstract
Particulate gels are known to be formed by bovine beta-lactoglobulin near the isoelectric point when partial unfolding is allowed to occur under heating. The aggregation process of the protein has been investigated within the context of a nucleation and growth process by preparing gels under precisely controlled thermal histories. This was achieved using a Differential Scanning Calorimeter (DSC) to provide controlled heating rates, and known final temperatures and incubation times. The resulting particulate gels were characterized by their particle size and polydispersity using Environmental Scanning Electron Microscopy (ESEM), which permits hydrated samples to be observed. Particle size was found to decrease with increasing final temperature, with the aggregation taking longer to reach completion for lower temperatures. Particle size was also found to decrease with increasing heating rate. This system could be modelled as evolving via nucleation and growth by taking into account the fact that the concentration of the aggregating species was varying as a function of temperature as well as time. The intrinsic tryptophan fluorescence as a function of temperature was used as a guide to the fraction of unfolded protein in solution, thereby permitting successful comparisons between the model predictions and the particle sizes to be made.-1.
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Affiliation(s)
- E H C Bromley
- Cavendish Laboratory, University of Cambridge, Madingley Road, CB3 0HE, Cambridge, UK.
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Resch JJ, Daubert CR, Foegeding EA. β-Lactoglobulin Gelation and Modification: Effect of Selected Acidulants and Heating Conditions. J Food Sci 2006. [DOI: 10.1111/j.1365-2621.2005.tb09025.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kerstens S, Murray BS, Dickinson E. Microstructure of β-lactoglobulin-stabilized emulsions containing non-ionic surfactant and excess free protein: Influence of heating. J Colloid Interface Sci 2006; 296:332-41. [PMID: 16168425 DOI: 10.1016/j.jcis.2005.08.046] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 08/19/2005] [Accepted: 08/21/2005] [Indexed: 11/15/2022]
Abstract
The influence of the non-ionic surfactant Tween 20 on the microstructure of beta-lactoglobulin-stabilized emulsions with substantial excess free protein present was investigated via confocal microscopy. The separate distributions of oil droplets and protein were determined using two different fluorescent dyes. In the emulsion at ambient temperature the excess protein and protein-coated oil droplets were associated together in a reversibly flocculated state. The pore-size distribution of the initial flocculated emulsion was found to depend on the surfactant/protein ratio R, and at higher values of R the system became more inhomogeneous due to areas of local phase separation. Evidence for competitive displacement of protein from the oil-water interface by surfactant was obtained only on heating (from 25 to 85 degrees C) during the process of formation of a heat-set emulsion gel. By measuring fluorescence intensities of the protein dye inside and outside of the oil-droplet-rich areas, we have been able to quantify the evolving protein distribution during the thermal processing. The results are discussed in relation to previous work on the competitive adsorption of proteins and surfactants in emulsions and the effect of emulsion droplets on the rheology of heat-set protein gels.
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Affiliation(s)
- Sven Kerstens
- Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, UK
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26
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Baier SK, McClements DJ. Influence of Cosolvent Systems on the Gelation Mechanism of Globular Protein: Thermodynamic, Kinetic, and Structural Aspects of Globular Protein Gelation. Compr Rev Food Sci Food Saf 2005; 4:43-54. [DOI: 10.1111/j.1541-4337.2005.tb00072.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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CHEN JIANSHE, MOSCHAKIS THOMAS, NELSON PHILIP. APPLICATION OF SURFACE FRICTION MEASUREMENTS FOR SURFACE CHARACTERIZATION OF HEAT-SET WHEY PROTEIN GELS. J Texture Stud 2005. [DOI: 10.1111/j.1745-4603.2004.35502.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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28
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Bromley EH, Krebs MRH, Donald AM. Aggregation across the length-scales in β-lactoglobulin. Faraday Discuss 2005; 128:13-27. [PMID: 15658764 DOI: 10.1039/b403014a] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The protein beta-lactoglobulin (BLG) has been widely studied, in large part because of its importance to the food industry. Following denaturation during heating, under different conditions of pH it has been found to form either particulate (around the isoelectric point at pH 5.1) or fibrillar gels. The nature of the fibrils has recently been suggested to be the same as that identified with amyloid fibrils known for a wide-range of different proteins and implicated in many disease states. We confirm that the BLG fibrils show all the classical signatures of amyloid fibrils. In addition, the fibrils are capable themselves of aggregating further to form large-scale (many microns in size) spherulites. Polarized light microscopy and Environmental scanning electron microscopy (ESEM) have been used to explore the internal structure of these spherulites under conditions in which the solvent has not been dried off. The factors which determine whether or not the spherulites form have also been considered, together with implications for other amyloid-containing systems.
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Arnaudov LN, de Vries R, Ippel H, van Mierlo CPM. Multiple Steps during the Formation of β-Lactoglobulin Fibrils. Biomacromolecules 2003; 4:1614-22. [PMID: 14606887 DOI: 10.1021/bm034096b] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, the heat induced fibrilar aggregation of the whey protein beta-lactoglobulin is investigated at low pH and at low ionic strength. Under these circumstances, tapping mode atomic force microscopy results indicate that the fibrils formed have a periodic structure with a period of about 25 nm and a thickness of one or two protein monomers. Fibril formation is followed in situ using light scattering and proton NMR techniques. The dynamic light scattering results show that the fibrils that form after short heating periods (up to a few hours) disintegrate upon slow cooling, whereas fibrils that form during long heating periods do not disintegrate upon subsequent slow cooling. The NMR results show that even after prolonged heating an appreciable fraction of the protein molecules is incorporated into fibrils only when the beta-lactoglobulin concentration is above approximately 2.5 wt %. The data imply multiple steps during the heat induced formation of beta-lactoglobulin fibrils at low pH and at low ionic strength: (partly) denatured protein monomers are either incorporated into fibrils or form instead a low molecular weight complex that is incapable of forming fibrils. Fibril formation itself also involves (at least) two steps: the reversible formation of linear aggregates, followed by a slow process of "consolidation" after which the fibrils no longer disintegrate upon slow cooling.
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Affiliation(s)
- Luben N Arnaudov
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6700 EK Wageningen, The Netherlands
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Baeza R, Gugliotta LM, Pilosof A. Gelation of β-lactoglobulin in the presence of propylene glycol alginate: kinetics and gel properties. Colloids Surf B Biointerfaces 2003. [DOI: 10.1016/s0927-7765(03)00045-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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31
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Remondetto GE, Subirade M. Molecular mechanisms of Fe2+-induced beta-lactoglobulin cold gelation. Biopolymers 2003; 69:461-9. [PMID: 12879492 DOI: 10.1002/bip.10423] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To get more insight into the mechanisms of cold gelation of beta-lactoglobulin (beta-lg), macroscopic and molecular structural changes during Fe(2+)-induced gelation of beta-lg were investigated using Fourier transform-infrared (FTIR) spectroscopy and rheological methods. The FTIR spectroscopy results show that, upon the preheating treatment (first step of gel process), native globular proteins are denatured and aggregated molecules are found in solution. The spectra are similar to those of gels obtained in the second step of the process upon incorporation of Fe, which suggests that aggregated molecules formed during the preheating treatment constitute the structural basis of the aggregation. However, the rheological data show that the aggregation is achieved via two molecular mechanisms, both of which are modulated by the iron concentration. At 30 mM of iron, gel formation is essentially controlled by van der Waals interactions, while at 10 mM of iron, hydrophobic interactions predominate. At the two concentrations, disulfide bonds contribute to gel consolidation, the effect being more pronounced at 10 mM of iron. These mechanisms lead to the formation of gels of different microstructures. At the highest iron concentration, a strong and rapid decrease in the repulsion forces is produced, resulting in random aggregation. At the lowest iron concentration, the iron diminishes the superficial charge of both molecules and aggregated molecules, facilitating the interaction among hydrophobic regions and leading to the growth of the aggregation in the preferential direction and to filamentous gel formation. This study provides a comprehensive view of the different modes of gelation.
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Affiliation(s)
- Gabriel E Remondetto
- Centre de recherche en science et technologie du lait (STELA), Institut des nutraceutiques et des aliments fonctionnels (INAF), Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, Pavillon Paul Comtois, Québec, Canada, G1K 7P4
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32
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Vittayanont M, Steffe JF, Flegler SL, Smith DM. Gelation of chicken pectoralis major myosin and heat-denatured beta-lactoglobulin. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2003; 51:760-765. [PMID: 12537454 DOI: 10.1021/jf020413e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Thermal, rheological, and microstructural properties of myosin (1 and 2% protein) were compared to mixtures of 1% myosin and 1% heat-denatured beta-lactoglobulin aggregates (myosin/HDLG) and 1% myosin and 1% native beta-lactoglobulin (myosin/beta-LG) in 0.6 M NaCl and 0.05 M sodium phosphate buffer, pH 6.0, 6.5, and 7.0 during heating to 71 degrees C. Thermal denaturation patterns of myosin and myosin/HDLG were similar except for the appearance of an endothermic peak at 54-56 degrees C in the mixed system. At pH 7.0, 2% myosin began to gel at 48 degrees C and had a storage modulus (G') of 500 Pa upon cooling. Myosin/HDLG (2% total protein) had a gel point of 48 degrees C and a G' of 650 Pa, whereas myosin/beta-LG had a gel point of 49 degrees C but the G' was lower (180 Pa). As the pH was decreased, the gel points of myosin and myosin/HDLG decreased and the G' after cooling increased. The HDLG was incorporated within the myosin gel network, whereas beta-LG remained soluble.
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Affiliation(s)
- Manee Vittayanont
- Department Food Science and Human Nutrition and Center for Advanced Microscopy, Michigan State University, East Lansing, Michigan 48824-1224, USA
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33
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Löfgren C, Walkenström P, Hermansson AM. Microstructure and rheological behavior of pure and mixed pectin gels. Biomacromolecules 2002; 3:1144-53. [PMID: 12425650 DOI: 10.1021/bm020044v] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The microstructure and the rheological properties of pure HM (high methoxyl) and LM (low methoxyl) pectin gels and of mixed HM/LM pectin gels have been investigated. Gel formation of either the HM or LM pectin, or both, was initiated in the mixed gels by varying the sucrose and Ca(2+) content. The microstructure was characterized by transmission electron microscopy, light microscopy, and confocal laser scanning microscopy. HM and LM pectin gels showed aggregated networks with large pores around 500 nm and network strands of similar character. Small differences could be found, such as a more inhomogeneous LM pectin network with shorter and more branched strands of flexible appearance. LM pectin also formed a weak gel in 60% sucrose in the absence of calcium. A highly inhomogeneous mixed gel structure was formed in the presence of 60% sucrose and Ca(2+) ions, which showed large synergistic effects in rheological properties. Its formation was explained by the behavior of the corresponding pure gels. In the presence of 60% sucrose alone, a homogeneous, fine-stranded mixed network was formed, which showed weak synergistic effects. It is suggested that LM pectin interacts with HM pectin during gel formation, thereby hindering secondary aggregation leading to the aggregated networks observed for the pure gels.
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Affiliation(s)
- Caroline Löfgren
- SIK, The Swedish Institute for Food and Biotechnology, PO Box 5401, 402 29 Göteborg, Sweden
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34
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Sagis LM, Veerman C, Ganzevles R, Ramaekers M, Bolder SG, van der Linden E. Mesoscopic structure and viscoelastic properties of β-lactoglobulin gels at low pH and low ionic strength. Food Hydrocoll 2002. [DOI: 10.1016/s0268-005x(01)00084-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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35
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Ikeda S, Morris VJ. Fine-stranded and particulate aggregates of heat-denatured whey proteins visualized by atomic force microscopy. Biomacromolecules 2002; 3:382-9. [PMID: 11888326 DOI: 10.1021/bm0156429] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
beta-Lactoglobulin and whey protein isolate (WPI) were heated in aqueous solutions at pH 2 and 7 at 80 degrees C, spread onto freshly cleaved mica surfaces, and visualized under butanol using atomic force microscopy. Fine-stranded aggregates were formed at pH 2, the diameter of strands being ca. 4 nm for beta-lactoglobulin and 10 nm for WPI. At pH 7, aggregates were composed of ellipsoidal particles, regardless of the concentration of added NaCl. This observation supports the previously proposed two-step aggregation model at neutral pH (Aymard, P.; Gimel, J. C.; Nicolai, T.; Durand, D. J. Chim. Phys. 1996, 93, 987-997), consisting of the formation of primary globular particles and the subsequent aggregation of those primary particles. The AFM provides the first direct evidence for the anisotropic shape of these primary particles. The heights of primary particles increased from ca. 11 to 27 nm with increasing concentrations of added NaCl from 0 to 0.3 M in the case of WPI. The rate of aggregation was also accelerated with increasing NaCl concentrations, which appeared to induce transitions in gel networks from fine-stranded toward particulate networks. The present study provides structural information essential for understanding the diverse physical properties of heat-induced whey protein gels.
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Affiliation(s)
- Shinya Ikeda
- Department of Food and Nutrition, Osaka City University, Sumiyoshi, Osaka 558-8585, Japan.
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36
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37
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Vittayanont M, Vega-Warner V, Steffe JF, Smith DM. Heat-induced gelation of chicken Pectoralis major myosin and beta-lactoglobulin. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2001; 49:1587-1594. [PMID: 11312900 DOI: 10.1021/jf000774z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The denaturation, aggregation, and rheological properties of chicken breast muscle myosin, beta-lactoglobulin (beta-LG), and mixed myosin/beta-LG solutions were studied in 0.6 M NaCl, 0.05 mM sodium phosphate buffer, pH 7.0, during heating. The endotherm of a mixture of myosin and beta-LG was identical to that expected if the endotherm of each protein was overlaid on the same axis. The maximum aggregation rate (AR(max)) increased, and the temperature at the AR(max) (T(max)) and initial aggregation temperature (T(o)) decreased as the concentration of both proteins was increased. The aggregation profile of <0.5% myosin was altered by the presence of 0.25% beta-LG. Addition of 0.5-3.0% beta-LG decreased storage moduli of 1% myosin between 55 and 75 degrees C, but increased storage moduli (G') when heated to 90 degrees C and after cooling. beta-LG had no effect on the gel point of > or =1.0% myosin, but enhanced gel strength when heated to 90 degrees C and after cooling. After cooling, the G' of 1% myosin/2%beta-LG gels was about 1.7 times greater than that of gels prepared from 2% myosin/1% beta-LG.
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Affiliation(s)
- M Vittayanont
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824-1224, USA
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38
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Lopez C, Dufour E. The Composition of the Milk Fat Globule Surface Alters the Structural Characteristics of the Coagulum. J Colloid Interface Sci 2001; 233:241-249. [PMID: 11121272 DOI: 10.1006/jcis.2000.7255] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of the composition of a fat globule surface in reconstituted milks on the properties of rennet-induced coagulums were studied by rheological measurements and by front-face fluorescence spectroscopy in combination with a multivariate statistical method to investigate, at a molecular level, the evolution of the structure during the milk coagulation process. Reconstituted milks used in this study were prepared from different fat-in-water emulsions stabilized by whole skim-milk proteins, beta-casein, or beta-lactoglobulin. Coagulation of milk reconstituted with natural fat globules was also investigated. The study showed that the fat droplet/water interface influences the rheological properties (G' modulus) of the reconstituted milks during the coagulation process. The tryptophan fluorescence emission spectra of proteins were recorded during the kinetics of coagulation. The results of the principal component analysis performed on the spectral data showed a discrimination in the different systems investigated. It was shown that the fluorescence properties of protein tryptophans and, consequently, the structures of the protein networks were different for the investigated systems. The development of fluorescence transfer between protein tryptophans and fat-globule vitamin A during the coagulation kinetics agreed with the interactions between the protein network and fat globules. Copyright 2001 Academic Press.
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Affiliation(s)
- C Lopez
- Laboratoire d'Etude des Interactions des Molécules Alimentaires, Institut National de la Recherche Agronomique, Nantes Cedex 03, 44316, France
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39
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Kavanagh GM, Clark AH, Ross-Murphy SB. Heat-induced gelation of globular proteins: part 3. Molecular studies on low pH beta-lactoglobulin gels. Int J Biol Macromol 2000; 28:41-50. [PMID: 11033176 DOI: 10.1021/la0004698] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Heat-set gels and aggregates from beta-lactoglobulin (beta-Lg), one of the major globular proteins from milk, have been studied on a molecular distance scale using negative-staining transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared spectroscopy (FTIR). The microscopy showed long linear aggregates forming in solutions at pH 2 (and sometimes 2.5) after prolonged heating. While there appeared to be no differences in aggregates formed under these conditions in H(2)O as compared with D(2)O, at all other pH and pD values, and in the presence of added salt, much shorter linear aggregates were formed. These became slightly more extended the further the pH was removed from pI. Wide-angle X-ray diffraction (WAXD) showed a diffuse beta-sheet halo at 2θ=19 degrees in patterns for both dried native and aggregated protein (irrespective of pH) with only a small change (sharpening) of this feature on heat treatment. Solution FTIR spectra, measured at pD=2, 2.5, 3, and 7, during heating, indicated shoulder development at 1612 cm(-1) in the carbonyl-stretching Amide I region diagnostic of a modest increase in intermolecular beta-sheet. In terms of the shoulder size, no distinctions could be made between acid and neutral aggregate structures. At all pHs, beta-lactoglobulin showed only limited secondary and tertiary structural changes in aggregation, in contrast to previous studies of insulin aggregation, where highly ordered crystalline fibrils were indicated. The current work has implications both in structural studies of food biopolymers and in ongoing studies of pathological protein self-assembly in disease states, such as spongiform encephalopathies.
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Affiliation(s)
- G M Kavanagh
- Division of Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, Waterloo, SE1 8WA, London, UK
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40
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Kavanagh GM, Clark AH, Gosal WS, Ross-Murphy SB. Heat-Induced Gelation of β-Lactoglobulin/α-Lactalbumin Blends at pH 3 and pH 7. Macromolecules 2000. [DOI: 10.1021/ma0005522] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gaynor M. Kavanagh
- Biopolymers Group, Division of Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 8WA, U.K., and Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1lQ, UK
| | - Allan H. Clark
- Biopolymers Group, Division of Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 8WA, U.K., and Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1lQ, UK
| | - Walraj S. Gosal
- Biopolymers Group, Division of Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 8WA, U.K., and Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1lQ, UK
| | - Simon B. Ross-Murphy
- Biopolymers Group, Division of Life Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 8WA, U.K., and Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1lQ, UK
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41
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Anker M, Stading M, Hermansson AM. Relationship between the microstructure and the mechanical and barrier properties of whey protein films. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2000; 48:3806-3816. [PMID: 10995275 DOI: 10.1021/jf000040m] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This work was focused on the relationship between the microstructure and the mechanical and barrier properties of whey protein isolate (WPI) films. Sorbitol (S) and glycerol (G) were used as plasticizers and the pH was varied between 7 and 9. The films were cast from heated aqueous solutions and dried in a climate room at 23 degrees C and 50% relative humidity for 16 h. The microstructure of the films was found to be dependent on the concentration, the plasticizers, and the pH. When the concentration increased, a more aggregated structure was formed, with a denser protein network and larger pores. This resulted in increased water vapor permeability (WVP) and decreased oxygen permeability (OP). When G was used as a plasticizer instead of S, the microstructure was different, and the moisture content and WVP approximately doubled. When the pH increased from 7 to 9, a denser protein structure was formed, the strain at break increased, and the OP decreased.
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Affiliation(s)
- M Anker
- SIK-The Swedish Institute for Food and Biotechnology, P.O. Box 5401, SE-402 29 Göteborg, Sweden
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42
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Mechanical Properties and Microstructure of Heat-set Whey Protein Emulsion Gels: Effect of Emulsifiers. Lebensm Wiss Technol 2000. [DOI: 10.1006/fstl.2000.0656] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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43
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Renard D, Robert P, Garnier C, Dufour E, Lefebvre J. Gelation by phase separation in a whey protein system: in-situ kinetics of aggregation. J Biotechnol 2000; 79:231-44. [PMID: 10867184 DOI: 10.1016/s0168-1656(00)00240-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aggregation and gelation properties of beta-lactoglobulin (BLG), a globular protein from milk, was studied in aqueous ethanol solutions at room temperature. The phase state diagrams as a function of pH and ethanol concentration showed that a gel structure appeared after a period ranging from 1 min to 1 week, depending on the physico-chemical conditions. The in-situ kinetics of aggregation were followed by several methods in order to obtain a better understanding of the building of aggregates by the addition of ethanol. It was shown that the aggregation kinetics highly depended upon the pH, the process being fastest at pH 7. Viscoelasticity and infrared measurements indicated that alcohol-induced gelation would proceed via a two-step mechanism: small aggregates loosely connected between them were first built up; a real network took place in a second step. The coarse and irregular structures formed in aqueous ethanol gels revealed by confocal laser scanning microscopy could be analysed in terms of a phase separation. This observation was supported by a syneresis phenomenon visible in the final gel state. BLG in water-ethanol solution would undergo either an inhibition of the demixing by gelation or a binary phase separation accompanied by an irreversible gelation transition.
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Affiliation(s)
- D Renard
- Unit¿e de Physico-Chimie des Macromol¿ecules, Centre de Recherches INRA, Rue de la G¿eraudi¿ere, BP 71627-44316 Cedex 3, Nantes, France.
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44
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Neiser S, Draget K, Smidsrød O. Interactions in bovine serum albumin–calcium alginate gel systems. Food Hydrocoll 1999. [DOI: 10.1016/s0268-005x(99)00019-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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45
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Capron I, Nicolai T, Smith C. Effect of addition of κ-carrageenan on the mechanical and structural properties of β-lactoglobulin gels. Carbohydr Polym 1999. [DOI: 10.1016/s0144-8617(99)00058-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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46
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Renard D, Lefebvre J, Robert P, Llamas G, Dufour E, Dufour E. Structural investigation of beta-lactoglobulin gelation in ethanol/water solutions. Int J Biol Macromol 1999; 26:35-44. [PMID: 10520954 DOI: 10.1016/s0141-8130(99)00060-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The aggregation and gelation properties of beta-lactoglobulin (BLG), a globular protein from milk, was studied in hydro-ethanolic solutions (50/50% (v/v)) at room temperature. The phase state diagrams as a function of pH and ethanol concentration showed that a gel structure appeared after a period ranging from 1 min to 1 week depending on the physico-chemical conditions. The aggregation kinetics, studied by infrared spectroscopy and dynamical rheological measurements, highly depended upon the pH; the process being the fastest at pH 7. Alcohol-induced aggregation of BLG was characterized by the formation of intermolecular hydrogen bonded beta-sheet structures. Small angle neutron scattering indicated that the aggregates structures in the final gels were similar at pH 7, 8 and 9. Through the data obtained at the molecular and macroscopic levels, it can be concluded that the kinetics of gelation were pH dependent while the spatial arrangements of the aggregates were similar in the final structures. The heterogeneous structures formed in hydro-ethanolic gels could be analysed in terms of a phase separation, the syneresis being the final visible state.
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Affiliation(s)
- D Renard
- Laboratoire de Physico-Chimie des Marcromolécules, Institut National de la Recherche Agronomique, Nantes, France.
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47
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Stading M, Langer R. Mechanical shear properties of cell-polymer cartilage constructs. TISSUE ENGINEERING 1999; 5:241-50. [PMID: 10434071 DOI: 10.1089/ten.1999.5.241] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cartilaginous constructs were created by using bovine chondrocytes on synthetic, biodegradable scaffolds made of fibrous polyglycolic acid (PGA). The constructs have previously been shown to resemble natural articular cartilage biochemically and histologically. The mechanical properties of articular cartilage mainly depend on the swollen extracellular matrix (ECM), which is a gel consisting of collagen fibers and proteoglycans in a fluid phase of water and electrolytes. The biomechanical properties of the constructs and the build-up of the ECM were studied using dynamic, nondestructive measurements in shear. A small, harmonic strain, lambda < or = 5 x 10(-4), was applied to the sample, and the resulting stress was recorded and used for calculating the complex shear modulus G*. The applied strain was much smaller than that used in confined compression. The shear modulus G* correlated well with both the collagen and glycosaminoglycan content of the constructs but did not reach the same level as in natural cartilage. Collagen is the dominant component contributing to the shear strength of cartilage, and G* was shown to depend approximately quadratically on the collagen content of the constructs. The difference in G* between the constructs and natural cartilage was shown to depend on both the biochemical composition and the microstructure of the constructs. () ()
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Affiliation(s)
- M Stading
- Chalmers University of Technology/SIK, The Swedish Institute for Food and Biotechnology, Göteborg, Sweden.
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48
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Anker M, Stading M, Hermansson AM. Effects of pH and the gel state on the mechanical properties, moisture contents, and glass transition temperatures of whey protein films. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 1999; 47:1878-1886. [PMID: 10552465 DOI: 10.1021/jf981115d] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The mechanical properties, moisture contents (MC), and glass transition temperature (T(g)) of whey protein isolate (WPI) films were studied at various pH values using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 degrees C and 50% relative humidity (RH) for 16 h. The critical gel concentrations (c(g)) for the cooled aqueous solutions were found to be 11.7, 12.1, and 11.3% (w/w) WPI for pH 7, 8, and 9, respectively. The cooling rate influenced the c(g), in that a lower amount of WPI was needed for gelation when a slower cooling rate was applied. Both cooling rates used in this study showed a maximum in the c(g) at pH 8. The influence of the polymer network on the film properties was elucidated by varying the concentration of WPI over and under the c(g). Strain at break (epsilon(b)) showed a maximum at the c(g) for all pH values, thus implying that the most favorable structure regarding the ability of the films to stretch is formed at this concentration. Young's modulus (E) and stress at break (sigma(b)) showed a maximum at c(g) for pH 7 and 8. The MC and epsilon(b) increased when pH increased from 7 to 9, whereas T(g) decreased. Hence, T(g) values were -17, -18, and -21 degrees C for pH 7, 8, and 9, respectively. E and sigma(b) decreased and epsilon(b) and thickness increased when the surrounding RH increased. The thickness of the WPI films also increased with the concentration of WPI.
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Affiliation(s)
- M Anker
- SIK-The Swedish Institute for Food and Biotechnology, Göteborg, Sweden
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49
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Aymard P, Nicolai T, Durand D, Clark A. Static and Dynamic Scattering of β-Lactoglobulin Aggregates Formed after Heat-Induced Denaturation at pH 2. Macromolecules 1999. [DOI: 10.1021/ma981689j] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Pierre Aymard
- Chimie et Physique des Matériaux Polymères, UMR CNRS, Université du Maine, 72085 Le Mans Cedex 9, France
| | - Taco Nicolai
- Chimie et Physique des Matériaux Polymères, UMR CNRS, Université du Maine, 72085 Le Mans Cedex 9, France
| | - Dominique Durand
- Chimie et Physique des Matériaux Polymères, UMR CNRS, Université du Maine, 72085 Le Mans Cedex 9, France
| | - Allan Clark
- Unilever Research Colworth, Sharnbrook, Bedford, MK441LQ, U.K
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50
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Walkenström P, Windhab E, Hermansson AM. Shear-induced structuring of particulate whey protein gels. Food Hydrocoll 1998. [DOI: 10.1016/s0268-005x(98)00064-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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