Structure of whey protein gels, studied by permeability, scanning electron microscopy and rheology

Verheul, Marleen; Roefs, S.P.F.M.

doi:10.1016/s0268-005x(98)00041-1

Cited by 118 publications

(97 citation statements)

References 20 publications

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“…The possible explanation for this is that heating the whey protein solutions above 60°C, provokes complex changes of the molecular conformation and undergo denaturation (Aymard et al, 1999). Similarly as discussed in the HIWPG formation, this leads the protein molecules to exhibit hydrophobic areas on its surface (Cantor and Schimmel, 1980;Verheul and Roef, 1998;Galani and Apenten, 1999). The denaturation of whey proteins particularly β-lactoglobulin is considered by many e.g.…”

Section: The Effect Of Heating/run Time On Whey Protein Solution Foulingmentioning

confidence: 99%

“…Upon heating the whey protein solution forms a gel due to the reaction between the proteins molecules in the matrix forming many small monomers. These protein monomers contain a number of cysteine residues (Sawyer et al, 1985;Brownlow et al, 1997) and upon heating the free -SH groups of cysteine residues get oxidized and form disulfide bonds (Verheul and Roef, 1998;Galani and Apenten, 1999). These bonds are involved in cross-linking the protein monomers to form the aggregates (Galani and Apenten, 1999).…”

Section: Effect Of Heating Time On Hiwpg Formationmentioning

confidence: 99%

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Influence of Run Time and Aging on Fouling and Cleaning of Whey Protein Deposits on Heat Exchanger Surface

Fickak¹,

Hatfield

Chen

2012

JFR

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In the cleaning operations of heat exchange surfaces in dairy processing plants, the effect of heating/run time (HT) and aging on the fouling/cleaning of heat exchangers is not well understood. Longer heating time of the same deposit is expected to result in the formation of stronger and perhaps more cleaning resistant deposit. In this study, the phenomenon of heating and aging on the formation and cleaning of dairy fouling is investigated using the heat induced whey protein gels (HIWPG) produced in laboratory. The processes were also investigated with the whey protein deposits formed in pilot-scale plant trails.The HIWPGs were produced in tubular capsules for various heating (or run) times (60, 120, 240, 1440 and 2880 min respectively) and then dissolved in aqueous sodium hydroxide (0.5 wt %). The heating process here would have been of 'pure' aging. The dissolution rate was calculated based on the previously established UV Spectrophotometer analysis. The structure and texture of the gels were analysed using Scanning Electron Microscope (SEM) and texture analyser. In the pilot-scale plant study, whey protein fouling layers were generated by recirculating whey protein solution (6 wt %) for various heating periods (30, 60, and 90 min respectively). The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt %) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as indications of cleaning completion. It was found that increasing the HIWPG heating time significantly increased the gel hardness and dissolution time, implicating the difficulty in cleaning. Similarly to these results on gels, increasing the pilot-scale plant heating/run time increased the extent of fouling. The fouling layer formed next to the metal surface experienced the longest period of aging and the slope of the heat transfer coefficient increase seen at the final cleaning stage is related to this aging effect. The rate of cleaning for deposits formed initially on the metal surface is lower indicating a 'pure' aging effect of the deposit near surface.

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Section: The Effect Of Heating/run Time On Whey Protein Solution Foulingmentioning

confidence: 99%

Section: Effect Of Heating Time On Hiwpg Formationmentioning

confidence: 99%

Influence of Run Time and Aging on Fouling and Cleaning of Whey Protein Deposits on Heat Exchanger Surface

Fickak¹,

Hatfield

Chen

2012

JFR

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“…Figure modified from "Phase segregation of amylopectin and β-lactoglobulin in aqueous system" 16 process starts to occur even at room temperature, and that close to the isoelectric point (pI) of the βlg, protein interactions are favored. This results in βlg aggregation which is predominant over the denaturation, 30,31 and the process could perhaps be accelerated if the protein already has some degree of denaturation. The concentration of the protein increases during film formation and therefore the interaction of the protein molecules increases too, which lead to the aggregation of the protein molecules.…”

Section: One-component System: Amylopectin System and β-Lactoglobulinmentioning

confidence: 99%

Characterization of the Microstructure of Phase Segregated Amylopectin and β-Lactoglobulin Dry Mixtures

Quiroga

Bergenståhl

2007

Food Biophysics

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The microstructure of phase-segregated amylopectin (AP) and β-lactoglobulin (βlg) mixtures formed during drying from solutions with different concentrations and different polysaccharide and protein ratios have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). AFM was used as the main technique and TEM was used to confirm the results. Systems with only one of the components, AP or βlg, displayed even structures. When the polysaccharide and the protein were in the same system they phase segregated with a sharp boundary between the phases. According to the type of surface morphology of the phase-segregated samples, they were grouped into: domains wetting the airwater surface and domains appearing to be immersed in the solid film. The size range of the domains varied widely from about some nanometers to about a few micrometers which was determined by kinetic reasons or by restrictions given by the film structure of the sample. The two phase systems were AP-continuous phase at AP to βlg ratios above about 1:3 and βlg-continuous phase at ratios below about 1:6. Between these ratios, the systems appeared more or less bicontinuous. The morphology as well as its position in the phase diagram suggested a spinodal phase separation. Phase separation was also observed in the metastable region (AP to βlg ratio 3:1), although the domains were smaller and less developed and it was interpreted as binodal phase separation.

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“…Gelation is achieved via junction zones formed by helices, forming a threedimensional network (Hemar et al, 2002). Interactions between biopolymers (protein-protein, protein-polysaccharide and/or protein-solvent) are controlled as a function of system composition (Verheul and Roefs, 1998;Mleko, et al, 1997) or process condition, such as heat treatment (Capron, et al, 1999;Ju and Kilara, 1998) and shear (Walkenström, et al, 1998). These interactions can be evaluated by rheological measurements.…”

Section: Introductionmentioning

confidence: 99%

The effects of sucrose on the mechanical properties of acid milk proteins-kappa-carrageenan gels

Sabadini

Hubinger

Cunha

2006

Braz. J. Chem. Eng.

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-Mechanical properties have been widely correlated with textural characteristics to determine the interactions during the process formation of dairy gel. These interactions are strongly affected by process conditions and system composition. In the present study, the rheological of acid-induced protein dairy gels with (2 (7-3) ) and without (2 (6-2) ) sucrose and subjected to small and large deformations were studied using an experimental design. The independent variables were the sodium caseinate, whey protein concentrate (WPC), carrageenan and sucrose concentrations as well as stirring speed and heat treatment time and temperature. Mechanical deformation tests were performed at 0.1, 1, 5, and 9 mm/s up to 80% of initial height. A heavy dependence of rupture stress on increasing crosshead speed and the formation of harder gels with the addition of sucrose were observed. Moreover the elastic and viscous moduli, obtained by fitting the Maxwell model to stress relaxation data, increased with increasing addition of sucrose. These results can be explained by preferential hydration of the casein with sucrose, causing an induction of casein-polysaccharide and caseincasein interactions.

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Structure of whey protein gels, studied by permeability, scanning electron microscopy and rheology

Cited by 118 publications

References 20 publications

Influence of Run Time and Aging on Fouling and Cleaning of Whey Protein Deposits on Heat Exchanger Surface

Influence of Run Time and Aging on Fouling and Cleaning of Whey Protein Deposits on Heat Exchanger Surface

Characterization of the Microstructure of Phase Segregated Amylopectin and β-Lactoglobulin Dry Mixtures

The effects of sucrose on the mechanical properties of acid milk proteins-kappa-carrageenan gels

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