Denaturation of whey proteins of milk during ohmic heating

Ohmic heating has often been said to improve the sensorial quality of foodstuffs, which has been ttributed mainly to its volumetric heating mechanism and (eventually) to the presence of an electric field. This is still subject to doubts and questions from the scientific community, and it is therefore important to determine the effect of ohmic heating on food constituents. We have investigated whether ohmic heating technology would give rise to changes on the denaturation of whey proteins from bovine milk. Whey protein solutions samples were heated at 85 ºC (up to 30 min) and ohmic heating experiments were also adapted to simulate the sample temperature changes during conventional (indirect heating) experiments. Our results show that ohmic heating seems to reduce protein unfolding and denaturation, when compared with conventional heating

Exploring the denaturation of whey proteins upon application of moderate electric fields : a kinetic and thermodynamic study

Thermal processing often results in disruption of the native conformation of whey proteins, thus affecting functional properties. The aim of this work was to evaluate the effects of moderate electric fields on denaturation kinetics and thermodynamic properties of whey protein dispersions at temperatures ranging from 75 to 90 °C. Application of electric fields led to a lower denaturation of whey proteins, kinetically traduced by lower values of reaction order (n) and rate constant (k) (p 30% of native soluble protein than conventional heating) and has determined also considerable changes in calculated thermodynamic properties (such as Ea, ΔH, ΔS). In general, denaturation reactions during moderate electric fields processing were less dependent on temperature increase.RNP gratefully acknowledges a doctoral grant (SFRH/BD/31635/2006) from the Fundacao para Ciencia e Tecnologia (FCT, Portugal

Influence of moderate electric fields on the formation and properties of whey protein network structures

Gelation plays a major role in enhancing textural properties of foods (substituting fats), once it provides unique textural properties that gives pleasant mouth feel, and enables holding water and other ingredients in one matrix. The general objective of this study was to assess the effects of MEF on properties of whey protein hydrogels. Results show that MEF originated a weaker gel structure than conventional heating treatment. Significant decreases in storage and loss moduli were observed upon application of MEF. Aggregation and cross-linking patterns of whey proteins during MEF was not sufficiently high to form a true elastic gel network. As conclusion, MEF may provide a novel method for production of a protein matrix with distinctive properties. However a larger body of research is needed to fully address the role of the MEF on protein electrostatics and protein-protein interactions

Effects of moderate electric fields (MEF) on denaturation of whey proteins solutions

Electric fields application during thermal processing are now receiving increased attention due to uniform heating of liquids and extremely rapid heating rates, which presumably enables higher temperatures to be applied without inducing excessive denaturation of the constituent proteins [1]. The aim of this work was to evaluate the effects of moderate electric fields (MEF) on denaturation kinetics and thermodynamic properties of whey protein dispersions at temperatures ranging from 75 to 90 ºC. Application of MEF led to a lower denaturation of whey proteins, kinetically traduced by lower values of reaction order (n) and rate constant (k) (p 30% of native soluble protein than conventional heating). In general, denaturation reactions during MEF were less dependent on temperature increase presenting higher values of ΔG# in the range of temperatures studied. Further, MEF produced smaller changes (p < 0.05) in whey protein aggregates’ size when compared with a conventional heating MEF offers the potential to change the functional and technological properties of whey proteins, by changing their degree of denaturation. An accurate selection of the MEF process variables may allow controlling the size of protein nanoparticles. These findings could open novel perspectives on the use of OH not only in food and bioprocessing applications, but also in the pharmaceutical area

Comparison of chemical properties of food products processed by conventional and ohmic heating

The effect of ohmic and conventional heat processing of different food products on their chemical and physical parameters was studied. Depending on the food being analysed, parameters such as pH, total solids, ash, titratable acidity, ascorbic acid, total sugars, total fatty acids, total phenolic compounds, and anthocyanins content were determined before and after ohmic and conventional pasteurization techniques and the results were compared using one-way analysis of variance. In goat milk samples treated by ohmic technology the pH value (6.58) and total fatty acids content in milk fat (86.5 mass %) were comparable to those found in milk treated by conventional process, however, ohmically treated samples presented a lower content of lactic acid, 0.13 %. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested, such as total sugar content 46.1 mass %, ascorbic acid content 2.83 mass %, and titratable acidity 6.01 mass % (as citric acid) did not show significant differences when compared with samples treated by conventional technology

Moderate Electric Fields application as a biotechnological tool in food processing

BioTech 2017 and 7th Czech-Swiss Symposium with Exhibition[Excerpt] Moderate Electric Fields (MEF) provide a uniform, rapid and energetically very efficient means of processing foods (mostly by heat). This has been known for over a century and has finally found its place among food processors, as MEF industrial equipments are being installed worldwide in growing numbers and in a variety of applications. This happened after technological issues such as electrode corrosion and adequate temperature and power control systems were solved. [...]info:eu-repo/semantics/publishedVersio

Effects of ohmic heating technology in chemical properties of foods

In this work some food products where characterised chemically before and after ohmic and conventional heating treatments, comparing both processes. In each food type (cloudberry jam, goat milk) pH was measured and parameters such as total and volatile solids, ash, titratable acidity, ascorbic acid, total sugars, total fatty acids, total phenolic compounds and anthocyanins content were determined, depending on the food being analysed. In goat milk samples treated by ohmic technology, the titratable acidity 0.12 % (as lactic acid), pH value 6.59 and total fatty acids content in milk fat 86.5 g 100gˉ¹ were comparable to those found in milk treated by conventional process. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested, such as total sugar content 47.4 g 100gˉ¹, ascorbic acid concentration 2.8 g 100gˉ¹ and titratable acidity 6.01g 100gˉ¹ (as citric acid) did not show significant differences for samples treated by conventional technology

Tortuosity variation in a low density binary particulate bed

The importance of particle size ratio and particle composition in the properties of a mixed bed is well known. Nevertheless, the dependence of the bed channel tortuosity T on the porosity ε in the form T=1/εn, where n is assumed to be a constant, shows that the value of n depends on the properties of the packed bed. For loose packing, experimental data for binary mixtures of glass beads of a size ratio from 1 up to 53.8 was analysed in terms of porosity, tortuosity and permeability. The packing procedure was performed without intensive compacting methods e.g. vibration, etc. Obtained results show that the parameter n is a function of the volume fraction of large particles xD and, for spherical particles, lies in the range 0.4–0.5. The explanation for this variation is (1) a distortion effect on the small particles arrangement occurring near the large particle surface; (2) in the region of minimum porosity, near contact points of large particles, the occurrence of dead zones that are free of small particles. A relationship accounting for this effect is proposed that may be useful for the analysis of transport phenomena in granular bed filters, chromatographic columns, etc.Fundação para a Ciência e a Tecnologia FCT); FEDE