Development of iron-rich whey protein hydrogels following application of ohmic heating – Effects of moderate electric fields

Abstract

The influence that ohmic heating technology and its associated moderate electric fields (MEF) have upon production of whey protein isolate cold-set gels mediated by iron addition was investigated. Results have shown that combining heating treatments (90°C, 5min) with different MEF intensities let hydrogels with distinctive micro and macro properties - i.e. particle size distribution, physical stability, rheological behavior and microstructure. Resulting hydrogels were characterized (at nano-scale) by an intensity-weighted mean particle diameter of 145nm, a volume mean of 240nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3V∙cm was combined with a cold gelation step using 33mmol∙L of Fe. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10V∙cm. According to transmission electron microscopy, ohmic heating gave rise to a more homogenous and compact fine-stranded whey protein-iron microstructure. Ohmic heating appears to be a promising technique, suitable to tailor properties of whey protein gels and with potential for development of innovative functional foods.

Effects of moderate electric fields on cold-set gelation of whey proteins – From molecular interactions to functional properties

“…Several studies discuss potential additional synergistic or nonthermal effects resulting from the presence of the moderate electric field (MEF) applied during OH processing. Particularly whey protein systems have been the focus of the study of MEF effects on protein aggregation and gelation, demonstrating differentiated properties from conventional heating methods (Pereira et al, 2017(Pereira et al, , 2016Rodrigues et al, 2015). Despite these reports, the specific action of OH (and the inherent MEF) on protein aggregation and gelation remains unclear.…”

Electric field effects on proteins – Novel perspectives on food and potential health implications

“…This gelation strategy consists in unfolding of the protein structure (normally achieved by temperature) followed by shifting the pH or addition of salts which favor the screening of the electrostatic repulsion between charged molecules. Depending on the processing condition, from conventional control (without the presence of an EF) up to 12 Vcm − 1 , it was possible to incorporate 33 mmol•L − 1 of Fe 2+ in the produced protein network, which means that an iron intake of 9 mg/day would be obtained with a daily dose of 5 mL (teaspoon) of the protein gel (Pereira et al, 2017) In addition, this approach allowed modulating viscosity of the produced system bringing opportunities to develop innovative food thickeners.…”

“…heat-sensitive ingredients (Pereira et al, 2018). The application of OH and MEF on the production of WPI cold-set gels mediated by iron addition contributed to the formation of hydrogels with distinctive properties at micro and macro levels such as a more uniform and compact fine-stranded microstructure (Pereira et al, 2017). The formation of cold gel-like emulsions by using OHtreated lactoferrin revealed to produce a more flexible structure when compared to conventional heating (de Figueiredo Furtado, Pereira, Vicente, & Cunha, 2018).…”

Ohmic heating for the dairy industry: a potential technology to develop probiotic dairy foods in association with modifications of whey protein structure

“…electrical field intensity, temperature and time of treatment) it is possible to design protein gel networks for incorporation of functional compounds or nutrients [46]. OH can be used as pre-treatment tool to 'functionalize' globular whey proteins, for development of hydrogels or cold gel-like emulsions [47,48]. Latest reviews about the state-of-art of OH highlight the importance of evaluating the effects of this technology on allergenicity aspects (such as allergy sensitizing or eliciting potential) of food proteins [3 ,15 ].…”