Cold gel-like emulsions of lactoferrin subjected to ohmic heating

Abstract

Ohmic heating is a technique that has gained increasing attention because of its capacity to produce uniform heating, and claimed electrical influence on the functional and technological properties of treated protein dispersions. The aim of this work was to evaluate the influence of ohmic heating on the properties of cold gel-like emulsions, comparing them with those obtained by conventional heating. The effect of ohmic and conventional heating on physical and structural properties of lactoferrin was also addressed. Ohmic heating treatment resulted in less pronounced aggregation of lactoferrin, when compared to conventional heating. An increase of particle size, turbidity, intrinsic and extrinsic fluorescence values and a decrease of dichroic signal after heat treatment indicated an increase of protein interactions. Emulsions produced from heat-treated lactoferrin showed gel-like behavior which was related to the emulsifying capacity of lactoferrin, combined with the emulsification method and the heat pre-treatment applied to the protein. Rheological and microstructural properties were intrinsically related to the heat treatment of the protein since ohmic heating produced gel-like emulsions with a less rigid structure. These emulsions could be interesting for food applications containing heat-sensitive ingredients.

Design of β-lactoglobulin micro- and nanostructures by controlling gelation through physical variables

“…This difference in fluorescence intensity as a function of heating time may be related to changes in the compactness of the protein molecule due to local molecular unfolding, thus increasing the accessibility of buried tryptophan residues (Royer, 2006). This behavior has been also observed by Bourbon et al (2015) for lactoferrin and lactoferrin-GMP nanohydrogels when heated at 80°C up to 20 min and by Furtado et al (2018) for lactoferrin solutions when heated at 90°C up to 30 min. For extrinsic fluorencence (Fig.…”

“…Circular dichroism (CD) spectroscopy provides information and consequently less accessible on the main secondary structural elements (i.e., α-helix, β-sheet and coil) of proteins, through measurement of polarized light absorbed by peptide bonds (Monteiro et al, 2016). The α-helix structure is characterized by displaying an intense and positive band at 190 nm and negative peaks at 208 and 220 nm, the β-sheet structure typically presents a negative peak with a minimum in the 215 nm region, while random coil structures display a positive peak close to 215 nm and a negative one near to 200 nm (Furtado, Pereira, Vicente, & Cunha, 2018). The values recorded from 190 to 260 nm for purified and commercial β-Lg in native state is depicted in Fig.…”

Effects of different nut oils on the structures and properties of gel‐like emulsions induced by ultrasound using soy protein as an emulsifier

“…4). It could be seen that the storage modulus (G′) of all samples were higher than those of loss modulus (G′′), which confirmed the formation of elastic gel‐like emulsions (de Figueiredo Furtado et al ., 2018). Furthermore, the G′ and G′′ of samples presented weak dependencies on frequency, indicating the formation of permanent interactions, leading to the predominant solid behaviour of gel‐like emulsions (Furtado et al ., 2018).…”

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

“…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). The impact of MEF effects on WPI from molecular to macroscopic levels was recently established.…”