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

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 degrees C, 5 min) 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 145 nm, a volume mean of 240 nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3 V.cm(-1) was combined with a cold gelation step using 33 mmol.L-1 of Fe2+. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10 V.cm(-1). 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.