Ohmic vs. conventional heating: Influence of moderate electric fields on properties of potato protein isolate gels

The influence of moderate electric fields (MEF) on thermally induced gelation and network structures of patatin enriched potato protein (PPI) was investigated. PPI solutions with 9 wt% protein (pH 7) and 25 mM NaCl were heated from 25 to 65 °C via OH (3–24 V/cm) or conventional heating (COV) at various come-up (240 s and 1200 s) and holding times (30 s and 600 s). Self-standing gels were produced but less proteins denatured when heated via OH. Further, SDS-PAGE and GPC measurements revealed more native patatin remaining after OH treatment. Scanning electron microscopy showed OH gels to have more gap-like structures and frayed areas than COV treated gels which resulted in lower water holding capacity. On molecular scale, less hydrophobic interactions were measured within the protein network and FTIR trials showed the MEF to affect beta-sheet structures. OH gels further showed lower rigidity and higher flexibility, thus, gelling functionality was affected via OH.

Industrial relevance: Ohmic heating (OH) is an advanced heating technology which has gained interest within the last decades as it is a highly energy and time efficient way to heat up foods. Additionally, as OH does not require any fossil energies, OH is considered to be a sustainable heating option for the food processing industry. During OH, electrical current is converted into heat within the food. However, it is not fully understood yet, whether OH influences the food matrix compared to conventional heating and how OH impacts certain ingredients, e.g. globular proteins and their denaturation/ gelation. This study helps to provide knowledge facilitating an implementation of OH into industry processes, serving a more sustainable food production. To evaluate the influence of OH on protein gelation, a patatin enriched potato protein was chosen as this protein offers a high protein functionality and therefore is of high interest for food industry (e.g. to be used as ingredient for plant based foods).