Effect of alkaline extraction on the structure of the protein of quinoa (Chenopodium quinoa Willd.) and its influence on film formation

Abstract

It is important to produce hydrophobic edible protein films for use in foods. The aim of this study was to evaluate the effect of alkaline extraction of quinoa proteins (QP) on the structure and their film-forming ability without plasticiser. QP were extracted between pH 8 to 12, and their structure was evaluated by PAGE-SDS, size-exclusion HPLC light scattering, fluorescence spectroscopy and SH and SS. Film was characterised by FTIR, SEM, tensile strength, barrier and colour. Structural changes of QP showing that alkalinisation over pH 10 produce significant denaturation/aggregation/dissociation structural changes in QP. pH 12 was the condition to form a film (film12). FTIR showed hydrogen bonds and hydrophobic film interactions. Film12 had 16.6 ± 3.8% elongation and 15.7 ± 1.1 MPa tensile strength, and water vapour permeability was 5.18 ± 0.38 g mm m 2 day 1 kPa 1. Film12 had a brownish colour. A high degree of denaturation/aggregation/dissociation of QP structure is required to form a film without plasticiser.