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

Abstract

Summary 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.

Adhesive Performance of Camelina Protein Affected by Extraction Conditions

“…Camelina protein extracted at high alkaline pH typically has more negative charges due to ionization of carboxyl groups and deprotonation of amine groups. The subsequent increased electrostatic repulsion among protein promotes protein-water interaction, thereby increasing protein solubility (Valenzuela et al, 2013;Lawal, 2004). The highest solubility of camelina protein occurred at pH 12, which was consistent with previous work (Li et al, 2014).…”

“…Higher pH treatment generated more exposure of S-H bond and thiolate (S-), which were able to form intermolecular S-S bonds. Valenzuela et al (2013) and Abugoch et al (2008) also reported that extreme alkaline treatment caused protein aggregates to be stabilized by disulfide bonds. Figure 3 shows two endothermic denaturation peaks at low extraction pH (pH 8 to 10) in the thermograms of camelina protein, indicating that two main protein fractions differed by denaturation temperature in the camelina protein extracts.…”

A Hybrid Dry and Aqueous Fractionation Method to Obtain Protein-Rich Fractions from Quinoa (Chenopodium quinoa Willd)

“…To stimulate more extensive use and create added value of (sweet) quinoa in the production of foods, ingredients derived from quinoa by fractionation have been explored by several studies, in particular, the production of protein isolates (Brinegar and Goundan 1993;Brinegar et al 1996;Chauhan et al 1999;Aluko and Monu 2003;Lindeboom 2005;Abugoch et al 2008;Aora and Alvarado 2009;Valenzuela et al 2013;Föste et al 2015;Avila Ruiz et al 2016a, b). In all these studies, the conventional wet fractionation method was applied.…”

Shelf‐life of fresh blueberries coated with quinoa protein/chitosan/sunflower oil edible film

“…The TS value of the Q/CH/SO film was 0.45 ± 0.29 MPa, which was lower than values found for CH or Q/CH films . The incorporation of SO into the polymeric matrix decreases TS values, and this property is also affected by the pH at which Q extraction takes place . On the other hand, the % E value was 117.2 ± 7.6, which was higher than values from CH .…”