Denaturation and in Vitro Gastric Digestion of Heat-Treated Quinoa Protein Isolates Obtained at Various Extraction pH

Abstract

The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components.

Structural prope rties, functional evaluation, and in vitro protein digestibility of black and yellow quinoa (Chenopodium petiolare) protein isolates

“…There were no statistical differences in the final protein extraction yield (PY%) between flours; but for the case of solid yield (SY%), the YQF showed a higher value, indicating that some other compounds (non-protein based) were coextracted during the protein extraction step. Regarding PY%, our results are similar to the reported by Brinegar and Goundan (1993), with 47% of final protein extraction, but lower in comparison with the 74.3% obtained by Avila Ruiz et al (2016) and the 76.3% reached by Guerreo-Ochoa et al (2015) at pH 11 using NaCl (0.1 N). In the production of protein isolates, several parameters such as protein content of the raw material, thermal treatment of the flour, chemical composition, as well as the conditions used during the extraction process can significantly influence production yields.…”

“…Lipids are known to diminish protein extraction due to the formation of protein-lipid emulsions, even when lipids are present in low contents. In a study conducted by Ruiz et al (2016), protein isolates were obtained from deffated quinoa of the sweet cultivar Atlas harvested in Santiago, Chile. They described protein extraction yields from 24 to 37% when the procedure was conducted at pH 8 and 11, respectively.…”

The Influence of Starch and Fibre on In Vitro Protein Digestibility of Dry Fractionated Quinoa Seed (Riobamba Variety)

“…This could explain the lower protein digestibility obtained with QPI. This effect by aggregation was previously suggested by Opazo-Navarrete et al [20] and Avila et al [31] who found that quinoa protein preheated at 120°C had lower gastric digestibility as a consequence of protein aggregation.…”

Availability of potato protein concentrate as an alternative protein source to fish meal in greater amberjack ( Seriola dumerili ) diets

“…Furthermore, Xie et al () showed that protein digestibility reached 93% in Gibel carp fed a diet comprising 32% PPC, which is equivalent to that of FM. From these results, the protein digestibility of PPC is not necessarily inferior to that of FM, and the decrease in protein digestibility with increasing PPC concentration observed in our study was probably due to poor PPC processing and heating conditions, since changes in digestibility depend on processing conditions, such as purification, extraction and heating (Ruiz et al, ). This also applies to PPC digestibility; therefore, it seems necessary to develop processing methods that maximize protein digestibility.…”