Amaranth (Amaranthus spp.), buckwheat (Fagopyrum spp.), and quinoa (Chenopodium spp.) proteins: a food science and technology perspective

The use of pseudocereals as raw materials for developing nutritious food products is skyrocketing. Pseudocereals are dicotyledonous crops - unlike true cereals, which are monocotyledonous - with starch-rich seeds. The three major pseudocereals in terms of world production are amaranth, buckwheat, and quinoa. Apart from starch, they contain high levels of protein, dietary fiber, minerals, vitamins, and other bioactive constituents. Their proteins have well-balanced amino acid compositions, are more sustainable than those from animal sources, and can safely be incorporated in the diet of celiac patients. While prolamins and glutelins are the most important protein fractions of true cereals, the proteins of pseudocereals are predominantly albumins and globulins. The traditional Osborne fractionation scheme is not always rigorously followed for pseudocereals, particularly in the methods used to extract globulins and glutelins. It is also of note here that, in order to establish in-depth structure-function relationships, future research should aim at (i) unlocking the genome sequence of pseudocereal proteins and (ii) unraveling the primary, secondary, tertiary, and quaternary structures of amaranth, buckwheat, and quinoa proteins. Basic foaming, emulsifying, and gelling properties of pseudocereal proteins are often similar to or even better than those of industrially relevant protein sources such as casein, which makes them potential substitutes for animal proteins in many food applications. It is, however, imperative to emphasize that, in most studies concerning the functionality of pseudocereal proteins, the protein isolates were obtained by alkaline extraction and subsequent isoelectric precipitation at acidic pH. Such harsh extraction conditions provoke protein denaturation and thus alter the native protein conformation and, as a consequence, the techno-functional properties. Increasing knowledge on structural changes in the native proteins from amaranth, buckwheat, and quinoa during processing steps relevant to food production and the effect thereof on their techno-functional properties is essential to expand the prospects for exploitation of pseudocereals.status: accepte