Quinoa (Chenopodium quinoa Wild.) is a plant species belonging to the Chenopodiaceae family, which originated in the Andes region of South America. Quinoa seeds generally have a small grain size (1.8–2.2 mm) which contains high amounts of protein, lipid, and ash. Their extraordinary adaptability to climate and soil conditions makes it increasingly popular. Presently, quinoa is cultivated widely across the globe, including in Europe, North America, North Africa, and Asia [1,2]. Currently, more than 250 varieties of quinoa seeds are grown, and their chemical and nutritional compositions are greatly impacted by genetic diversity, geographic locations, and cultivating environmental conditions [3]. In the terms of uses, quinoa seeds have been most often used in direct cooking, being incorporated into the food formula as an ingredient in bakery products [4], steamed bread [5], and meat products [6]; in addition, its nutritional components, such as protein, polysaccharides, saponins, etc., are extracted. Quinoa seeds have multiple properties, such as anti-oxidative, anti-inflammatory, immunomodulatory, anticarcinogenic, etc. [7]. The composition of polysaccharides in quinoa seeds is more similar to that of fruits and vegetables; therefore, quinoa polysaccharides are considered prebiotic due to their capability of increasing beneficial bacteria growth [8]. Additionally, quinoa seeds have been proven to be beneficial for reducing obesity [9]. Although quinoa seeds have general characteristics, like cereals do, quinoa is normally considered as a pseudocereal due to its different botanical traits from cereals such as wheat, rye, barley, etc.

Quinoa seeds can be used as an alternative bakery ingredient to improve the nutritional value of bakery products. Partial replacement of wheat flour with whole-quinoa-seed flour can produce dough with enhanced nutritional properties, since quinoa seeds have a higher protein content, a more balanced amino acid composition, and a higher content of dietary fibers and phytochemicals. The exceptionally lower gluten protein proportion and reduced starch digestibility make quinoa seeds as a potential material for the development of gluten-free bakery products or foods with low GI that are beneficial for customer health and wellness. The addition of quinoa seed flour into wheat flour produced weaker doughs, and the starch digestibility of bread with quinoa seed flour incorporated was reduced, which was associated with the inhibited digestive enzyme activity in the presence of the polyphenols and dietary fibers in quinoa seed flour [99,100]. Similar results were also noted: that the incorporation of quinoa seed flour contributed to a slower digestion rate of rapidly digested starch and reduced digestion extent of slowly digested fractions [4].

When incorporating quinoa seeds into food processing, it is critical to consider the physical properties and accessibility of the final products. Water-related characteristics, including water absorption, solubility, and swelling ability, are very important indices for evaluating the overall quality of quinoa seed-based products. Moreover, both the smaller granular size and lower content of amylose in quinoa seed starch, as well as the higher level of amphiphilic protein in quinoa seed flour, resulted in higher water absorption capacity and swelling power, and therefore exerted a positive influence on the quality of quinoa–wheat complex products [1,5,24]. The dough formed with the incorporation of quinoa seed flour caused different physical and textural properties compared to wheat flour dough, and resulted in baked products with lower loaf volumes, higher firmness, and denser structures. A previous study found that the addition of 25% quinoa seed flour into wheat flour did not reduce the acceptability of the bread; moreover, a more desirable flavor was denoted [101].

It should be mentioned that quinoa seed flour incorporated into bakery products tends to have decreased specific volume and increased hardness [102,103]. Previous research has indicated that quinoa seed starch has a good air incorporation ability during dough mixing, but the gas retention capability was greatly diminished during baking process [104]. Fermented cereals play a positive role in the organoleptic, nutritional, and shelf-life properties of bakery products [105,106]. Adding fermented quinoa seed flour into bread dough could increase the specific volume and, thus, decrease the crumbliness in comparison with dough made with unfermented flour [107]. A replacement of rice flour and potato starch with quinoa seed flour resulted in significantly reduced hardness and slightly improved springiness of cakes. The study suggested that a 50% quinoa seed flour formulation was favorable for better sensory quality of the final products [108]. The decrease in hardness in quinoa seed-based bakery foods because of the higher levels of fat and dietary fiber and the lack of gluten in quinoa seeds was favorable for the formation of soft and tender dough; however, inconsistent observations have been demonstrated elsewhere [102].

It could be concluded that the addition of quinoa seed flour into dough formulations has different influences on the textural properties and overall accessibility of the cooked products, which may be the result of the different reference samples chosen for the product. In comparison with the wheat flour-based products, increasing the amount of quinoa flour caused an increase in hardness. In cases of corn or rice-based snack foods, the addition of quinoa seed flour enhanced the tenderness of the final products. A previous study indicated that quinoa seed starch, characterized by smaller starch granules and lower amylose content, had higher enzymatic susceptibility, and amylase and proteinase might play a positive role to obtain increased volume in gluten-free products [109,110]. A gluten-free bread formulated with 50% quinoa seed flour, 38% corn/potato starch, and 15% whey protein isolate/sodium caseinate was produced with significantly increased specific volume. Similar results demonstrated that the tomographic attributes, such as the pore-sized distribution and wall thickness surrounding the pores, were associated with the hardness of extruded cereal-based snacks [103].

The exploration of plant-based meat products to replace meat sources is currently gaining remarkably increasing interest because of the appeal of human health maintenance, environmental protection, and sustainability. In case of their complete nutrient profile and bioactive properties, quinoa seeds have been incorporated into meat products either as ingredients or as fat alternatives [111]. Quinoa seed flour and quinoa seed starch have been added into the meat formula to improve the quality of the final meat product based on a health point view. Applications of quinoa seed flour commonly use at concentrations of less than 15%. One study found that quinoa seed flour has no negative effects on the physicochemical, textural, or sensory properties of the meat products; additionally, a specific amount of quinoa seed flour incorporated into the products induced improved oxidative stability [112,113,114]. Felix et al. [115] studied the effects of concentration and temperature on the rheological properties of quinoa seed flour-based gels, and it was indicated that quinoa seed flour in excess of 200 g/kg would facilitate the formation of gels with sausage-like textures, which might have potential in the design of meat-free products catering to vegan diets [115]. Quinoa seeds and starch have been formulated as ingredients to prepare chicken meatballs. Quinoa seed starch was more effective in hindering water loss during cooking and repeated freeze–thaw processes, and the best acceptability was observed with the quinoa seed-starch co-incorporated products [116]. In addition, compared with quinoa seed flour, the patties with the addition of quinoa seeds had lower cooking yields, attributed to the difficulty which quinoa seed components have in interacting with the meat matrix [6].

Plant-based food development has received rising interest within recent decades. The plant-based food market has become one of the fastest-growing sectors of the modern food industry. The revenue from plant-based protein is predicted to reach over USD 35 by 2024. Plant milk is regarded as a prevalent cow milk alternative. Among plant milk, soy milk is the most popular due to its higher protein content. However, the presence of undesirable components may limit its wide consumption [117]. Despite the lower allergenic capacities of rice milk, the lower protein content and unbalanced amino acid constitution do not make it fully nutritional options [118]. Quinoa seeds have a relatively high protein content, and quinoa protein contains higher ratios of lysine (2.4–7.8 g/100 g protein), methionine (0.3–9.1 g/100 g protein), and threonine (2.1–8.9 g/100 g protein), which are generally the limitations of amino acids in cereals [12]. A previous study indicated that the GI of quinoa seed milk was at a significantly lower level than that of rice milk (52 vs. 79), suggesting that quinoa seeds might be a raw material able to satisfy sensory quality requirements [119].

As documented in the Food and Agriculture Organization of the UN, quinoa seeds have been listed as one of the most popular pseudocereals for brewing. Un-malted quinoa seed and quinoa flakes are employed for brewing beer. Research results have shown that, despite the reduced soluble nitrogen content, the foam stability was significantly higher with 30% quinoa seed flakes, which can be explained by that fact that the higher levels of soluble proteins in quinoa seeds generate high molecular nitrogenous components. When quinoa seed flakes are incorporated in beer, they contribute to a higher sensory desirability than all-malt beer [120].

The potential of quinoa seed protein for wine phenolic fining was evaluated by Pino-Ramos et al. [121]. Compared to commercial fining agents, quinoa seed protein at the concentration of 30 g/hL or 50 g/hL had a similar efficacy in reducing the turbidity of red wines. The study suggested that quinoa seed protein may act as an alternative to animal protein in the wine fining process.

The construction of biopolymer-based systems for delivering functional ingredients is intended to improve their solubility, stability, bioaccessibility, and bioavailability, and has become one of the most recent research hotspots. A wide range of proteins and polysaccharides have been reported to play critical roles in this issue because of their biodegradability and biocompatibility. Quinoa seed proteins could form nano-micelles as delivery carriers for hydrophobic compounds by forming amorphous complexes. The encapsulation efficiency and loading capacity of quercetin amounted to 81.3% and 33.9%, respectively. Moreover, the system provided the hydrophobic agents with high retention after 3 months of storage [122]. The distinct characteristics of quinoa seed starch, with their smaller granular size and comparatively higher amount of amylopectin unit chains, allowed it to form a physical barrier for stabilizing emulsion droplets [123]. Quinoa seed starch nanoparticles exerted higher efficiency than maize starch nanoparticles in terms of loading quercetin, which was attributed to the lower crystallinity induced by the high amylopectin content in quinoa seeds, resulting in a higher quercetin adsorption. The stability of quercetin was significantly enhanced, and the incorporation of quercetin significantly delayed the enzymatic hydrolysis of starch nanoparticles [124]. Similar results were observed in rutin-loaded starch nanoparticles with enhanced encapsulation efficiency and loading capacity compared to maize starch nanoparticles [125]. Moreover, the octenyl succinic anhydride-modified quinoa seed starch showed an even better entrapping ability. The encapsulation efficiency of rutin-loaded Pickering emulsions stabilized by amphiphilic quinoa starch reached as high as 99.3%, and sustained release was achieved in the in vitro studies [126]. Previous studies have indicated that microspheres with high adsorption capacity could be fabricated from quinoa seed starch, and could act as a promising material for drug delivery [127].

Quinoa seeds are potential alternative film materials contributing to the dedication to environmental friendliness and development of new food products. Mixed films incorporating quinoa seed protein isolate combined together with chitosan showed enhanced mechanical properties compared with chitosan films, indicating a synergistic effect of the two biopolymers [128]. Previous studies have reported that native quinoa seed starch could be used to prepare transparent biodegradable films [129], whereas many kinds of botanical starches generally require modification for their applications.