*3.1. Proximate Composition of Flours*

The proximate composition of quinoa, millet, sorghum and rice whole flours is shown in Table 1. The highest proteins content of 14.05% was registered for quinoa flour. According to Basile et al. [4], quinoa has a similar protein content with the highest strains of wheat, with lower amounts of glutinous proteins. In addition, quinoa was reported as a source of complete protein, having a well-balanced amino acids composition needed for human diet, having high contents of methionine and lysine [6]. Moreover, Vega-Galvez et al. [6] noted that the value of quinoa protein is similar to casein in milk. According to Srichuwong et al. [8] the percentage of lysine in the quinoa proteins is 6.9%, much higher than in sorghum (2.2%), millet (3.1%) or wheat (2.9%). Regarding the methionine content of the total proteins from quinoa, millet and sorghum, the percentages are in the 2.5–3.6% range, significantly higher compared to wheat proteins which have 1.8% [8]. Fairbanks et al. [27] appreciated that the high level of lysine from quinoa proteins is due to the high amount of albumins and globulins which are rich in this amino acid.


**Table 1.** Proximate compositions of whole quinoa, sorghum, millet and rice flours (% d.w.).

The proteins content of sorghum whole flour was 10.29%, close to the results reported by Khan et al. [14] for red sorghum whole flour (10.05%) and white sorghum whole flour (11.77%). Mokrane et al. [28] analyzed the sorghum protein quality, and observed the high amino acid scores that varied between 0.9 and 2.6, except for lysine, methionine and cysteine. The sorghum proteins include albumins, globulins, kafirins, cross-linked kafirins and glutelins, among which the kafirins represent about 80% of decorticated flour protein [29].

In case of millet, the proteins content was 11.01%, comparable to the value of 10.75% reported by USDA [30]. According to Devi et al. [31], different millet species present large variations of proteins content, ranging from 7.3–8.3% in case of finger and kodo millet, to 14.5% in case of pearl millet; the proso and foxtail millet have protein contents of 11–11.3%. Kalinova and Moudry [32] reported for proso millet proteins an essential amino acid index of 0.51, and the amino acids scores of 0.47 for lysine, of 0.78 for tyrosine and of 0.75 of cysteine and methionine.

Among the investigated whole protein flours, the smallest proteins content of 6.18% was registered for rice flour (Table 1), lower compared to the results of 7.23% reported by USDA [30], or 7.5% by Devi et al. [31].

The results shown in Table 1 indicated that the fat content varied from 5.29%, for quinoa flour, to 2.16%, for rice flour. Higher fat contents of 6.0, 6.4 and 6.8% were reported by Pereira et al. [10] for whole quinoa white grain, red grain and black grain, respectively. On the other hand, Vidueiros et al. [11] reported lower fat content of 4.7–5.3% for different varieties of quinoa. Sorghum and millet flours presented fat contents of 3.17 and 3.91%, respectively, while Srichuwong et al. [8] reported values of 5 and 3.7%, in case of white and red sorghum, and 4.1% for millet flour. The fat content of rice whole flour was 2.16%.

The lipids are divided into free and bound fractions, the free lipids being the most present fractions [6]. Ragaee et al. [16] reported the presence of free lipid fractions of 2.0–4.1 and 5.6%, and of 0.1–0.56 and 0.6–0.9% for bound fractions in sorghum and millet, respectively. In case of quinoa flour, Collar and Angioloni [6] reported for free and bound lipids fractions values of 3.23 and 0.28 g/100 g flour, respectively.

The lipid composition of quinoa stands out in the relation to the rest of cereals analyzed, through the fatty acid profile that is comparable to that of corn and soybeans [9]. The major saturated fatty acid is palmitic acid (about 10%), while the oleic, linoleic and alpha-linolenic acids represents about 19.7–29.5, 49–56.4 and 8.7–11.7%, respectively [8–10]. According to Rooney [33], when compared to quinoa, the sorghum and millet grains contain higher levels of palmitic acid (of 12 and 20%, respectively), oleic acid (34 and 26%, respectively), and lower levels of linoleic acid (of 50 and 45%, respectively), and linolenic acid (of 3 and 4%, respectively).

The ash content of millet (2.7%) and quinoa (2.39%) flours is higher compared to rice and sorghum flours that had values of 1.53 and 1.61%, respectively (Table 1). The ash content of quinoa flour used in the present study is lower than that reported by other authors [11], probably due the intensity of the washing process of grains. On the other hand, in case of rice flour the ash content was higher than that reported by other authors [34]. Instead, in case of sorghum and millet our results were between the values reported by other authors, namely 2–3.6% [31] and 1.52–2.57% [14], respectively.

The highest amounts of total dietary fibers were registered in case of quinoa and millet flours, of 9.11 and 8.57%, respectively, whereas the rice flour had the lowest total dietary fiber content (4.69%) among the investigated grains. The soluble fiber content ranged between 2.36, in quinoa flour, and 0.90% in sorghum flour. The insoluble fiber content decreased in the following order: millet (7.46%), quinoa (6.74%), sorghum (6.52%) and rice (3.72%) flours. The results reported by different authors present a large variation, even if the same method used for investigations. For instance, Srichuwong et al. [8] reported much lower value for total fiber content for quinoa and millet (9.5% and 8.4–10%, respectively), compared to the Kurek et al. [35] (16.43% and 11.71%, respectively), even if the authors used the same method. These results highlight the great variability in terms of chemical composition among grain varieties.

Regarding fiber compositions, Lamothe et al. [36] reported that, in case of quinoa, the soluble and insoluble dietary fiber were composed mainly of pectic polysaccharides and xyloglucans, unlike cereals that contain mostly arabinoxylans. Lai et al. [37] reported that the total dietary fiber extracted from nonwaxy brown rice contained important amount of pectic substances, whereas the waxy counterparts were richer in hemicellulose or cellulose.

Due to the high contents of protein, fiber, fat and ash from quinoa, sorghum and millet flours, the amount of starch present in the samples was lower compared to the rice flour (Table 1). The lowest starch content was registered in case of quinoa flour (58.84%), followed by millet and sorghum flours, while the highest value was obtained for rice flour (74.09%). The amylose content in starch varied from 17.76 for quinoa to 23.23% for sorghum flours. Navruz-Varli and Sanlier [9] showed that the amylose content in the quinoa starch can vary from 3 to 22%, being lower than in wheat. The amylose content of rice starch depends by type of rice. Thus, Chung et al. [38] reported value of 27.2% of the amylose content for the rice starch isolated from long grains, and significantly lower values of 15.4 and 18.8% for the amylose contents for the rice starches isolated from medium and round grains, respectively. Srichuwong et al. [8] reported for millet and sorghum starches values of amylose about of 24 and 24.6–25.8%, respectively.

#### *3.2. Physical Properties of Flours*

The granularity of the flour samples is an important physical parameter because of the high influence on the quality of the bakery products. The granularity of the flours was estimated by determining the tailing and sieve fractions on a set of sieves with mesh aperture ranging from 500 to 125 μm, and the fineness modulus.

The sorghum and millet flours had highest percentage of particles with size between 125 and 315 μm, of 80.7 and 74.9%, respectively (Table 2). In case of rice flour highest percentage of particles had larger size, ranging between 315 and 500 μm, while in case of quinoa flour the particles size was most homogenous, even if the percentage of particles with size between 125 and 315 μm was about two times higher than of those between 315 and 500 μm, and three times higher than of those with size less than 125 μm. The higher percentage of larger particles in case of rice flour resulted in higher fineness module (of 2.85) compared to the rest of flours. Sorghum flour had the lowest percentage of particles higher than 315 μm and the lowest fineness module of 1.63.

The fineness module is a measure of the distribution of fine and coarse particles in the analyzed sample, and can be influenced on one hand by grains related factors such as compactness of the endosperm, composition and texture of the pericarp and embryo, and by the milling method on the other hand. Taking into account that sorghum, millet and rice flours are commercial flours, it was not possible to factor the effect of grinding on the particle size distribution. Anyway, the difference between the values of the fineness modulus of the investigated flour might be due to the differences in terms of compactness of the rice endosperm.


**Table 2.** Physical properties of whole quinoa, sorghum, millet and rice flours.

The starch damaged of sorghum flour (8.17%) was higher than other flours (3.85–4.44%) (Table 2). A positive correlation of 0.87 was registered between the fineness module and damaged starch (*p* < 0.05).

The color parameters of the investigated flours are presented in Table 2. The lowest lightness values (L\*) were obtained in case of quinoa and sorghum flours. Sorghum flour presented the highest value of redness (a\*) and lowest values of yellowness (b\*), chroma (C\*) and hue angle (h◦), and most probably these values might be explained by the presence of colored polyphenolics such as tannins and anthocyanins [17]. On the other hand, the higher values of yellowness (b\*) registered in case of quinoa, millet and rice flour might be explained by the presence of carotenoids in these samples [39].
