# Nutritional and Functional Properties of Gluten-Free Flours
## 3 Results  
### Proximate Composition of GF Flours  
The gluten content (expressed in ppm) for the flours under investigation was as follows: 14.15 (rice), 8.63 (brown rice), 7.22 (maize), 6.14 (oat), 8.75 (millet), 8.42 (teff), 5.3 (amaranth), 3.94 (buckwheat), 8.04 (quinoa), 4.66 (chickpea), 2.02 (gram), 4.78 (tiger nut), and 3.68 (plantain). All the flours had a gluten content lower than 20 ppm, which confirms their claim as gluten-free. The proximate composition of the analyzed gluten-free flour is presented in Table 1. Among the different GF flours, protein content was significantly higher (_p_ < 0.05) in both chickpea samples and decreased in the order: gram > chickpea > amaranth > buckwheat > quinoa > teff > oat > millet > brown rice > rice > maize > tiger nut > plantain. Proteincontent of gram flour was about 1.27 times the chicken level. Compared to the rice flour--the most used GF flour--the protein content in gram was 8.2-fold higher. The protein content varies between varieties. For example, millet recorded different protein values depending on the type: 11.9% for common millet flour, 8% for pearl millet flour, and 7.3% for finger millet flour [28; 29]. In addition, the protein content varies from 5.7-14.2% for buckwheat, 9.1-16.7% for quinoa, and 13.1-21.5% for amaranth [30; 31; 32]. The fat content was relatively high in tiger nut flour (25.1%) when compared to the other flours, which might have a negative impact on the shelf-life and quality characteristics of the foods. Further, it varied from 6.11% for gram flour to 0.34% for plantain flour. The higher fat content of the flours leads to their ability to absorb and retain oil, improves the structure and mouth feel, and helps to enhance the flavor retention, also reducing moisture and fat losses of food products [33]. The ash content varied from about 0.6% (rice and maize flours) to 3.5% (chickpea flour). The high ash content (>2%) for chickpea, teff, amaranth, quinoa, tiger nut, buckwheat, and plantain flours denoted that these types of GF flours are an important source of minerals. The highest levels of dietary fiber (\(p<0.05\)) were found for tiger nut, chickpea, and buckwheat flours, while the rice flour had the lowest content (0.88%). The fiber content of tiger nut flour (35.4%) was much higher compared to the values reported in other studies, which varied between 5.6-22.3% [34; 35; 36]. This variance comes from the difference in varieties along with the milling procedure or environmental factors. Rice, plantain, and brown rice had higher starch content (76.2-82.6%) than those of amaranth, gram, chickpea, and tiger nut flours (<60%) (\(p<0.05\)). Amylose content ranged between 6.5-8.4% and 30.1% starch corresponding to amaranth and quinoa flour for the lowest content and tiger nut for the highest content, respectively. Brown rice had a lower amylose content than rice flour (\(p<0.05\)). As shown in Table 1, the percentage of amylose from the total starch was relatively similar with no significant difference (\(p>0.05\)) between several groups of GF flours, mainly: (1) teff, buckwheat, and chickpea (28-28.7%); (2) millet, rice, and maize (24-25.3%); and (3) maize, gram, plantain, and oat (22.1-24%). The ratio between amylose and amylopectin has an impact on the starch digestion and, accordingly, to the glycemic index. [PERSON] et al. [37] showed a slight negative correlation (r = \(-0.368\)) between amylose content and predicted glycemic index in gluten-free cereals, pseudo-cereal, and legumes flours. Regarding the bread products, a much higher negative correlation was obtained (r = \(-0.964\)) [38]. Thus, the lower amylose content in quinoa (5.3%) led to a high glycemic index of quinoa bread, while a lower glycemic index was obtained when flours with higher amylose content (20.5-22.8%), such as oat and teff were used in the bread manufacture. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Flours** & **Moisture, \%** & **Protein, \% d.m. ** & **Fat, \% d.m. ** & **Ash, \% d.m. ** & **Fiber, \% d.m. ** & **Starch, \% d.m.