**Iuliana Banu and Iuliana Aprodu \***

Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, 111 Domneasca Str., 800201 Galati, Romania; iuliana.banu@ugal.ro

**\*** Correspondence: iuliana.aprodu@ugal.ro

Received: 19 November 2020; Accepted: 7 December 2020; Published: 8 December 2020

**Abstract:** A comparative analysis of quinoa, sorghum, millet and rice flours and breads in terms of proximate composition, resistant starch, antioxidant activity and total phenolic content was realized in this study. Quinoa whole flour had the highest content of proteins, fat, ash and total dietary fiber, followed by millet and sorghum flours. Quinoa and rice breads had higher specific volume (192.22 and 181.04 cm3/100 g, respectively) and lower crumb firmness (10.81 and 13.74 N, respectively) compared to sorghum and millet breads. The highest total phenol content was obtained in the case of bread prepared with quinoa flour (398.42 mg ferulic acid equiv/100 g d.w.), while the lowest content was obtained for the rice flour bread (70.34 mg ferulic acid equiv/100 g d.w). The antioxidant activity of gluten-free breads decreased in the following order: sorghum > quinoa > millet > rice. Quinoa bread had the highest resistant starch content of 3.28% d.w., while the rice bread had the highest digestible starch content of 81.48% d.w. The slowly digestible starch varied from 15.5% d.w. for quinoa bread, to 6.51% d.w. for millet bread. These results revealed the huge potential of quinoa, sorghum and millet to be used for developing functional gluten-free bread.

**Keywords:** quinoa; millet; sorghum; rice; gluten-free bread

#### **1. Introduction**

Coeliac disease is a lifelong autoimmune enteropathy induced by gluten consumption, affecting persons which are genetically susceptible. Due to the increasing prevalence worldwide, the coeliac disease started to be considered a major public health problem [1]. Taking into account that no efficient cure was reported yet for this condition, avoidance of gluten-containing products in the diet was recommend as the main solution. Therefore, identifying ingredients and tools for obtaining high-quality gluten-free products is highly desired. Rice flour is considered the most important ingredient in gluten-free bread making, but in the last period the minor grains like millet, sorghum and quinoa became increasingly important for producing gluten-free baking products [2].

Originating from South America but with a great adaptability to different growing conditions, quinoa has become more and more popular due to the well-balanced nutritional composition [3–5]. Quinoa is recommended primarily by the content and quality of its proteins, being rich in amino acids which are deficient in cereals. In fact, the amino acids composition of quinoa proteins is close to the ideal protein recommended by FAO [3,6–8]. In addition, quinoa contains high levels of unsaturated fatty acids [9–11], vitamins [9], minerals [12], dietary fiber and polyphenols [13].

Sorghum and millet are two cereals which are insufficiently used in bakery products, even if they have nutritional compositions comparable to other cereals [14], and could be used if not as the based flour, at least as functional ingredients, mainly due to phenolic compounds [2,15,16] and resistant starch contents [14,17]. Moreover, the two cereals can be grown on semi-arid regions, where other cereals do not give consistent productions.

Several studies pointed out that quinoa, sorghum and millet have huge potential to be used for developing functional foods, due to the high level of phenolic compounds, antioxidant capacity and low starch digestibility [2,3,17].

The objective of this study was to compare quinoa, sorghum, millet and rice in terms of composition, bread-making potential and physical properties, resistant starch, antioxidant activity and total phenolic content of breads. The rice was included in this study due the large applications in gluten-free bread making.
