## 4 Discussion
### Strategies to Improve Gluten-Free Dough Rheology and Bread Characteristics
#### 4.1.7 Alternative Sources of Protein, and Functionalized Zein  
As noted in Section 3.3.3, several authors have tested the addition of conventional protein from vegetal (soya, potato, etc.) and animal (egg album, dairy products, etc.) sources to improve dough rheology and bread characteristics, with interesting results [41; 42; 43; 44]. Three studies have reported that best results are obtained for egg albumen proteins [42; 43; 44]. Legumes are another interesting source of protein that has been widely examined in the literature. One study highlighted that the addition of lupin and pea protein isolates improved dough rheology, increased loaf volume, cell pores, and led to a softer crumb [45]. Lupine protein was assessed in [PERSON] and [PERSON] (2015) [13], and was found to decrease crumb hardness and slightly increase the storage modulus. However, it seems that chickpea is the best improper. An early study found that the addition of 5% chickpea flour significantly improved ancient wheat flour, notably with respect to increased dough stability and bread volume [20]. Chickpeas have also proven to be able to improve gluten-free doughs and bread. In [PERSON] et al. (2012) [46], the authors compared the effects of the addition of chickpea flour, pea isolate, carob germ flour, and soya flour, and found that chickpea bread had the highest volume (3.26 cm\({}^{3}\)/g), and the softest crumb. These findings are in accordance with [PERSON] et al. (2018) [47], who tested the effects of raw, roasted, and dehulled chickpea flours on gluten-free formulations based on rice flour (75%) and chickpea (25%). Doughs containing chickpea flours had higher protein and fat content, reduced retrogradation tendency, higher foaming capacity, superior dough stability, and higher CO\({}_{2}\) retention capacity (\(\geq\)98%). At the same time, chickpea roasting decreased foaming capacity, and stability. Both the food industry and consumers are increasingly sensitive to environmental impacts. This has led to an ongoing search for alternative, cheaper and more sustainable sources of protein. In this context, insects seem to be one of the best opportunities [18; 20]. A recent study by [PERSON] et al. (2019) [48] tested gluten-free formulations substituted with cricket flour at 2%, 6% and 10%. Although little change was observed for dough rheology, breads were characterized by significantly reduced hardness, and improved consistency and texture. The authors also suggested that its use could significantly improve the nutritional content of gluten-free products. Another interesting approach is to functionalize non-gluten proteins, in particular, zein. Zein is an alcohol-soluble protein made from corn. It is classified as a prolamin, and composed of a combination of peptide chains linked by disulfide bonds [49]. Above its glass transition temperature (35-40 \({}^{\circ}\)C), and combined with other dough components, its molecular structures are able to form doughs with viscoelastic properties comparable to those of gluten. It has been commercially available for about 60 years, and already has several applications, including the production of fibers, adhesives, buttons, binders, and coatings [49]. As the United States Food and Drug Administration has recently confirmed that it is suitable for use in the food industry, there has been an explosion of interest in its unique characteristics and functionalities (which are similar to those of gluten) [49]. In a detailed study, [PERSON] et al. (2012) [50] suggested that the properties of functionalized zein are the result of developing fibrous, b-sheet-rich protein networks. A later study investigated the optimal extrusion temperature for zein in rice-based formulations [51]. The authors highlighted that the correct temperature resulted in doughs with viscoelastic properties similar to those of doughs prepared with wheat flours. Extrusion conditions also influenced dough elasticity, with the greatest effect seen at 160 \({}^{\circ}\)C [51].