## 1 Introduction  
Most conventional doughs and breads are produced using wheat flour, water, salt and yeast (brewer's yeast or sourdough starter) [1]. Breads rely on the unique ability of hydrated gluten to develop a viscoelastic network [2], which traps gas, and produces bread with higher loaf volume [3]. After baking, gluten contributes to moisture control [3]. Factors such as: the correct management of agronomical treatments in the field [4, 5], the milling method [6, 7, 8]; conditioning wheat to optimal moisture content before milling [9, 10]; and optimizing dough kneading [11, 12] all influence wheat flour quality, dough rheology, and bread characteristics and, at the same time, gluten quality, quantity, and strength. However, gluten is not the only important contributor to wheat dough and bread: starch also plays an important role. Starch granules are dispersed within a continuous network made up of gluten proteins [11, 12]. Nonetheless, it should be noted that, although starch dominates in quantity, the gluten network is mainly responsible for the overall, viscoelastic properties of dough [11]. Gluten intolerance, which leads to celiac disease and other health issues [3; 13], has become a worldwide problem. Consequently, interest in gluten-free products has grown among both researchers and consumers [3]. At the same time, so-called 'free-from' products (lactose-free, sugar-free, etc.) have become a global indicator of healthy lifestyle choices, which has expanded the market for gluten-free products [3]. These trends have led to a significant increase in demand, which the food industry has struggled to respond to. The main problem is that it is impossible to produce gluten-free doughs, breads, and bakery products with the same technological and sensorial performance as wheat-based products. In practice, making bread without gluten is a major challenge for researchers, bakers, and the food industry. The absence of gluten has a significant effect on both dough rheology and the quality of the final product [13; 14; 15]. Gluten-free doughs are characterized by lower cohesiveness and elasticity compared to wheat dough [13; 14; 15]. Moreover, the lack of gluten results in bread with a poor texture and color, characterized by lower specific volume [13; 14; 15]. Other problems are a shorter shelf life, dry mouth feeling, unsatisfying taste, and other unwanted features [13; 14; 15]. Gluten-free doughs and breads are not only consumed by those who are gluten intolerant, or people with celiac disease, they are also part of a market towards environmental sustainability [16]. Notwithstanding the efforts made by bakers, scientists, and the food industry, the manufacture of gluten-free baked products continues to present a significant technological challenge. This point is illustrated by the gluten-free breads that are currently available. Although demand is constantly growing, the majority of commercial, gluten-free products are of very poor technological and sensorial quality [3; 13; 14; 15; 17]. The literature proposes various improvement strategies. Most focus on ingredients, additives, enzymes, and other substances (or combinations of them) that are able to reproduce the viscoelastic properties of the gluten network, and improve the final product from a technological and sensorial point of view. Starch is one of the most important constituents, highlighted by the copious number of articles on this topic. Other essential elements are water addition and the capacity to absorb water [3]. Water content is critical, as it influences loaf quality, texture, taste, smell, volume, flavor, and mouthfeel, and various studies have highlighted the influence of water mobility and distribution on dough rheology and baking performance [3; 14; 15; 17]. However, there is a lack of an overview that summarizes the characteristics of gluten-free products, and the most interesting improvement approaches. Therefore, the first aim of this paper is to review current knowledge regarding gluten-free doughs, breads, and bakery products.