# Effect of Citrus Fiber on the Rheological Properties of Dough and Quality of the Gluten-Free Bread
## 1 Introduction  
The occurrence of common diet-related diseases is often triggered by improper lifestyle and nutrition. A number of problems could be caused by diets rich in highly refined products and deprived of low processed plant foods containing high levels of dietary fiber [1]. The consumption of foods rich in dietary fiber is insufficient, hence there is a need to enrich food, including bread, with fiber preparations of various origin [2]. Fiber preparations, used in the production of functional food, apart from their beneficial effect on the human body, positively impact the texture, sensory and functional characteristics of the products [3]. Properties of gluten-free bread, in which starch is the major component, are predominantly determined by characteristics of this polymer [4, 5]. Consequently, the nutritional value of such products is relatively low. The studies performed in vitro on resistant starch present in gluten-free bread by [PERSON] and [PERSON] [6] showed that the main fraction of starch is rapidly digested (92.5%), which corresponds to a glycaemic index up to 96. On the other hand, the results of [PERSON] and co-workers [7] indicated that the intake of fiber with a gluten-free diet is low, while simple sugars are present in large quantities. Therefore the application of naturally gluten-free components, e.g.,pseudocereals rich in dietary fiber, as well as the use of fiber preparations produced from various raw materials may significantly increase the consumption of fiber by celiacs. Studies on the influence of fiber-rich ingredients or preparations on the structure and properties of gluten-free dough and bread are quite widely described in the literature. This is due, on the one hand, to the very broad range of ingredients or preparations rich in fiber, and, on the other hand, to the variety of raw materials, recipes and technologies for obtaining gluten-free products [8; 9]. A natural way to increase the content of fiber in gluten-free bread is to introduce a suitable flour from gluten-free sources into the recipe. Such flours, depending on their origin, may contain significant amounts of dietary fiber and its individual fractions, and their use, in addition to improving nutritional value, may have a beneficial effect on the physicochemical characteristics and sensory qualities [10]. [PERSON] et al. [11], while examining the influence of acorn flour on the dough properties and characteristics of gluten-free starch based bread, concluded that apart from the nutritional effect, i.e., an increase in the content of particular nutrients, including dietary fiber, the additive could have a positive effect on the increase in bread volume and crumb structure, and furthermore limit its staling. In another study, it was observed that the presence of hemp flour in the recipe of gluten-free bread could significantly increase the content of dietary fiber and its fractions, and reduce crumb hardness and amylopectin recrystallization, limiting bread staling [12]. An elevated content of dietary fiber in dough and then in bread not only improves nutritional value, but also affects sensory and physicochemical properties, including water retention and rate of bread staling [13; 14; 15; 16; 17]. Fruit-derived dietary fiber is often considered as a potential ingredient of bakery products and has been intensively investigated [18]. The main benefits of citrus fiber in comparison to other sources is a higher level of soluble fractions, reaching up to 33% [19]. Bakery products enriched in citrus fiber include biscuits [20; 21], muffins [22; 23], and bread [24; 25], including gluten-free formulations based on rice flour with potato starch [26; 27] and corn starch with corn gluten meal [28]. Due to very diverse sources of fiber preparations and other ingredients of bread and the technology of its production, the influence of enriching gluten-free bread with dietary fiber is still problematic [29; 30].