# The Clean Label Concept: Novel Approaches in Gluten-Free Breadmaking
## 7 Use of Fiber  
Several studies have shown that the type and origin of fiber can affect not only the specific volume, apparent viscosity, and consistency of gluten-free dough, but also the sensory perception, shelf life, and texture of baked goods. The fiber length, degree of polymerization, soluble/insoluble fiber ratio, level of enrichment and the interaction of fiber with other ingredients are the key parameters [48; 49; 50; 51]. Various sources of fiber have been investigated, including by-products of milling and fruit processing, such as inulin [47; 50; 51; 52], apple [48; 53], maize [54], sugar beet [53; 55], oat fiber [47; 54], psyllium [48; 55], tomato [48], wheat [54], barley [54], pectin [52], soya [52], and lupin [52]. However, these fibers are treated as enrichment ingredients and not as structure-forming agents. The incorporation of fiber also has a beneficial impact on the nutritional properties of gluten-free baked goods. To limit its negative effects, the optimization of hydration is again essential. The addition of insoluble fibers with high water capacity can lead to an excessive bread hardness if an adequate amount of water is not incorporated into the formulation [47; 55; 56]. As a consequence of high water-binding capacity, oat \(\beta\)-d-glucan affects the ratio of the viscous portion of the batter to the elastic portion. The incorporation of inulin does not cause significant changes in the structure of the batter. The use of inulin affects crumb hardness and the rate of staling. Although \(\beta\)-d-glucan is partly degraded during bread production, [PERSON] et al. [47] recommended this fiber for increasing the nutritional value of gluten-free bread. According to [PERSON] and [PERSON] [48], the use of psyllium (addition level 5-10%) can have a very positive influence on crumb hardness. Crumb hardness fell by 52.5-67.0% in comparison to the reference bread on day 0, and by 37.4-57.7% on the fourth day of storage. Similar findings were reported for apple fiber. Crumb hardness was lowered by 30.5-64.2% on day 0 and by 13.8-51.0% after 4 days [48]. These results are similar to those reported in a study by [PERSON] et al. [55]. A more effective antistaling effect of psyllium vs. sugar beet fiber was observed after three days of storage, presumably due to the higher water binding capacity of psyllium. Another study has shown that apple fiber in comparison to sugar beet fiber was more efficient in terms of the improvement of gluten-free bread specific volume, crumb softness, and chewiness. Glut-free breads containing 4 g/100 g HPMC and 3, 5, 7 g/g sugar beet or apple fiber were rated as excellent by a sensory evaluation panel. They were characterized by an appealing crust and crumb color and a fine crumb texture. Proximate composition analysis results for gluten-free breads containing 3 and 7 g/100 g sugar beet or apple fiber show a nutritional profile similar to commercially available gluten-free breads fortified with fiber [53]. [PERSON] et al. [50] suggest that inulin-type fructans might be impacted by processing, depending on their degree of polymerization (DP). Low DP inulins are hydrolyzed to some extent during breadmaking, which affects both the final fiber content in the bread and its structuring potential. Therefore, special attention should be paid to the selection of the type of inulin. According to this research, it is also advisable to use yeast with low invertase activity to leaven inulin-containing gluten-free baked goods. Inulin overdose (10% content in the recipe) is necessary to obtain 3% fiber in the final baked goods [50].