## 3 Main Findings
### Ingredients and Their Effects on Gluten-Free Dough Rheology and Bread Quality
#### 3.3.2 Naturally Gluten-Free Sources of Starch  
Starch is the most important reserve polysaccharide, and the most abundant constituent in many plants [14]. It is a unique vegetal carbohydrate, as it is naturally present in the form of dense, and relatively-insoluble semi-crystalline granules [13; 14; 15; 17]. It plays multiple roles in food applications.  
In baked products, it influences dough rheology and extensibility, bread texture, and overall acceptance [13; 14; 15; 17].  
As reported in [PERSON] et al. (2008) [14], most starch granules are a mixture of amylose and amylopectin, and there are clear differences between the two. Amylose is a linear molecule, consisting of \(\varsigma\)-(1,4)-linked D-glucopyranosyl units with a degree of polymerization in the range of 500-600 glucose residues [14]. In contrast, amylopectin is a very large, highly-branched polysaccharide with a degree of polymerization ranging from \(3\times 10^{5}\) to \(3\times 10^{6}\) glucose units, and is composed of chains of \(\alpha\)-(1,4)-linked D-glucopyranosyl residues, which are interlinked by oL(1,6)-bonds [14]. The ratio between amylose and amylopectin differs significantly between different types of starches, ranging from 25-28% to 72-75%, respectively [13; 14; 15]. Botanically, starch takes the form of intracellular, water-insoluble granules of different sizes and shapes [13; 14; 15; 17].  
Many studies highlight that, during milling, a significant amount of starch is damaged [6; 7; 8; 10; 14; 17]. This mechanical damage has a significant impact on its properties; in particular, damaged starch has higher water absorption capacity, and is more susceptible to enzymatic hydrolysis [6; 7; 14]. Heating starch suspensions in water that is above a specific temperature leads to disruption at the molecular level, with a consequent loss of crystallinity, and irreversible granule swelling [14]. This process, called gelatinization, facilitates molecular mobility, the dissociation of amylopectin double helices, and the melting of crystallites [14; 15]. Gelatinization is also related to a reduction in starch solubilization (mainly amylose leaching) that determines an increase in the viscosity of the starch suspension [13; 14; 15; 17]. This phenomenon continues with further heating and, above the gelatinization temperature, a continuous phase of solubilized macromolecules (mainly amylose), and a discontinuous phase of swollen, amorphous starch granules (remnants) are formed [14].  
When starch is cooled after heating, another phenomenon, called retrogradation, occurs. Here, starch polysaccharides re-associate to form a more ordered, crystalline state [13; 14]. Significant differences in the kinetics of starch retrogradation have been reported for amylose and amylopectin [13; 14; 15; 17]. The re-crystallization of short amylopectin side-chains is significantly slower than amylose retrogradation, which is faster and determines, to a greater extent, the initial firmness of the starch gel [14; 15; 17]. Several factors have been found to influence retrogradation. The most noteworthy are related to the presence of other molecules, such as sugars, salts, lipids (in particular polar lipids), and pH [13; 14].  
There are several, naturally gluten-free sources of starch. They include rice, potatoes, tapioca, and cornstarch [14; 15]. Potato starch seems to be the most promising option, as it has desirable characteristics that differ significantly from the other sources. It has been reported that small amounts of potato solids help to maintain the freshness of bread, and impart a distinctive, pleasing flavor, improving tasting qualities [15]. However, the latter authors observe that dough made with potato starch is highly viscous, and susceptible to shear; moreover, big potato granules are susceptible to breakage. The study also notes that high-molecular-weight amylose, and phosphate groups esterified to amylopectin, contribute to the high transparency, swelling power, water binding capacity, and freeze-thaw stability of potato starches.