## 3 Results and Discussion
### Physicochemical Characteristics of GF Bread  
Table 5 shows the physicochemical results for bread formulation. Specific volume (SV) increased from the control bread to the 5% APP bread. Nevertheless, this increment did not show a linear tendency: the additions of larger amounts of APP (6-8%) decreased specific volume and gave lower values than GFB5. Similar results were reported by [PERSON] et al. [48], where the highest specific volumes of bread were described in breads with 10% fiber extract, whilst 15% and 20% addition showed lower values. [PERSON] et al. [49] described significantly higher values in fiber-supplemented GF samples compared to the control and increased SV values until 4% orange fiber addition, followed by lowered values from that level onwards. Moreover, results for specific volume in GFB were coherent with values compiled by [PERSON] et al. [31] for increasing APP addition. The specific volume of GFB has been reported to vary significantly in relation to the ingredients and bread making procedure [30]. In this work, results spanned between 2.4 and 3.1 cm\({}^{3}\)/g, in agreement with values reported for GFB based on rice flour and starches in previous studies [48; 49]. In addition to other factors (dough viscosity, active surface components), fiber content is highly related to alterations in specific volume, because of its high water binding capacity, which might limit fermentation and, thus, gas production. The absence of gluten complicates the retention of CO\({}_{2}\) created during fermentation and, according to [PERSON] et al. [31], high fiber ingredients (such as APP) can make this problem even more critical. In this study, the specific volume was acceptable for all the samples, even  
though it started to show a declining tendency (GFB6 and GFB8). This was due to the adaptation of water proportion, which tends to equilibrate excess of water absorption by fiber [31]. [PERSON] et al. [22] reported specific volumes lower than 2.16 cm\({}^{3}\)/g in bread formulations with 2.5 to 7.5% added. These values were obtained using an APP with lower fiber content (15.9%) than ours (80.4%). It is relevant to take into account specifically the type of ingredient that is being added, and its composition, so that it can be correlated to the final quality characteristics. The type of fiber will depend on the source (variety of fruit or cereal) as concluded in previous research [7].  
The moisture of the GFB did not differ generally among formulations (Table 5), apart from GFB5. As a greater water amount was added in APP-containing samples, GFB5 had the highest moisture values, similarly to previous results described in the literature [4]. However, further addition of APP decreased water content and aw, as has been observed before [50]. Our results suggested a decrease in available water from GFB5 to GFB8, which can be explained by the fact that increasing fiber content enhances the capacity to trap water present in the food matrix.  
Antioxidant activity is shown in Table 5, expressed either as percentage or as DPPH equivalents. The literature shows that the antioxidant activity of GFB is negatively affected by bread making [51]. In our study, control breads presented lower antioxidant values, and while additions at 5% and 6% did not differ significantly, 8% additions did. Consequently, and in spite of the losses that bread making provokes, APP addition increased the antioxidant activity of breads, which matches other previous studies [52]. [PERSON] et al. [23] also described increased antioxidant activity in GF breads with 5 to 15% APP added.