## 3 Results and Discussion
### Physical, Structural, and Textual Properties of Shorthead Biscuits
Both the addition of fibres and the replacement of sucrose with other sweeteners led to statistically significant increases in density and decreases in porosity. The actual density of the cakes was not significantly different (\(p=0.081\)). Similar effects of soluble fibres (Nutriose and polydextrose) on density and porosity were observed in gluten-free bread [19]. Replacing sucrose with maltitol did not affect apparent density, but the use of Tagatesse and erythroid-stevia, in combination with both fibres, increased apparent density. The effects of fibre, sweetener, and the interaction of these factors on apparent density and porosity were demonstrated. Among the biscuits with both wheat and oat fibre, those with sucrose and maltitol had the highest porosity, while those with Tagatesse and erythroid-stevia had the lowest. At the same time, biscuits with wheat fibre and the tested sweeteners exhibited significantly higher porosity than those with oat fibre. The biscuits exhibited a variety of structural characteristics. Example images of the internal structure are provided in Figure S1 (Supplementary Materials). Variations were observed in the shape and distribution of the pores. All the biscuits studied displayed a porous structure with numerous irregularly shaped pores. These observations were further confirmed by calculations. While the average pore area size in the biscuits did not show significant differences (Table 3), the cumulative pore size distribution, shown in Figure S2 (Supplementary Materials), indicates that the addition of fibre and the replacement of sucrose with alternative sweeteners resulted in differences in pore size. The shape factor of the pores in the biscuits ranged from 0.539 to 0.619, indicating that the pores were not round in shape. The addition of fibres and sweeteners contributed to a reduction in this parameter (Table 3). The type of fibre did not affect the pore elongation factor, but the type of sweetener had a significant impact (Table 3, Figure S3). In addition, an interaction between the sweetener and fibre was observed. The use of sweeteners with wheat fibre resulted in lower values for the pore elongation factor compared to oat fibre (Table 3). The fracture properties are closely related to the degree of inhomogeneity in the material, with greater structural inhomogeneity resulting in lower fracture stress [43]. This observation aligns with the correlations obtained in our study. The inhomogeneity of the structure (shape factor, elongation factor) and reduced porosity, resulting from the addition of fibres and the replacement of sucrose with sweeteners, led to a decrease in fracturability (Table 4). In biscuits containing sucrose, the addition of wheat fibre significantly reduced hardness, while oat fibre had no effect (Table 4). An interaction between the sweeteners and fibres was observed. Tagatesse and maltitol, when combined with wheat fibre, caused a significant increase in biscuit hardness (Table 4), whereas sweeteners combined with oat fibre had no effect on hardness (Table 4). Similarly, [PERSON] et al. [21] showed that replacing 10% of the flour with a hydrocolloid containing 20% \(\beta\)-glucan had no effect on biscuit hardness. [PERSON] et al. [44] demonstrated that the molecular weight of \(\beta\)-glucan is important; adding \(\beta\)-glucan of varying molecular weights to a muffin recipe increased hardness and decreased springiness. During baking, the texture formation of cakes is strongly influenced by the thermosetting of gluten. This relationship, demonstrated by [PERSON] et al. [45], was confirmed by [PERSON] et al. [9]. In addition, [PERSON] et al. [9] proved that redox factors modulate gluten aggregation during biscuit baking, affecting the dimensions, internal structure, and texture of the biscuits. The low water content, along with high sugar and fat levels in the dough, hinder gluten development [21]. The texture is a sensory property of food and determine consumer acceptability [46].