## 3 Results
### Physical Properties of Corn-Based Crisps Supplemented with Fruits
However, slightly lower WAI was noted if 15 and 20% supplement was used, but differences were smaller than in previous samples with apples and white mulberries. The water solubility of the supplemented crisps was almost twice lower than control corn-based crisps, but differences between samples with various amount of additive were small. [PERSON] et al. [26] tested extrudates processed by single screw extrusion from quinoa enriched with goji berries at 1, 3 and 5% and found decreased of WAI from 8.05 to 6.34 g/g of product when the two variables (moisture content and additive amount) increased simultaneously. The increase of the goji berries' amount causes the increase of lipids in composition that can interacts with starch from quinoa and limits the gelatinization degree. Moreover, increasing the amount of goji berries in the recipe of snacks had the effect of lowering the water solubility of the extrudates but the effect of the moisture content was more pronounced. Table 6 presents the results of selected properties of corn-based crisps supplemented with elderberry fruit powder. In our work, the samples with various amounts of elderberry powder expanded very well and their bulk density was the lowest from all the tested snacks. This additive was very useful for achieving well expanded snacks with low bulk density. Accordingly, 5% of additive did not differ in values of EI from control samples, but in samples with even 20% of elderberry fruit, the expansion index was over 2, this was twice as more than if apple, mulberry or goji berry were used. A very good bulk density with maximum value of 109.40 kg/m\({}^{3}\) was evident if 20% of elderberry fruit was applied. This outcome demonstrates that this additive proves excellent for obtaining highly expanded and light in weight supplemented snacks. Being connected with low density, the water absorption of the resulting crisps was very high in the whole range of additive levels and screw speeds applied. Moreover, intensive treatment brought about similar effects on treated components regardless of whether elderberry fruits varied in supplement quantity. Finally, the water solubility of the supplemented snacks was lower than control, but it also was independent of variation supplementation level or screw speed applied. Corn-based crisps with blackberry powder addition were also well expanded, with low bulk density up to 115.43 kg/m\({}^{3}\) if 20% of fruit additive was used (Table 7). The slightly less expansion in samples with 20% of additive did not significantly affect overall impression of the aptitude of blackberry powder supplementation in corn-based crisps recipe. Application of 5, 10 and 15% of blackberry fruit showed similar effect on EI, BD, WAI and WSI. Here, only small differences were noted regarding physical properties even if 20% of fruit powder was applied. The exception was WSI, which was insignificantly affected both by fruit addition and screw speed. This may be the effect of high content of fruit sugars (fructose and glucose), which varied from 39.90 to 45.12 g/100 g d.m. for mature and fully mature fruits, respectively, as reported by [PERSON] et al. [38]. In related work, [PERSON] et al. [16] tested the influence of 2% and 4% of pumpkin flour addition on quality of extruded corn snacks. They found that the expansion ratio and water solubility index decreased, while the bulk density and water absorption index increased with increasing amount of additive. Overall Analysis of the Effect of Variables on Physical Properties of Corn-Based Crisps with Fruit Powders  
In analyzing the overall effect of fruits addition on the physical properties of corn crisps, the outcome of the experimental results were significantly different regarding expansion index (EI) between the additions of apple and elderberry, and white mulberry and elderberry (\(p\)-value 0.002; 0.0052 respectively). In the remaining cases, no statistically significant differences were found.