## 3 Results and Discussion
### Microstructure  
The structure is one of the main factors determining the total quality of foods and also plays the key role in sensory evaluation. The SEM images of the cross-section and surface of dried kiwiberry foam mats are shown in Figure 4. As can be seen, the shelf temperature affected the structure. It has been stated that the foam mat structure dried at lower temperatures (10 \({}^{\circ}\)C and 25 \({}^{\circ}\)C) was more uniform compared to the sample dried at 40 \({}^{\circ}\)C. Overall, with increasing shelf temperature of freeze drying, the porosity and uniformity of the pore size distribution of the dried material decreased. The microstructure of the sample (10 \({}^{\circ}\)C) was characterized by a higher number of small pores compared to the others. A higher number of big and elongated cavities and, thus, a very low-density and uncompacted structure could be found for the samples dried at 25 \({}^{\circ}\)C and 40 \({}^{\circ}\)C. This phenomenon might be explained by the fact that at higher temperatures, the sublimation rate is generally higher, which may result in the collapse of the dried material and loss of the pore structure created by the freezing process. Moreover, with an increasing drying temperature and thus, enhanced heat and mass transfer, the combination of adjacent bubbles and therefore, collapse of the foam structure, may occur intensively, and also structural changes such as shrinkage [23] as well as decreasing of the material's complex viscosity, resulting in a decrease in porosity and structural collapse [18]. Figure 3: FTIR spectra of freeze-dried foam-mat kiwiberry pulp. It was previously reported that the temperature influences the porosity of samples. [PERSON] et al. [28] showed that by increasing the shelf temperature from room temperature to 40 \({}^{\circ}\)C during the freeze drying of grapefruit puree promoted a slight increase in the porosity and the mean area of pores. [PERSON] et al. [43] stated that foam-mat cantaloupe pulp dried at 55 and 70 \({}^{\circ}\)C had a higher number of pores compared to foam-mat cantaloupe pulp dried at 40 \({}^{\circ}\)C. [PERSON] et al. [63] observed the same relationships in the microstructure after drying of foam-mat shrimp at various drying temperatures (45, 60, 75 and 90 \({}^{\circ}\)C). Due to the shorter drying time at a higher temperature, the extent of collapse and coalescence of adjacent bubbles decreased and, as a result, caused more porosity and uniformity of the pore size distribution. Evaporated water during the drying process can cause various textural and structural changes. The total porosity of freeze-dried foam mats gained shown via XRCT scanning was from 57.7 to 65.6% (Figure 5). Kiwiberry foam-mat dried at 10 \({}^{\circ}\)C was characterized by the highest total porosity and visibly compacted structure. As expected, the decrease in porosity was noted with an increase of shelf temperature. The higher porosity may be identified along with less structural damage which occurred during drying at low temperatures [64]. Figure 4: SEM microstructure of cross-section (top row, magnification 50\(\times\)) and surface (down row, magnification 100\(\times\)) of foam-mat dried kiwiberry pulp. Figure 5: XRCT microstructure of foam-mat dried kiwiberry pulp. 1 Different letters within row for porosity indicate the statistical difference ([PERSON]’s HSD, \(p<\) 0.05). XRCT scanning allowed us also to identify the walls as well as pore size distribution. The foam mat dried at 10 \({}^{\circ}\)C was characterized by the lowest volume (97.0%) of pores smaller than 0.4 mm (Figure 6), while foam mats dried at 25 \({}^{\circ}\)C and 40 \({}^{\circ}\)C presented about 98.7 and 99.4% of the volume pores. Hence for the foam mat (10 \({}^{\circ}\)C), 3% of pores (larger than 0.4 and up to 1.4 mm) had a crucial impact on the higher porosity.