*3.6. Effects of Storage on Microstructural Characteristics*

Scanning electron microscope (SEM) was used to collect data on the structural integrity, size, shape, and arrangement of particles of both raw and cooked wheat noodles fortified with isomaltodextrin, which closely correlated with the cooking quality, texture profile, and sensory characteristics [34]. Figures 5–7 show the SEM micrographs of wheat noodles fortified with isomaltodextrin during different storage periods at 25, 4, and −20 ◦C, respectively. Micrographs of the raw isomaltodextrin noodle samples (before cooking) at 25 ◦C showed the well-formed fiber–starch matrix, with clearly seen isomaltodextrin particles attached to the starch granules. At 4 ◦C storage, the isomaltodextrin particles were partially adhered between each molecule and with the starch granules. The isomaltodextrin particles were frosted and held within starch granules to form a compact fiber–starch network because of the low temperature (storage temperature −20 ◦C). The starch granules within the noodle samples seemed to be a little swollen and with irregular size and shape, possibly demonstrating a gelatinization that occurred during the extrusion process [34]. Storage period did not affect the microstructure of the wheat noodles fortified with isomaltodextrin. SEM micrographs of raw noodle samples with isomaltodextrin showed a higher inclusion rate of soluble fiber in the binding relationship between starch and fiber (isomaltodextrin), which altered the general structural complexity of the noodle system.

Gelatinization of starch granules within the cooked noodle samples seems to be integrated into a developed fiber matrix to form a compacted noodles structure. The isomaltodextrin disturbs the structure with starch granules within the noodle matrix, causing loss of the regular structure and triggering the gelatinization process during cooking. The disruption to the isomaltodextrin noodles structures significantly affected the overall cooking quality and texture profiles of the isomaltodextrin noodles, which is described in Tables 1 and 3.

[6].

the long-term storage and directly affects the cooking characteristics of the noodle samples

**Figure 3.** Sensory evaluation of wheat noodles fortified with isomaltodextrin during different storage periods at 25, 4, and −20 °C storage. **Figure 4.** Sensory evaluation of wheat noodles fortified with isomaltodextrin during different storage periods at 25, 4, and −20 ◦C storage.

25 °C storage.

*Plants* **2021**, *10*, x FOR PEER REVIEW 13 of 17

**Figure 4.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at **Figure 5.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at 25 ◦C storage.

128

4 °C.

25 °C storage.

24

**Figure 5.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at **Figure 6.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at 4 ◦C.

−20 °C.

**4. Conclusions** 

**Figure 6.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at **Figure 7.** SEM of wheat noodles fortified with isomaltodextrin during different storage periods at −20 ◦C.
