## 4 Discussion
### Physicochemical Characterization
#### 4.2.2 Texture  
The studies encountered in the literature about the texture analysis of fresh seaweeds subjected to different storage conditions or treatments are scarce, and the methodologies used vary greatly between trials. It was not possible to find analyses for fresh _P. umbilicalis_ (or any other layer seaweed) over a storage period. Therefore, the results for other red seaweeds or those with laminar thalli were used as references.  
The Nayyar & Skonberg [92] texture profile analysis (TPA) for _Palmaria palmata_ (Rhodophyta) showed that hardness values were notably impacted by both time (2 weeks) and temperature (2 \({}^{\circ}\)C and 7 \({}^{\circ}\)C), with values decreasing gradually over time and more intensively for higher storage temperatures. For _Gracilaria saliconia_, the majority of the thalli had lost their firmness by the end of the storage period of 6 days at 16 \({}^{\circ}\)C or 21 \({}^{\circ}\)C in the light or dark. However, this decline could not be correlated with either the storage temperature or light conditions due to the considerable variability in the texture values [35]. These results are not in accordance with our findings for PU-CTRL, although it must be considered the _P. umbilicalis_ has different morphology and textural characteristics from _P. palmata_ and _G. saliconia_.  
Research on the use of HPP for _U. lactuca_ did not find significant texture differences for the control on the 30 th day of storage at 4 \({}^{\circ}\)C, just as with UL-CTRL in our research. This  
Figure 9: (**a**) Color differences for _U. lactuca_ between treatments on _day 9: control_ (left), _MAP_ (center), and _vacuum_ (right); (**b**) Color of the seaweeds _U. lactuca_ (left) and _P. umbilicalis_ (right) on _day 0_.  
was not true for the same seaweed treated with 400 MPa, which seemed to lose hardness only after 30 days of storage. Cell disruption and lyase activity (bacterial or endogenous) seemed to be the reason for such deterioration [32]. TPA on the sensory characteristics of _U. rigida_ indicated that the hardness values were influenced by storage duration (12 days) and temperature (4 \({}^{\circ}\)C and 16 \({}^{\circ}\)C), with a gradual decrease observed over time at both temperatures. This weakening of the cell structure may have occurred due to chemical and enzymatic reactions, and even microbial activity, making the tissue more fragile and susceptible to breakage [79].  
Based on what was previously discussed, it appears that seaweeds can present different behaviors depending on the evaluated species or experimental conditions [32; 79; 92]. Furthermore, the same species may show high variability in their textural properties related to the collection site, uneven decay, or tissues analyzed [35; 42; 43]. These reasons account for the varying behavioral patterns observed in the addressed works.  
Our results showed that hardness values for the CTRL and MAP treatments were generally comparable, whereas the VAC treatment exhibited some degree of variability, with _P. umbilicalis_ prone to become less resistant on day 15. While many studies suggest that the decline in hardness of the seaweeds may be attributed to chemical or biological factors, there is no evidence in the current study to support the deterioration of seaweed by microorganisms, as PU-VAC exhibited the lowest microbial count on day 15. Most likely the variations in VAC treatment resulted from the compression of the seaweeds by the vacuum package that may have caused some random break in the cell matrix in a similar way to what happened for the HPP-treated seaweeds. The breakdown of cell structure and aging, alongside a loss of intracellular content, could have promoted autolysis reactions in samples [32]. The key finding was that MAP may be a more effective preservation method in maintaining the textural properties of fresh seaweeds compared to VAC.