## 3 Results
### Physicochemical Characterization
#### 3.2.1 Color  
As shown in Figure 2(a),b, the coordinate \(L^{*}\) became slightly lighter for both seaweeds throughout the storage days. Although no significant effect of the treatments was observed in _P. umbilicalis_ (PU), the lightening seemed to be more pronounced on _U. lactuca_ (UL) in the CTRL and VAC samples. Figure 2: The composition of headspace gases for O\({}_{2}\) and CO\({}_{2}\) throughout storage days for _P. umbilicalis_ (**a**,**c**) (left column) and _U. lactuca_ (**b**,**d**) (right column) controls (**a**,**b**) (upper line) and MAP-treated seaweeds (**c**,**d**) (lower line). Notes: The results are expressed as % of the headspace composition. Means \(\pm\) SD from triplicate determinations on each experiment. Means followed by a different lowercase letter are significantly different (\(p<0.05\)) throughout storage days. Means followed by a different uppercase letter are significantly different (\(p<0.05\)) between seaweed species (same treatment and gas). Regarding the \(a^{\star}\) coordinate (Figure 3c), a difference was observed for the MAP and VAC treatments for PU relative to CTRL on days 12 and 15. From day 9 onwards, the values seemed to increase for red, especially for the VAC treatment, which doubled (from 6.72 to 13.25). For UL (Figure 3d), whose coordinates were on the negative (green) side of the \(a^{\star}\) axis, the MAP and VAC treatments were statistically different compared to CTRL from day 6 onwards. The values for the CTRL, MAP and VAC treatments grew in different  
Figure 3: Color changes throughout storage days for _P. umbilicalis_ and _U. lactuca_ preserved by different treatments. The results are expressed as the CIELAB coordinates for \(L^{\star}\), \(a^{\star}\), \(b^{\star}\), and the calculated color deviation (\(\Delta E\)). Notes: Medians and interquartile range (IQR) from duodecuple determinations on each experiment. Medians followed by a different lowercase letter are significantly different (\(p<0.05\)) throughout storage days. Medians followed by a different uppercase letter are significantly different (\(p<0.05\)) among treatments. patterns and, on day 15, an increase was observed from \(-14.73\) on day 0 to \(-10.58\), \(-9.17\), and \(-8.43\), respectively. For the \(b^{*}\) coordinate of PU (Figure 3e), a difference relative to CTRL could be observed for the MAP and VAC treatments from days 12 and 9 onwards, respectively. While the values did not change significantly for CTRL throughout the storage days, the values for the MAP treatment ranged from 27.74 on day 0 to 19.31 on day 15. For the VAC treatment, a median of 1.68 was observed for the last day (6% of the initial value), which demonstrates an almost inversion from positive to negative values--i.e., a change from the yellow component to the blue one. For UL (Figure 3f), a large variation in the values in several directions was noticed, making it difficult to detect a trend. Nevertheless, on the last day, a decrease in the values for the CTRL and VAC treatments could be observed, while the MAP treatment seemed to maintain the reference value. In other words, a positive change of the \(a^{*}\) value on the red axis together with a negative change of the \(b^{*}\) value on the yellow axis in the CIELAB color space indicated a shift in color towards a maroon (dark brownish red) color for PU. For the VAC treatment on day 15, it could also be stated that, in the case of overturn from yellow to blue, in combination with a redder tone with respect to the original color, a resulting violet color could be perceived. For UL, a positive change in the \(a^{*}\) value on the green axis together with a negative change in the \(b^{*}\) value on the yellow axis indicated a change in color towards a more olive-green tone (see Supplementary Material, Table S1). The \(\Delta E\) values for PU (Figure 3g) showed a larger color deviation for VAC, especially on days 12 and 15. CTRL showed the best results for PU on the last day of the experiment, but the color did not differ statistically from the MAP treatment.