## 3 Results
### Chemical Characterization  
GC-TOF-MS Analysis  
After harvesting and, especially, during the storage period, the seaweeds release VOCs which, concisely, can arise from three main sources: compounds derived from their metabolism, those from microbial activity, and substances present in seawater that adhere to their surface (including contaminants) [56; 57; 58]. The analysis described here allowed for the detection of 126 VOCs for _P. umbilicalis_ and 148 for _U. lactuca_. These compounds could be divided into groups characterized by the presence of the following functional groups: alcohols, aldehydes, carboxylic acids, esters (of fatty acids and lactones), hydrocarbons, and ketones (including acyloins). A \"diverse\" group was used to aggregate minor VOC categories. As shown in Figure 6, most of the VOCs in both seaweeds belonged to the aldehyde group, of which 36 VOCs were identified for PU and 37 VOCs for UL. The next most represented category was that of the alcohols, of which 23 VOCs were identified for PU, and 27 VOCs in UL. The third most abundant group was hydrocarbons for PU (20 VOCs) and ketones for UL (22 VOCs). In the \"diverse\" group, the categories of compounds included were different for each of the seaweeds, as well as the number of compounds for each category. The following VOCs were identified for PU: three nitrogen-containing, one sulfur-containing, one epoxide, six furans, one indian, one ketose, two phenols, one pyridine, and four terpenoids. For UL, the following VOCs were identified: one nitrogen-containing, four sulfur-containing, four halogenated VOCs (two bromine-containing, one chlorine-containing, one iodine-containing), one benzothiazole, one epoxide, eight furans, three indans, one naphthol, four phenols, one terpene, and three terpenoids. Regarding the characterization of the functional groups throughout the storage days, there was not a great variation in terms of the number of compounds identified for most samples, with a few exceptions (see Supplementary Material, Figure S1). For PU, there was an increase in aldehydes and compounds from the \"diverse\" group in VAC. The number of esters seemed to decrease in VAC, as well as the number of hydrocarbons, which was relatively smaller in relation to CTRL and MAP. For UL, in all samples, the number of alcohols (except for MAP on day 15 and VAC on day 6) and ketones (except for MAP on day 12 and VAC on day 6) appeared to increase in comparison with day 0, with greater intensity for those from CTRL. The esters seemed to decrease with storage time for all the treatments. It is important to notice that some acetic acid was found in VAC throughout storage, whereas it was not detected in CTRL or MAP--except on day 3, where a trace amount of this compound was detected in the latter. Tukey HSD results (see Supplementary Material, Table S2) for _P. umbilicalis_ revealed that there were no significant differences among both the MAP and VAC treatments and CTRL--only on day 6 did the medians differ in relation to day 0, despite two-way aligned rank transformation ANOVA showing only marginal significance for the days (Pr(>F) = 0.096001). The results for _U. lactuca_ showed no difference between the MAP and VAC treatments, although both differed significantly from CTRL. While CTRL did not differ significantly between the days of storage, the MAP and VAC treatments showed significant differences in relation to day 0; nevertheless, no significant changes were observed from day 3 onward. For PU, the first principal component (PC-1) accounted for 50% of the variance of the samples, while the second principal component (PC-2) contributed 35%, together explaining 85% of the total variance. For UL, the PC-1 accounted for 43% of the variance of the samples, the PC-2 contributed 27%, and the third principal component (PC-3) explained 12%, together describing 82% of the total variance. Examining Figure 7a, the PCA was able to group the PU samples by type of treatment, which were in different zones of the score plot--except for the VAC treatment on day 15.