## 4 Discussion
### Antimicrobial Activity
These interactions highlight the potential of using _Gelidium_ sp. alga flour and gelatin films in food packaging to increase the delivery and effectiveness of bioactive components, contributing to better food preservation and safety. In the present study, further investigations of the antimicrobial compounds were not conducted. However, owing to the use of an aqueous extract of red alga flour, the observed antimicrobial effect is likely due to the presence of hydrophilic constituents. Hydrophilic compounds with preservative properties, such as sulfate polysaccharides, proteins, peptides, glycosides, low-molecular-weight organic acids, and salts, have been reported to have preservative effects [58; 59]. Notably, previous research has documented the antimicrobial properties of hydrophilic constituents isolated from red algae and aqueous extracts obtained from red macroalgae in both in vitro and real seafood studies. In previous studies, glycolipidids isolated from the red algae _Laurencia papillosa_ and _Galaxura cylindrica_ have demonstrated antimicrobial activities in vitro, which are attributed to their compositions with high contents of monosaccharides such as mannuronic acid, galactose, and rhamn [60]. [PERSON] et al. [27] reported that sulfated polysaccharides from _Gracilaria corticata_ exhibited antibacterial effects against various bacterial pathogens, including _Salmonella typhi, Salmonella paratyphi, Staphylococcus aureus, Vibrio cholerae,_ and _Klebsiella oxytoca_. Additionally, sulfated polysaccharides from _Gelidium pacificum_ showed potential beneficial effects on mice by means of the recovery of their gut microbiota and improving mucosal barrier function [36]. Both cold and hot aqueous extracts obtained from _Petercoladia capillacea_ displayed significant antimicrobial effects in vitro [61]. The cold-water extract was notably rich in glucuronic acid, arabinose, and glucose, whereas the hot extract was rich in glucuronic acid and fructose. [PERSON] et al. [34] reported that both aqueous and ethanolic extracts of the red alga _Gelidium pusillum_ inhibited the marine pathogen _Aeronomas caviae_ in vivo. Other studies have also shown the in vitro antibacterial effects of ethanol and aqueous extracts from various red algae (_Gracilaria chilensis, Gelidium chilense, Iridaea larga, Gigartina chamissoi, Gigartina skottsbergii,_ and _Gigartina radula_) against _Salmonella enteritidis, Bacillus cereus,_ and _Escherichia coli_[37]. Previous studies have reported that the presence of macroalgae in different types of packaging has inhibitory effects on microbial activity in seafood systems. For example, antimicrobial activity was observed in fish paste inoculated with _E. coli_ O157:H7, _Listeria monocytogenes_, and _Salmonella typhimurium_ via an active packaging strategy with a _Gelidium corneum_-whey protein isolate film [35]. The inclusion of an aqueous extract of the red macroalga _G. corneum_ in an edible film enhanced its physical properties (tensile strength, elongation at break, and water vapor permeability) and provided antimicrobial activity [62]. A reduction in microbial activity (lower aerobe counts, psychrotrophs, and TMA-N formation) was noted in refrigerated megrim (_Lepidoptera whifftagonis_) by incorporating lyophilized _Fucus spiralis_ into a polylactic acid film [63]. The use of an icing medium containing ethanolic and aqueous extracts of the red alga _Gracilaria gracilis_ also inhibited TMAformation during the chilled storage of hakes (_Merlucius merlucius_) [64]. Additionally, soaking chilled black tiger shrimp (_Peneus mondon_) in ethanolic-aqueous extracts of red seaweed (_Hypnea musciformis_ and _Acanthophora muscoides_) resulted in lower biogenic amine formation and extended shelf life [65]. Recently, a reduction in microbial activity (aerobic mesophilic and psychotrophic counts) was observed in refrigerated mackerel (_S. scombrus_) by incorporating _F. spiralis_ powder into a gelatin-based active film [41].