Effects of Aloe Vera and Guava Leaf Extract on Threadfin Bream Surimi Gel: Physicochemical, Textural and Rheological Properties

Polyphenol-mediated protein interactions offer a promising approach for improving surimi gel networks. Nevertheless, the comparative and combined effects of polyphenol-rich plant extract and polysaccharide-based additives on gel properties remain insufficiently explored. Therefore, individual and combined effects of dechlorophyllized guava leaf extract (DGLE), a source of polyphenols and aloe vera powder (AVP), an acemannan-rich polysaccharide, on the physicochemical, textural and rheological properties of threadfin bream (Nemipterus spp.) surimi gel were investigated. DGLE obtained by ultrasonication followed by dechlorophyllization exhibited high total phenolic content (439.35 ± 4.72 mg GAE/g dry extract) and total flavonoid content (666.66 ± 60.52 mg QE/g dry extract). LCMS/MS-QTOF profiling tentatively identified 12 phenolic compounds, including ellagic acid, catechins, quercetin glycosides, EGCG, etc. Surimi gel incorporated with 0.2% AVP and 0.05% DGLE individually achieved the highest breaking force and deformation with minimum expressible moisture content, though whiteness decreased with increasing concentrations. SDS-PAGE and FTIR analyses confirmed polyphenol-protein interaction and acemannan-gel network association. Gel with 0.2% AVP alone showed the highest hardness, gumminess, chewiness and elevated G′, while 0.05% DGLE alone yielded the highest springiness and cohesiveness, consistent with dense cross-linking observed in SEM (p < 0.05). AVP combined with DGLE exhibited a reduced gel-strengthening effect, especially at increasing DGLE concentrations. Thus, DGLE alone at 0.05% improved surimi gel properties. This finding could provide insight into the use of DGLE as a natural additive to improve surimi gel.