Harpiosquillid mantis shrimp (Harpiosquilla raphidea) (HMS) without and with beheading pretreated with pulsed electric field (PEF) (15 kV/cm, 800 pulses, 5 min) were soaked in chitooligosaccharide (COS) solution at varying concentrations (0, 1 and 2%, w/v) for 20 min and stored for 3 days in iced water. Changes in the trypsin activity, color, texture, protein pattern, TCA soluble peptide content, histological images, protein secondary structure and microbial load were monitored during the storage. The beheaded HMS pretreated with PEF and soaked in 2% COS solution showed the maximum efficacy in inhibiting trypsin activity and proteolysis, thus retaining muscle proteins, especially myosin heavy chain, actin and troponin T as well as shear force up to day 3. Pronounced muscle destruction in the whole HMS was displayed by a decreased mean grey index and fiber gapping. Such changes were lowered by the beheading and PEF/2% COS treatment (2% COS-BH). Nevertheless, no marked change in the secondary structure including α-helix, β-sheets, β-turns and random coil were observed among any of the samples. The microbiological analysis revealed that the total viable count (TVC) was below 6 log CFU/g till day 2 in all samples. Nonetheless, the 2% COS-BH sample had the lowest psychrophilic bacterial count and Enterobacteriaceae count at day 3, compared to the others. Thus, the combination of the prior PEF and 2% COS treatment of beheaded HMS could effectively inhibit proteases, retard the microbial growth and maintain the quality of HMS stored in iced water.

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.

Fish roe is consumed in different forms, e.g., caviar. The large and firm spherical roe from giant sea catfish (GSC, Arius thalassinus), which have a high price, are popular in some countries, like Thailand. However, the information on their nutrition and properties is scarce. Roe of different sizes from GSC, including medium (GSC-M), large (GSC-L), and extra-large (GSC-XL) sizes, were rich in protein (29.52–32.70%), fat (4.07–5.65%), and essential amino acids, particularly leucine and lysine. Vitelline was the major protein in GSC roe. Polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexaenoic acid, were abundant, although GSC-M showed lower PUFA content (21.91%) than GSC-L and GSC-XL (25.56–25.94%). No significant differences in texture property were found between sizes, despite the microstructural and histological differences. Larger voids and strands were found with augmenting size, while GSC-L showed greater membrane thickness (133.55 µm). FTIR spectra confirmed the presence of peptide and ester bonds associated with proteins and triacylglycerols, respectively. GSC-L had the highest cholesterol content (651.2 mg/100 g), whereas GSC-M showed the highest α-tocopherol level (1.64 mg/kg). Phosphorus was the dominant mineral (3473–3894 mg/kg), followed by calcium and other minerals. Hence, the roe from GSC, regardless of size, possess high nutritive value and could be used as a wholesome marine food or functional ingredient.

Bleeding enhances fish quality by removing blood, which acts as a pro-oxidant and provides nutrients for microbes. However, the effects of bleeding techniques on freshness, quality, and fishy odor of Asian seabass remain unclear. Therefore, the effects of gill cut (GC) and water perfusion (WP) bleeding on slices during 12-day refrigerated storage were investigated. Freshness was retained in bled samples, particularly GC, as indicated by lower K-values during storage. Protein oxidation was higher in WP than GC samples, as shown by higher carbonyl content in the former during the storage. This coincided with lower sulfhydryl content, except during day 3–6 in which there was no difference between both samples. Similar fishy odor intensity between GC and WP was observed during storage, except GC showed lower intensity on day 6, whereas unbled samples (UB) exhibited higher intensity through the storage. Pearson correlation and principal component analysis (PCA) confirmed relationship among bleeding methods, microbial growth, and quality changes. Boxplot analysis supported the results by showing variation in quality indicators among treatments. GC therefore preserved freshness, retarded microbiological and biochemical changes, and retained textural properties. GC tended to reduce fishy odor formation more effectively than WP, particularly at intermediate storage stage.