Physicochemical Quality and Flavor Characteristics of Sevenband Grouper (Hyporthodus septemfasciatus) Fillets: Effects of Boiling, Steaming, Oven Cooking, and Microwave Cooking

Sevenband grouper (Hyporthodus septemfasciatus) is a premium aquaculture species with a high-protein, low-fat profile, yet cooking-related quality data remain limited. This study evaluated the effects of boiling, steaming, oven cooking, and microwave cooking on the physicochemical, flavor-related, and microstructural properties of grouper fillets. Weight loss differed significantly among methods (p < 0.001); oven cooking produced the greatest loss (32.42 ± 3.17%) and boiling the least (16.66 ± 3.89%). Shear index decreased after cooking; boiling produced the softest texture (75.57 ± 28.49 g·s), while steaming remained the firmest (192.46 ± 9.12 g·s; p < 0.001). pH and lightness (L*) increased after heating in most methods, but microwave-cooked samples showed pH similar to raw fish, whereas oven cooking produced the greatest yellowness (b* = 21.54 ± 0.44). E-nose analysis (PC1 = 53.79%, PC2 = 20.51%) separated moist-heat samples from oven-cooked samples. E-tongue analysis showed increased sourness after oven and microwave cooking and decreased saltiness after microwave cooking, while umami showed no clear change. Microstructural analysis showed the widest inter-fiber spacing in oven-cooked samples, matching greater moisture loss. These findings provide physicochemical, flavor-related, and microstructural data for sevenband grouper and support future processing and product development.