Evaluating the Sensory Profile and Quality Traits of Sparus aurata Fed Sustainable Diets

Sustainable Mediterranean aquaculture requires reducing fishmeal (FM) and fish oil (FO) use without compromising product quality. This study evaluated the effects of three isoenergetic and isoproteic diets—control fishmeal (FM), processed animal protein diet (PAP), and an alternative diet containing insect meal and microbial biomass (ALT)—on the physical, chemical and sensory properties of gilthead sea bream (Sparus aurata) at two catch weights (300 and 800 g). Texture and cooking weight loss were largely unaffected by diet, whereas PAP and ALT increased post-cooking yellowness and chroma. PAP showed the highest content of sweet and total free amino acids (FAAs), while umami FAAs remained unchanged. Gas chromatography identified 55 volatile organic compounds (VOCs), dominated by terpenes (49–54%, significantly higher in PAP and ALT), although lipid oxidation markers were similar. Sensory analysis revealed higher post-cooking chewiness and hardness in ALT, and enhanced umami for both alternative feeds. Consumer testing (n = 81) yielded high acceptance scores (>5/11-point scale) across treatments, with PAP scoring higher for oily flavor, textural oiliness, and aftertaste—an effect potentially linked to fatty acid composition rather than total fat content. Overall, replacing FM with PAP or ALT offers a sustainable feed strategy that preserves filet quality and consumer appeal.