Enhancing Dark Chocolate with Fermented Laver (Porphyra umbilicalis): Effects on Sensory Characteristics and Consumer Acceptance

Seaweed is increasingly recognized as a sustainable food source with the potential to contribute to Western diets; however, consumer acceptance remains low. This is partly due to undesirable sensory attributes, including fishy and marine flavours present when seaweed is incorporated into foods. Fermentation has been proposed to minimize these off-flavours. This study evaluated the impact of fermentation on the sensory properties of Porphyra umbilicalis (laver). Dark chocolate (54.5% cocoa) was enriched with laver fermented using three cultures: Streptococcus thermophilus (ST), Pediococcus pentosaceus (PP), and Aspergillus oryzae (AO). Five formulations were assessed for consumer acceptability (n = 83) using nine-point hedonic scales and check-all-that-apply (CATA) questionnaires for sensory and emotional responses. All seaweed-containing samples received significantly lower liking scores than the control (overall liking: control = 7.8 ± 0.9; seaweed samples ranging from 5.7 ± 1.8 to 6.6 ± 1.5). Among seaweed-containing samples, AO-fermented laver achieved the highest flavour liking (6.5 ± 1.7) and overall liking (6.6 ± 1.5) scores, both significantly higher than the unfermented sample (flavour: 5.7 ± 1.8; overall: 5.7 ± 1.8; p < 0.05). Correspondence analysis of CATA data explained 88.01% of total variation, with the control associated with positive sensory attributes (sweet, creamy, smooth) while seaweed samples were characterized by off-flavours, fishy, and earthy descriptors. Emotional profiling using the EsSense25 profile indicated that the unfermented sample was exclusively associated with negative emotions (bored, worried, disgusted), while AO was associated with seven positive emotional terms. These findings suggest that fermentation, particularly with AO, may improve the sensory acceptability of seaweed in Western food products when incorporated into familiar matrices. Further research should examine different seaweed species and fermentation strategies to enhance consumer acceptance.