Development and Evaluation of a Freeze-Dried Laver Soup: Effects of Rehydration Methods on Physicochemical and Sensory Quality

Laver (Pyropia spp.) is an adaptable and environmentally sustainable marine food that is rich in nutrients and increasingly incorporated into sustainable food systems. This study evaluated the quality characteristics of an instant freeze-dried laver soup produced by vacuum freeze-drying and rehydrated using three common household methods: hot water soaking (HW), boiling (BW), and microwave heating (MW). Physicochemical properties (rehydration ratio, pH, salinity, soluble solids, color, texture), free amino acid profiles, and consumer sensory attributes were analyzed. The BW method yielded the highest rehydration ratio and the most favorable sensory acceptance, comparable to the freshly prepared control. All rehydrated samples showed elevated levels of sweet- and umami-related amino acids (e.g., alanine, threonine, taurine), although the total free amino acid content decreased overall. Rehydration also reduced hardness and chewiness, while increasing lightness (L) and decreasing redness (a). Sensory evaluation confirmed that BW best preserved key flavor and mouthfeel attributes, most closely resembling the control. These findings support the development of shelf-stable, environmentally sustainable, seaweed-based instant foods, highlighting the importance of optimized rehydration strategies for consumer acceptance.