<![CDATA[Graphical Abstract Highlights Research 1. Drying history altered E. cottonii functionality despite similar carrageenan yield. 2. Tray drying reduced moisture and increased whiteness, WAC, and gel hardness. 3. Gel hardness was shaped by drying method, pH, and CaCl₂ interactions. 4. Rheological responses to CaCl₂ varied non-monotonically with pH and drying history. 5. Sun-dried powder showed higher moisture uptake at the highest water activity. Abstract Post-harvest drying can modify seaweed powder functionality, yet whether extractable carrageenan yield reflects hydration, gelation, flow, and moisture sorption remains uncertain. This study compared tray-dried and sun-dried cottonii seaweed powders, identified by the cultivation source as Eucheuma cottonii, under controlled formulation conditions. The source-identified material lacked independent taxonomic verification, limiting species-level interpretation of these findings. Each drying treatment comprised three independent batches, although carrageenan yield was determined in two batches per treatment. Physicochemical properties and moisture sorption were measured, while gel hardness and steady-shear flow were examined in 2% (w/v) suspensions at pH 4.0 and 5.5 containing 0–4 mmol L⁻¹ CaCl₂. Tray-dried powder contained less moisture (7.87 ± 0.73 versus 9.70 ± 0.21%, wet basis) and had greater water absorption capacity (189.43 ± 3.50 versus 160.88 ± 1.30%). Carrageenan yields were 33.89 ± 0.35 and 34.03 ± 0.42%, respectively, without a detected significant difference (p > 0.05), which does not demonstrate equivalence. Reported gel hardness ranged from 46.06–63.68 gf after tray drying and 5.06–23.82 gf after sun drying. At pH 4.0 and 4 mmol L⁻¹ CaCl₂, shear stress at 100 s⁻¹ was approximately 19.3 versus 3.7 Pa; these rheological observations were descriptive because only one suspension was measured per condition. At water activity 0.93, equilibrium moisture contents were approximately 9.8 and 14.2% (dry basis). These contrasts suggest that carrageenan yield alone inadequately characterizes whole-powder functionality under the tested conditions. Independent verification of gel-hardness replication, replicated rheology, and molecular, ionic, and microstructural analyses are needed to substantiate and explain these differences. ]]>
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