Abstract <p>The edible seaweed <i>Pyropia columbina</i> thrives along coastlines worldwide and is rich in water-soluble sulfated galactans with valuable technofunctional properties for innovative applications. However, the impact of processing on <i>P. columbina</i> remains largely unexplored, limiting its application as an ingredient in food products. The objective of this study was to investigate <i>P. columbina</i> dispersions obtained by food processing i.e., thermal treatment (45-90 <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(^{\circ }\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>C), high shear treatment (HPH 15-50 MPa, 1–3 passes), and their combinations. The chemical composition, particle size, microstructure, and rheological properties were analyzed. Our results revealed that the seaweed presented a thick extracellular matrix (ECM), which was disrupted by high shear treatment, reducing particle size and cell–cell adhesion. The viscosity of the liquid phase increased with processing temperature (45–90<InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(^{\circ }\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>C) due to a higher release of cellular components. High shear treatment had no impact on the viscosity of the liquid phase, whereas the combination of thermal and high shear treatments enhanced its viscosity. The liquid phase contained approximately 16–22% protein and was enriched in galactose (80–90% of the identified total monosaccharides). In conclusion, the viscosity of the liquid phase was a key factor for the overall flow behavior of the seaweed dispersions, which belonged to the dilute to semi-dilute regime and showed a range of rheological behaviors from liquid (tan<InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\varvec{\delta }\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="bold-italic">δ</mi> </mrow> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\varvec{&gt;}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo mathvariant="bold">&gt;</mo> </mrow> </math></EquationSource> </InlineEquation> 1) to soft gel (G<InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\varvec{'}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mrow /> <mrow /> <mo mathvariant="bold">′</mo> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation> &gt; G<InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\varvec{''}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo mathvariant="bold">′</mo> <mo mathvariant="bold">′</mo> </mrow> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation>). These findings contribute to the optimization of red seaweed use as a source of sustainable ingredients in food products.</p> Graphical abstract <p></p>