Thermal and shear response of a novel shear-thickening polysaccharide from Parablechnum novae-zelandiae (Kiokio)

This study reports a naturally shear-thickening gum extracted from Parablechnum novae-zelandiae (kiokio) – a highly abundant fern native to New Zealand, and systematically investigates its temperature and shear sensitivities. Naturally shear-thickening hydrocolloids remain rare and their processing-induced structure–function relationships are poorly understood. The shear-thickening behaviour of kiokio gum (KG) has potential for satiety management and texture-modified food systems. Crude kiokio gum was subjected to temperature (45–121 °C, 30 min) and shear treatments (high-shear mixing: 1k–8k rpm for 1–20 min and microfluidization: 500–2000 bar) and rheological and molecular properties assessed. Temperature treatments caused significant temperature-dependent reductions in shear viscosity, extent of shear-thickening, viscoelastic properties, extensional viscosity, weight-average molecular weight (M w ) and radius of gyration (R g ). Post-shear treatments resulted in similar reductions under prolonged or extreme shear, indicative of shear-induced depolymerisation. However, under milder and shorter shear treatments (1k–8k rpm, 1 min), M w was unchanged and the decrease in R g indicated conformational rearrangement rather than chain scission. These findings establish the processing window within which the functional properties of KG are preserved, providing a basis for its incorporation into food systems and informing processing strategies for naturally shear-thickening polysaccharides.