Cross-scale assessment of yam waxiness attribute from stress relaxation and fluid mechanics: A distinctive mouthfeel derived from starch matrix

Abstract

Research on evaluating waxiness and its underlying formation mechanisms remains limited. In this study, we established a comprehensive method for assessing yam waxiness by integrating sensory evaluation and instrumental analysis. By deconstructing waxiness evaluation into chewing and swallowing phases, stress relaxation and rheological tests were employed to characterize these stages. Key parameters, including equilibrium modulus (E₀), viscosity coefficient (η₁), consistency coefficient (K*), and loss modulus (G′′), were systematically utilized to accurately assess yam waxiness. Our investigation into the formation mechanisms of waxiness revealed that long starch chains (24 < X < 100 and 5000 < X 〈20,000) enhanced structural stability, leading to increased η₁ and G′′. These chains were integrated into both crystalline and amorphous regions of starch granules, thereby improving gel stability, elasticity, and viscosity, ultimately, this enhancing yam waxiness. Conversely, short-branched amylopectin reduced waxiness intensity by increasing E₀ of the starch gel.