From formulation proxies to control variables: A mechanistic framework for high-methoxyl pectin gelation and matrix...

High-methoxyl pectins (HMPs) have been the primary gelling agents in classic fruit systems with high sugar content and low pH for decades. Despite their widespread technological use, the field still lacks a coherent mechanistic framework comparable to the egg-box model established for low-methoxyl pectins. The literature remains dominated by formulation descriptors such as °Brix, pH, and nominal degree of esterification, which act only as indirect proxies of the physicochemical variables governing polymer network self-assembly. In this review, we propose a conceptual framework that interprets HMP gelation as a multiscale process controlled by solvent quality, water activity, cosolvent molality, molecular-weight distribution, and processing history. We introduce matrix organisation as a missing level of structural description linking rheological parameters with the predictability of stability and texture in food gels. Synthesis of evidence from model systems and real food matrices shows that identical elastic modulus (G') values may correspond to fundamentally different network architectures. Based on this analysis, we propose a minimum reporting standard for control variables to improve cross-study comparability and enable rational design of HMP systems, particularly in sugar-reduced reformulations.