Freeze-thaw and freeze-heat modification of starch - a comprehensive review on structural and physicochemical...

Freeze-thaw modification has emerged as an effective non-chemical approach for enhancing the functional properties of starch in a range of applications. These include frozen food systems, bioplastics, and pharmaceutical formulations. Through repeated cycles of freezing and thawing of raw starch, alternatively by combining gelatinization/heating with subsequent freeze-thawing (FT), this technique can induce molecular reorganization, increase surface roughness, and promote formation of pores in the starch granules. These structural alterations are capable of contributing to a vast variation in important functionalities such as improved water retention, oil adsorption, reduced gelatinization enthalpy and relative crystallinity (RC), decreased syneresis, improved FT stability, which is the capacity of starch systems to withstand water separation (syneresis) and structural breakdown when subjected to repeated freezing and thawing, and enhanced RS content. Freeze-thaw (FT) and freeze-gelatinization treatments are increasingly recognized as important physical modification strategies, particularly in light of growing demand for natural, clean-label ingredients. However, practical use remains challenged by high energy requirements, prolonged processing times, and variability in performance, related to differences in botanical origin and molecular structure among different starch sources. Recent advancements in analytical techniques adapted for structural characterization of starch, along with the developments of physical, chemical, and enzymatic modification methods, can mitigate such limitations. Such combined approaches is expected to enable the production of starch-based materials with improved mechanical properties, thermal stability, and batch-to-batch consistency. With this review, we outline the underlying mechanisms of FT and freeze-heat (FH) modification. Selected current industrial applications are evaluated and their potential as sustainable tools for tailoring starch functionality in both consumer and technical products are discussed.