Water-polysaccharide interactions and their properties in freezing conditions

Freezing processes involving polysaccharides are widespread, spanning from organisms resisting cold environments, to emerging applications for cryopreservation in biomedical and food technologies. Yet, many fundamental questions on these processes remain unanswered. The challenge arises both from the complexity of polysaccharides and their structure and from water, a simple molecule with unique properties; such complexity can only be understood using a strongly interdisciplinary approach spanning through physics, chemistry, materials science and engineering. This review explores the current understanding of the complex phenomena underpinning the behavior of water when interacting with polysaccharides, with a special interest at freezing conditions, when ice forms. Herein, we draw a comprehensive picture on the most relevant findings, connecting scientific knowledge from diverse fields, from chemistry to biotechnology, materials science and engineering, all linked by the interest in water-polysaccharide interactions, especially at interfaces. After introducing the key concepts related to the structure of water at the interface with polysaccharides, such as bound water, non-freezing water and quasi-liquid layer, the review compares the main techniques used to study the polysaccharide-water interaction in freezing conditions, discussing the relevant findings for a variety of polysaccharides.