Compositional and structural aspects of hydro- and oleogels: Similarities and specificities from the perspective of digestibility

Abstract Background. This review sheds light on some important aspects to consider when formulating either hydrogels or oleogels for food applications. Despite food gels ubiquity, their digestibility behavior is still little understood limiting our capacity to fully harness their functionalities. Scope and approach. Insights are provided on how each ingredient and interactions thereof (including bioactive compounds) are involved in the gel formation and its behavior within the gastrointestinal tract (GIT). We also signaled the role of gel structure towards GIT conditions, opening the opportunity to design a soft matter aiming to disintegrate or promote the controlled release of bioactive compounds. A picture about the similarities and specificities of hydrogels and oleogels concerning the opposite nature of their continuous phase, as well as about the role played by different structuring agents is discussed. Key findings and conclusions. Hydrogels have a biopolymer-oriented digestion behavior (e.g. non-digestibility/fermentation of non-starch polysaccharides, starch hydrolysis by α-amylases or protein by proteases), which undergoes conformational changes (e.g. non-equilibrium swollen state) affected by the presence of charged groups. Whereas, the digestion of oleogels depends both on mechanical strength of the bulk structure (mainly affecting lipolysis) and hydrolysis of oleogelators (e.g. polymers, crystalline species, proteins) affecting their transient clusters. The outstanding properties of gels as a texture modifier and encapsulating system are primordial reasons for unveiling the function of ingredients and their interactions underlying structure digestion behavior. Thus, allowing the development of edible gels with the possibility of pre-setting their techno- and bio-functionalities.