Characterization of the secondary structure, renaturation and physical ageing of gelatine adhesives

Animal glues have been used for centuries, but their popularity decreased in the 20th century with the rise of synthetic adhesives, leading to their current primary use in restoration. Despite this decline, gelatine, derived from denatured and partially hydrolysed collagen, has gained popularity in various applications. This study focuses on gelatinous glue samples derived from animal bone and hide tissues, examining their secondary structure and thermal properties to identify structure-property correlations. Infrared spectroscopy analysis has revealed differences in the secondary structures, with hide glues exhibiting more β-structures than bone glues, indicating a higher degree of aggregation. Thermogravimetric analysis and differential scanning calorimetry also have highlighted differences between hide and bone glues, showing that the latter are more hydrolysed. Furthermore, the calorimetric curves have showed different values of denaturation enthalpy thus indicating a different degree of gelatine renaturation. Additionally, the calorimetric analysis has demonstrated the physical ageing of gelatinous glue samples, a key factor in maintaining adhesive properties for long-term use under specific storage conditions. In a context prioritizing the use of waste biomass over fossil fuels, understanding the properties of gelatine in glues is crucial for enhancing their performance and promoting their adoption as sustainable alternatives to non-renewable adhesives.