Avallone, Pietro Renato (2022) Thermorheological behavior of edible hydrogels. [Tesi di dottorato]

Text Avallone_PietroRenato_34.pdf.crdownload Download (24MB)

Collection description

Hydrocolloids are a class of long chain polymers able to form gels or viscous solutions when dissolved in water. In recent years there is a growing interest in the study of hydrocolloids, due to their properties as stabilizers, thickeners and gelling agents. Different market survey, indeed, suggests that the global food hydrocolloid market will increase in value by minimum 50% within the next ten years. Hydrocolloids are widely used in food formulations, specially in confectionery products. Soft candies, such as jellies sweets, are a class of high-sugar confections based on hydrocolloids, in which the latter plays the role of gelling agent. The most used gelling agent in jellies recipe, which guarantees the typical chewy texture, is gelatin obtained from pig and/or bovine skin. For this reason, a detailed thermo-rheological characterization on gelatin gels is performed. We investigate the sol-gel transition of aqueous pig-skin gelatin solutions at different concentrations and temperatures. In particular, we characterize the isothermal gelation kinetics close to the critical melting temperature. The time evolution of the moduli is analyzed at a specific fixed frequency and at various temperatures and concentrations. The isothermal study allows to evaluate the gel time and to determine its dependence on concentration and temperature. Furthermore, the effects of co-solutes on aqueous gelatin solution is evaluated. Such a analysis allows to understand the key role that sugars play in the molecular architecture of gelatin gels. We demonstrate that co-solutes enhance the gelation phenomenon leading to both stronger gel elasticity and improved thermal stability. According to results obtained from gelatin gels, a hydrocolloidal mixture composed by k-carrageenan and xanthan gum is proposed as possible replace for gelatin in jellies. Moreover, the thermo-rheological behavior of aqueous solutions of k-carrageenan and xanthan is studied both in the presence and in the absence of co-solutes. From this analysis we can demonstrate that, also in this case, co-solutes exhibit a stabilizing effect, improving the mechanical properties of the resulting gel.

Downloads

Actions (login required)

View Item