Tissue engineering is a largely researched field to which scientists are paying more and more attention. It enables the regeneration of damaged tissues and organs, reducing the need for transplants and donors. Decellularized extracellular matrix (dECM) is used in tissue engineering because it provides a natural substrate that supports tissue regeneration, retaining biochemical and biomechanical factors necessary for cell growth. Also, it reduces the risk of immune rejection because it does not contain cellular components that could cause an immune reaction. Decellularized extracellular matrix hydrogels combine the biocompatibility and natural bioactivity of dECM with the mechanical properties of hydrogels, enabling optimal support for cell growth and differentiation. The detergent sodium laureth sulfate (SLES) was used to decellularize the liver tissue. Decellularized samples were additionally treated with ultrasound for 1, 2, 4, 8 and 16 hours. The biological components of DNA and collagen were quantified with such samples. Differential scanning calorimetry was also performed to determine the thermal stability of proteins. Prepared dECM hydrogels were characterized by measuring the change in absorbance over time to gain insight into gelation kinetics and by Fourier transform infrared spectroscopy (FTIR) to identify and confirm the presence of specific biochemical components within the hydrogel. Based on the research, it can be concluded that the decellularization was successful, since the quantification showed a significant decrease in the DNA content, but also a high collagen content. The best values are shown by the sample SLES 0.5b 8h, which is also confirmed by the FTIR analysis, so this sample has the potential to be considered in further research since it has satisfactory gelling kinetics and the maximum denaturation temperature.