Gelatin has been widely used in biomedicine due to its high biocompatibility and low cost ( Rubini et al., 2020). Therefore, different extraction processes can lead to different relative molecular weights of gelatin, as well as different physical and structural properties of gelatin ( Muyonga et al., 2004 Carvalho et al., 2008). The greater content of high relative molecular weight components corresponds to the higher gelation properties of gelatin. The gel strength of gelatin mainly depends on its molecular properties, especially relative molecular weight distribution and amino acid composition ( Gómez-Guillén et al., 2002). The viscosity of gelatin is related to its relative molecular weight, and the higher high relative molecular weight components, the higher the viscosity ( Enrione et al., 2020). The bloom number of gelatin corresponds to the proportion of α chain, and the greater the proportion of α chain, the greater the gel strength of gelatin ( Netter et al., 2020).

Corresponding to the hydrolysis methods, the isoelectric points of type-B and type-E gelatin are 4.6–5.2 and 7.0–9.0, respectively ( Gómez-Guillén et al., 2011).įunctional properties of gelatin, such as freezing strength, viscosity and gel strength, are highly associated with its relative molecular weight distribution ( Elharfaoui et al., 2007). The type-E gelatin is extracted by enzymatic hydrolysis collagen, with higher elasticity and relatively narrow relative molecular weight distribution ( Ahmad et al., 2017). The type-B gelatin is extracted by alkaline hydrolysis of collagen, with higher rigidity and wider relative molecular weight distribution. Based on different extraction processes, gelatin can be mainly grouped into type-B and type-E. In addition, there are other types of gelatin with either lower relative molecular weight or higher relative molecular weight. The relative molecular weight distribution of gelatin is mainly concentrated in about 100, 200 and 300 kg/mol, corresponding to α, β, and γ peptide chains, respectively ( Tu et al., 2015). Different preparation techniques can lead to the difference in relative molecular weight distribution of gelatin ( Sittiruk and Siriporn 2006 Ahmad et al., 2018). Gelatin is a kind of natural macromolecular compound, which belongs to the hydrocolloid family and can be extracted from skin, bone and connective tissues of animals through partial hydrolysis of collagen ( Jridi et al., 2013 Dara et al., 2020). Finally, the addition of SO 4 2− in gelatin film was performed to confirm the dominant effect of component compared to pI on swelling behavior of gelatin films. Furthermore, with the pH of solution environment far from the isoelectric point (pI) of gelatin films, the swelling ratios were found to increase remarkably, which is due to electrostatic repulsion expanding the pore size of peptide chains. Based on analyzing relative molecular weight distribution of type-B and type-E gelatins, the more widely distributed relative molecular weight is the key attribution for enabling easier diffusion of water molecules inside the porous channels of peptide chains.

In the drug releasing simulation, type-B gelatin capsules also showed a faster collapse rate than type-E gelatin capsules. The results showed that the swelling ratio of the gelatin film extracted by alkaline hydrolysis of collagen (type-B) in a range of pH environments was higher than the one extracted by enzymatic hydrolysis collagen (type-E). The swelling behavior of gelatin films with different extraction processes are investigated. 2Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing, China.1School of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing, China.Fangqi Ji 1 Wei Zhou 1* Ze Zhang 1 Bing Zhang 2*

Gelatin leaves vs powder