Novel non-invasive method for extracting proteinaceous binders from panel paintings

This paper proposed a novel method for the non-invasive extraction of proteinaceous binders from panel paintings using high-acyl (HA) and low-acyl (LA) gellan gums. The binder extraction effects of different gums on simulated panel paintings were compared and characterized in terms of extracted protein concentration, macro and micro appearance, color difference, pH, and contact angle. Then, Fourier transform infrared spectroscopy was performed to analyze the extraction mechanism. On this basis, non-invasive extraction was conducted on panel paintings with different types and concentrations of proteinaceous binders using HA gellan gums. The results showed that neither HA nor LA gellan gum significantly affected the surface color, pH, contact angle, or visual appearance of the paint layer. The protein extraction effect of gellan gum is mainly affected by pressure and concentration gradient. The HA gellan gum has a strong water retention capacity, high softness, and a more stable internal structure. Therefore, the concentration of the protein solution extracted by HA gellan gum was 2.4 times higher than that extracted by LA gellan gum, with less possibility of gel residue. Further, HA gellan gum showed a good extraction effect on different types and concentrations of proteinaceous binders. Therefore, the proposed method is expected to serve as an effective means for the non-invasive extraction of proteins from painted objects.