Sustainable vegetable tanning: Ultrasound-assisted tannin extraction of oak bark and analytical approaches to collagen-tannin interactions

Ilaria Quaratesi; Vittoria Ferrara; Ioan Călinescu; Petre Chipurici; Ioana Popa; Cristina Carşote; Pellegrino La Manna; Elena Badea

doi:10.1016/j.ijbiomac.2025.148194

Sustainable vegetable tanning: Ultrasound-assisted tannin extraction of oak bark and analytical approaches to collagen-tannin interactions

Int J Biol Macromol. 2025 Nov;330(Pt 3):148194. doi: 10.1016/j.ijbiomac.2025.148194. Epub 2025 Oct 8.

Authors

Ilaria Quaratesi¹, Vittoria Ferrara², Ioan Călinescu³, Petre Chipurici³, Ioana Popa³, Cristina Carşote⁴, Pellegrino La Manna⁵, Elena Badea⁶

Affiliations

¹ Industrial Chemistry Department "Toso Montanari", Alma Mater Studiorum-University of Bologna, Ue4 via Gobetti 85, 80129, Bologna, Italy; National Research and Development Institute for Textile and Leather, Research Institute for Leather and Footwear (INCDTP-ICPI), Strada Ion Minulescu 93, Sector 3, 031215, Bucharest, Romania.
² Department of Chemistry and Biology "A. Zambelli", University of Salerno, Via Giovanni Paolo II 132, I-84084, Fisciano, SA, Italy.
³ Faculty of Chemical Engineering and Biotechnologies, National University of Science and Technology Politehnica Bucharest, Strada Gheorghe Polizu 1-7, Sector 1, 011061, Bucharest, Romania.
⁴ Center for Research and Physical-Chemical and Biological Investigations, National Museum of Romanian History, Calea Unirii 12, Bucharest, Romania. Electronic address: cristina.carsote@mnir.ro.
⁵ Water Science and technology group (WaSTe), Department of Civil Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084, Fisciano, SA, Italy.
⁶ National Research and Development Institute for Textile and Leather, Research Institute for Leather and Footwear (INCDTP-ICPI), Strada Ion Minulescu 93, Sector 3, 031215, Bucharest, Romania; Department of Chemistry, Faculty of Sciences, University of Craiova, Calea Bucuresti, 107, Craiova, Romania; The Research Institute of the University of Bucharest, Șoseaua Panduri 90, Sector 5, 050663, Bucharest, Romania. Electronic address: elena.badea@edu.ucv.ro.

PMID: 41072693
DOI: 10.1016/j.ijbiomac.2025.148194

Abstract

Sustainable leather production has long faced the challenge of finding eco-friendly methods maintaining quality standards. This study investigates vegetable tanning with oak bark extracts obtained using eco-friendly Ultrasound-Assisted Extraction (UAE), providing a straightforward analytical approach for a better understanding of the molecular mechanisms by which these extracts stabilise the collagen-tannin interactions. Aqueous extraction of oak bark polyphenols, achieved employing a continuous UAE process, scalable for industrial use, was also boosted using very low concentrations of NaOH (0.1 to 0.5 %) or 0.25 % sulfite/bisulfite. Collagen-tannin matrices were characterized using micro-differential scanning calorimetry (micro-DSC), ATR-FTIR spectroscopy, NMR MOUSE, and thermal microscopy. Key results show that aqueous and low-alkali bark extracts stabilise collagen mainly through hydrogen bonding. Alkali and sulfonated extracts create a mixed network of hydrogen and covalent bonds, likely linked to lignin derivatives. Micro-DSC analysis revealed the highest increase in denaturation temperature, up to 11-14 °C, and a narrowing of transition peaks in collagen matrices treated with 0.2 % and 0.5 % NaOH extracts. ATR-FTIR confirmed the formation of ester bonds. NMR MOUSE results showed increased chain packing and water exclusion, linking to enhanced physicomechanical properties. Leather produced using the oak bark extracts showed hydro-thermal and mechanical resistance and structural homogeneity that match those of conventional vegetable-tanned leathers. These findings highlight the technological, commercial and environmental value of UAE-derived oak bark tannins for sustainable leather production. The approach adopted in manuscript fosters sustainability in the tannery sector by reducing the environmental impact and converting tree bark, a low-value by-product, into valuable tannins.

Keywords: Circular economy; Collagen matrix stabilization; Oak bark; Ultrasounds-assisted extraction; Vegetable tanning.

MeSH terms

Chemical Fractionation / methods
Collagen* / chemistry
Plant Bark* / chemistry
Plant Extracts / chemistry
Quercus* / chemistry
Spectroscopy, Fourier Transform Infrared
Tanning* / methods
Tannins* / chemistry
Tannins* / isolation & purification
Ultrasonic Waves*

Substances

Tannins
Collagen
Plant Extracts