Green Extraction Process of Bark Tannin from Maritime Pine

The rising demand for plant-extracted tannins emphasizes the need for eco-friendly and cost-effective extraction methods. Although classical water bath extraction can boost tannin yield with high temperatures and long times, it also has drawbacks, such as tannin auto-condensation, thermal decomposition, impurities, and oxidation. This study explored various extraction methods for maritime pine bark tannin, optimizing conditions. Classical water bath, Soxhlet, ultrasound-assisted, and microwave-assisted extractions were tested with varying extraction solutions, solid–liquid ratios, temperatures, and times. The chemical composition of the phenolic extracts obtained after extraction was determined by the Stiasny number method, total phenolic content, and proanthocyanidin (butanol-HCl) method. Additionally, the amount of impurities in the tannin extract was determined by the DNS (dinitrosalicylic acid) reducing sugar method. FTIR spectrometry was applied to the extract powders. Advanced green extraction methods that support sustainable forestry have shown superior performance over traditional techniques for extracting tannins from maritime pine bark. In particular, microwave-assisted extraction demonstrated higher efficiency and greater stability than ultrasound-assisted extraction when using similar solvent-to-material ratios. In contrast, Soxhlet and classical water bath extractions were less sustainable, requiring larger volumes of solvents, prolonged extraction times, and higher temperatures, making them both less efficient and environmentally favorable.