THE CRUDE TANNIN EXTRACTION FROM WOOD SCRAP WASTES FOR PROLONGING THE SHELF LIFE OF LITCHI FRUITS

Abstract

Waste from wood scraps is an important problem in areas of wood handicraft performed. The purposes of this research were to study the optimum condition for crude tannin extraction from those wastes and usage them for prolonging shelf life of litchi fruits. Various chemicals used for the extraction included distilled water, 95% ethanol, 8% sodium carbonate and their combinations. The proportion between wood scrap per solvent were 1:10 or 1:20 g.mL-1 and extraction temperature were 70, 80 or 90°C. The basic chemical characteristics of the extracted tannin were tested. Quantification of tannin was performed by spectrophotometer. The results found that optimum solvent was 95% ethanol with proportion at 1:10 g.mL-1 and 80°C extracted temperature, which gave the maximum amount of tannin (12.34 mg.g-1 dry weight). Then, crude tannin was tested for the in vitro fungicidal effect to pathogenic fungi isolated from litchi fruits. The PDA medium containing crude tannin at different concentrations including; 0, 0.1, 0.2 and 0.4 % were tested in comparing to 0.1% benomyl fungicide. The result was found that PDA containing 0.2 and 0.4% of extracted tannin significantly (P≤0.05) inhibited growth of fungal mycelium better than 0 and 0.1 % but still lower than benomyl fungicide. The in vivo test with litchi fruits by soaking the fruits in various concentrations of crude tannin; 0, 0.1, 0.2 and 0.4%, compared to 0.1% benomyl fungicide was found that 0.2% tannin could extend the shelf life of litchi fruits better than other concentrations but its efficiency was still lower than benomyl fungicide.