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.