Physicochemical properties of lacquer berries and decolorization of lacquer wax by physical adsorption and UV irradiation

Abstract

Physicochemical properties of No.1 - No.6 lacquer berries were investigated from different origins. The Japan Showafuku (No.1) was the best cultivar of Rhus succedaneum, the size of the berry of it was near 3 - 4 folds, which was bigger than the Chinese cultivars (No.4 - No.6) of Rhus vernicifera et al. It had more than 5% ~ 10% of lacquer wax in pericard, and contained less than 6% - 8% of lacquer oil in seed. No.1 had lower acid value (A.V) and iodine value (I.V); the key factors for this were cultivar and its growing environment. The principal constituents of lacquer waxes of No.1 - No.6 were triglycerides of fatty acids with total saturated fatty acids (TSFA) of 75% - 82.7%, total unsaturated fatty acids (TUSFA) of 15.1% - 20%, and total dibasic acids (TDBA) of 5%. The CIEL a b system and Hunter whiteness formula were used to evaluate the bleaching effect on lacquer wax by physical adsorption and ultraviolet (UV) irradiation. The optimal conditions of physical decoloration were determined for activated carbon: kieselguhr = 3:2 (g/g) as adsorbent, a ratio of 1:20 (g/mL) for lacquer wax to petroleum ether, bleaching 30 min at 80?C. UV light achieved a good bleaching effect irradiated at 60?C for 60 hrs. UV irradiation definitely changed relative contents of fatty acids, TUSFA and TDBA decreased from 19.617% to 11.022% and 4.379% to 2.017% respectively, while TSFA could be raised from 76.462% to 86.077%, however, the mechanism of UV irradiation was still unclear and should be investigated in the future.