Differences in Browning Index and CIELAB Coordinates of the Two Grape Drying Processes, Traditional Sun-Drying and Chamber-Drying and during the Ageing of Pedro Ximenez Sweet Wine

The color parameters during the Pedro Ximenez grape raisining, as well as the sweet wine aging process from the Montilla-Moriles grapes （Andalusia, Southern Spain）, have been studied. Drying process of grapes was carried out by means of the traditional sun-drying method and an alternative chamber-drying method under 50℃. Chamber-drying allows shorter drying time and select grapes at a higher ripening degree. During raisining grape musts decreased in hab （hue angle） and increased in Cab （chroma）. In comparative terms, the final values of hue were virtually identical in both types of drying, although differences were found in the final values of chromaticity, being lower in the chamber-drying method. Changes in the color parameters during aging were compared in commercial wines with different aging systems and without aging. Likewise, as a reference of traditional wine aging system, the color changes in wines with four aging degrees were also studied. Regarding to the commercial wines studied, it can be pointed out the wine aged without blends for 4 years significantly differed in the values of hab and C＊ab of the remaining wines, which show more similar values among them and in the data obtained for the wines aged by the traditional aging system.

Characterization and evaluation of UV-irradiation aging of urushi by micro-UV/Py-GC/MS system

Lacquer is the main raw material of lacquerware,while UV-irradiation is an important factor leading to its aging.In order to investigate the aging behavior of urushi lacquer film under UV-irradiation,and to propose parameters that can be used to evaluate its aging degree,the micro-UV/Py-GC/MS system has been applied in the present work to enrich and identify volatile products released by urushi film during aging on the one hand,and to investigate micro-amount and conventional urushi films with different aging degrees on the other hand,in addition,representative historical samples have also been investigated.Volatile products released by urushi film demonstrate that during UV-irradiation,polysaccharides wrapping urushiol polymer would be first degraded to generate furans and alcohols,and then urushiol polymer would undergo photo-oxidation and break of molecular chain,mainly generating oxidation products including aldehydes,organic acids,and ketones,as well as a small number of alkyl benzenes and hydrocarbons.Py-GC/MS analysis of micro-amount urushi films with different aging degrees indicates that UVirradiation is more destructive to aliphatic chains in urushiol polymer,but it also can accelerate the polymerization of microamount urushi film.Py-GC/MS analysis of conventional urushi films indicates that with the increase of aging degree,the total chromatographic peak area ratio of hydrocarbons to benzene derivatives gradually increases,the peak area ratio of 3-pentadecenyl-catechol to 3-pentadecyl-catechol gradually decreases,and the peak area ratio of aging products of urushiol to 3-pentadecyl-catechol gradually increases.The above parameters were further used to evaluate the aging degree of two urushicontained samples separately collected from the surface and interior of a carved lacquer panel in the Forbidden City,and evaluation results are in accord with the natural aging law and further verify the reliability of the proposed parameters.Research results of the present work can lay a foundation for the in-depth study of the UV-irradiation aging mechanism of urushi.