Xuan Li,Xinye Wu,Jinfeng Bi,Xuan Liu,Xiao Li,Chongting Guo
Polyphenols are closely related to the nutritional value , flavor, and color of dried apple products. In present work, the correlation of polyphenol accumulation with apple slices browning in hot air drying (65 °C, 2 m/s air velocity) process was investigated. Polyphenols composition were distinguished in different apple varieties, among which chlorogenic acid, epicatechin were the most abundant constitutes, accounting for 44.47–75.45 g/100 g, 30.31–35.16 g/100 g of total polyphenols respectively in apple flesh. Browning characteristic distribution of 7 varieties dried apple in PCA analysis model were similar to their fresh counterparts. The average browning degree were 22.31 and 6.72 in dried and fresh apple slices respectively, revealing that hot air drying treatment accelerated and extended the effects of polyphenol enzymatic browning process. High chlorogenic acid and/or catechin content induced redness value ( a* value) variation, while lower total polyphenol content and higher polyphenol diversity mainly induced brightness ( L* value) and yellowness ( b* value) variation in drying process. Specifically, in Fuji apple slices, quercetin-3-O-galactoside significantly correlated to L* variation (r = 0.838, **P < 0.01), while catechin, chlorogenic acid, phlorizin successively contributed to the variation of a* (r = 0.877, 0.906, 0.848, **P < 0.01) and b* (0.919, 0.953, 0.906, **P < 0.01). These results would be the reference for predicting and controlling the color quality of dehydrated apple products by polyphenol content and composition.
In order to develop novel anti-browning agents with both antioxidant and anti-tyrosinase properties, a series of N -caffeoyl amino acid methyl esters were designed and synthesized. Most of the synthesized compounds exhibited superior scavenging activities against DPPH radicals and ABTS cation radicals compared with caffeic acid and L-ascorbic acid. The kinetics analysis of radical scavenging for both DPPH and ABTS radicals by N -caffeoyl phenylalanine methyl ester ( 3a) suggested that the scavenging processes may follow second-order reaction kinetics. Additionally, among the compounds prepared, N -caffeoyl cysteine methyl ester ( 3o) exhibited stronger inhibitory effect on tyrosinase than kojic acid and the inhibition type was mixed. Molecular docking studies further elucidated that compound 3o binds to tyrosinase with histidine residues in the active pocket. Anti-browning experiments confirmed that the browning rates of apple slices and apple juice treated with compound 3o were significantly reduced, showing a stronger anti-browning effect than kojic acid. In conclusion, compound 3o has potential applications as an anti-browning agent.
Jun Wang,Yuxian Chen,Hui Wang,Shuyao Wang,Zina Lin,Lili Zhao,Huaide Xu
The impacts of ethanol pretreatment and blanching on moisture transfer, microstructure, and nanostructure of cell-wall polysaccharides of apple slices were studied. The physicochemical properties, namely, color, rehydration, and antioxidant capacity were also evaluated. The results corroborated that the use of ethanol and blanching reduced drying time 45–60% and 21–42% at various drying temperatures (50, 60, 70, and 80 °C), respectively, compared to controls. Ethanol loosened the cell wall structure, thereby reducing the internal resistance of moisture diffusion, and the changes in cell wall structure caused by blanching were mainly due to the β-elimination degradation of pectins. Both samples of ethanol pretreatment and blanching possessed lower browning index and higher antioxidant capacity compared with the untreated ones. Overall, ethanol pretreated products exhibited the shortest drying time, less color change and higher antioxidant capacity. These results provide new insights on possible mechanisms about ethanol pretreatment and blanching to improve drying.
危险品化学品经营许可证（带存储）