Drying Operation Effects on the Pigments and Phytochemical Properties of Rose Cultivars

Roses are flowers which contain various phytochemicals and have been used for food and medicinal purposes in many countries. Materials, including flowers, are available for limited periods when plants can be cultivated.

To evaluate the quality of rose petals on the basis of cultivars and drying methods, chromaticity, phytochemical contents, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity.

Petals of three rose cultivars were dried by hot air drying (HD) and freeze drying (FD). Subsequently, the chromaticity and the contents of pigment, total flavonoids, and ascorbic acid, and DPPH radical scavenging activity were analyzed.

The total color difference (△E)values of rose red (RR, Calypso) and rose orange (RO, Lambada) were low in FD. In contrast, in rose yellow (RY, Ileos), there was no significant difference in chromaticity regulation regardless of the drying methods. The pigment contents were generally increased by drying. The carotenoid content in the RR and anthocyanin and carotenoid contents in RO were higher in FD than in HD. The drying operations increased the flavonoid and ascorbic acid content and antioxidant activity in roses, but the difference between the drying methods was not significant. Correlation coefficient analysis revealed ascorbic acid and anthocyanin to have a high positive correlation (r = 0.843), followed by flavonoid and DPPH radical scavenging activity.

This study showed that the drying operations increased the flavonoid and ascorbic acid contents, and the chromaticity and pigment content of some cultivars was higher in FD.

Comparison of the color change, phytochemical content, and antioxidant activity by the drying methods (FD and HD treatment) in the three rose cultivars with red, orange, and yellow petals showed the increased phytochemical contents and antioxidant activity after drying, and chromaticity and pigment content were more stable and higher in FD.