The effect of drying methods on the energy consumption, bioactive potential and colour of dried leaves of Pink Rock Rose (Cistus creticus)

Abstract

This study aimed to investigate the changes in the total polyphenolic content and antioxidant properties after subjecting Pink Rock Rose ( Cistus creticus ) leaves to three different drying procedures, including convection drying (CD) at 40, 50 and 60 °C; vacuum-microwave drying (VMD) at 240 W microwave power; and combined drying consisting of convective pre-drying at 50 °C followed by vacuum-microwave finish drying at 240 W microwave power (CPD-VMFD). The total polyphenolic content and antioxidant properties (DPPH, ABTS) of leaves subjected to these three drying methods were spectrophotometrically determined. The results show that convection drying at 40 °C and vacuum-microwave drying yielded dried leaves with the highest bioactive potential in terms of the total polyphenol content and antioxidant activity, with the highest and lowest values of final specific energy consumption, respectively. The lowest bioactive potential was found in a product dried at 60 °C, which can be attributed to the possible degradation or changes in polyphenol structures under high temperatures. During the combined treatment (CPD-VMFD), most of the moisture was efficiently removed from the raw material by CPD, whereas the time of drying was significantly reduced by the application of VMFD. Combined drying CPD-VMFD is most suitable for industrial applications as it produces dried leaves with a bioactive potential that is only slightly lower than that achieved with VMD while providing a high-throughput capacity relative to operating costs.

Effect of Fertilization in Selected Phytometric Features and Contents of Bioactive Compounds in Dry Matter of Two Varieties of Basil (Ocimum basilicum L.)

“…The shorter drying time of the Cistus creticus herb by the CPD 40 °C-VMFD 240 W method compared to traditional CD convection drying at 40, 50 and 60 ° C was noted by Stępień et al [19]. In addition, the use of the combined drying method CPD 40 °C-VMFD 240 W compared to convective CD drying at 40 ° C, the results showed reduced energy consumption by 56.7% per g of dried raw material [19]. The dry material obtained from Genovese basil, treated with organic and mineral fertilizer, reached the final moisture level of about 2% after 272 and 276 minutes, respectively.…”

“…The samples of raw common basil, each 100 g ± 1 g, were subjected to the combined method in three technological repetitions. The combined convective pre-drying and vacuum-microwave finish drying method (CPD-VMFD) [19] involved pre-drying of the samples for 3 h in a convection dryer at a temperature and airflow of 40 • C and 0.8 m s −1 , respectively. Subsequently, additional drying was performed in a vacuum-microwave dryer at a power of 240 W magnetrons in a rotating drying chamber until the sample mass measurement (0.05 g accuracy) showed a weight value corresponding to the assumed final moisture content of 5% wb.…”

“…The method uses microwave radiation, as an additional source of heat, in order to reduce the duration of the drying process, and consequently to improve the quality of the final product [20]. The shorter drying time of the Cistus creticus herb by the CPD 40 • C-VMFD 240 W method compared to traditional CD convection drying at 40, 50 and 60 • C was noted by Stępień et al [19]. In addition, the use of the combined drying method CPD 40 • C-VMFD 240 W compared to convective CD drying at 40 • C, the results showed reduced energy consumption by 56.7% per g of dried raw material [19].…”

Effects of infrared freeze drying on volatile profile, FTIR molecular structure profile and nutritional properties of edible rose flower (Rosa rugosa flower)

“…These findings were consistent with the results of the volatile profile analysis. The difference may be a result of the loss of heat sensitive flavor compounds and the formation of novel volatile compounds in R. rugosa flower under various drying conditions 34 …”

Bioactive Compounds, Vitamins and Minerals Composition of Freeze-dried Grewia asiatica L. (Phalsa) Pulp and Seed Powder

“…Phalsa is a darkcolored fruit, and this dark purple color of phalsa is attributed to the presence of anthocyanins Singh et al (2009). Hot air drying of materials causes degradation of important flavors and bioactive compounds, as reported by Stepien et al (2019). A higher concentration of bioactive compounds in freezedried phalsa as compared to fresh could be attributed to the greater extraction efficiency.…”