## 3 Results and Discussion
### Multi-Objective Optimization
Assuming the mentioned accuracy of \(T_{d}\) and \(v_{d}\) setting, drying at T\({}_{d}\) = 55.0 \(\pm\) 0.5 \({}^{\circ}\)C and \(v_{d}\) = 1.0 \(\pm\) 0.02 m/s (parameters from ID 134) allows for obtaining _Echium amoneum_ petals with the following parameters: TAC\({}_{\text{loss}}\), TFC\({}_{\text{loss}}\), A\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\), CD, EC: 35.8%, 10.2%, 42.1%, 40.4%, 38.1, and 499.4 MJ/kg, respectively (average values for mentioned ranges of \(T_{d}\) and \(v_{d}\)). For TFC\({}_{\text{loss}}\) Pareto front (Figure 4c) solutions for ID69 (TFC\({}_{\text{loss}}\) = 8.6% and EC = 456.2), ID 92 (TFC\({}_{\text{loss}}\) = 9.4% and EC = 434.8), ID109 (TFC\({}_{\text{loss}}\) = 10.3% and EC = 420.2 MJ/kg), and ID116 (TFC = 11.3% and EC = 410.3 MJ/kg) are indicated. These solutions are obtained for the following drying process parameters: air drying temperature 53.35, 53.94, 54.51 and 55.12 \({}^{\circ}\)C, and air-drying velocity 1.00 m/s. However, for these solutions, EC is 1.6, 1.6, 1.5 and 1.5, CD is 2.0, A\({}_{\text{loss}}\) is 1.0, TAC\({}_{\text{loss}}\) is 2.1, 2.4, 2.6 and 2.8, TFC\({}_{\text{loss}}\) is 1.3, 1.4, 1.5 and 1.7, and TPC\({}_{\text{loss}}\) is 1.8, 1.8, 1.7 and 1.7 times higher than its minimum values. Assuming the mentioned accuracy of \(T_{d}\) and \(v_{d}\) setting, drying \(v_{d}=1.0\pm 0.02\) m/s (parameters from IDs: 69, 109--those are better from the TAC\({}_{\text{loss}}\) and TEC\({}_{\text{loss}}\) point of view) allows for obtaining _Echium anoneum_ petals with the following parameters: TAC\({}_{\text{loss}}\), TEC\({}_{\text{loss}}\), A\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\), CD, EC: 35.0%, 9.0%, 39.1%, 39.1%, 38.3, and 445.5 MJ/kg, respectively (average values for mentioned ranges of \(T_{d}\) and \(v_{d}\)). For TPC\({}_{\text{loss}}\) Pareto front (Figure 4e) indicates solutions ID94 (TPC\({}_{\text{loss}}\) = 25.2% and EC = 445.5 MJ/kg), ID107 (TPC\({}_{\text{loss}}\) = 26.0% and EC = 410.1 MJ/kg), ID 117 (TPC\({}_{\text{loss}}\) = 27.0% and EC = 348.6 MJ/kg) and ID113 (TPC\({}_{\text{loss}}\) = 27.6% and EC = 364.9 MJ/kg). These solutions are obtained for the following drying process parameters: air-drying temperature 59.76, 59.82, 59.98 and 59.86\({}^{\circ}\)C, and air-drying velocity 0.54, 0.53, 0.51 and 0.52 m/s, respectively. However, for these solutions, EC is 1.6, 1.5, 1.3 and 1.3, CD is 2.0, 2.0, 1.9 and 1.9, A\({}_{\text{loss}}\) is 1.3, 1.3, 1.2 and 1.2, TAC\({}_{\text{loss}}\) is 2.4, 2.5, 2.8 and 2.7, TEC\({}_{\text{loss}}\) is 4.4, 4.3, 4.2 and 4.2, and TPC\({}_{\text{loss}}\) is 1.2, 1.2, 1.3 and 1.3 times higher than their minimum values. Due to the very small differences between the individual values of drying parameters obtained and the lack of such precise settings, it can be assumed that the best parameters due to energy savings are following: \(T_{d}\) = 60.0 \({}^{\circ}\)C and \(v_{d}\) = 0.52 m/s. Assuming the mentioned accuracy of \(T_{d}\) and \(v_{d}\) setting, drying at \(T_{d}\) = 60.0 \(\pm\) 0.5 \({}^{\circ}\)C and \(v_{d}\) = 0.52 \(\pm\) 0.02 m/s can obtain _Echium anoneum_ petals with the following parameters: TAC\({}_{\text{loss}}\), TEC\({}_{\text{loss}}\), A\({}_{\text{loss}}\), TPC\({}_{\text{loss}}\), CD, EC: 44.0%, 28.3%, 47.7.1%, 29.0%, 36.8, and 349.1 MJ/kg, respectively (average values for mentioned ranges of \(T_{d}\) and \(v_{d}\)). It can be stated that there is no unequivocal solution to the optimization problem written by Equation (9). The solutions relate to the _Echium anoneum_ petals drying parameters at which the lowest values of individual quality parameters, EC or CD, sometimes groups of the parameters were obtained. However, CD was always conflicting with other quality parameters (see Figure 4b), so this parameter was omitted in further considerations. The optimization results show (Figures 5 and 6) that A, TAC, TFC are interrelated. Figure 6 shows the four solutions for the optimization task.