## 3 Results
### Unit Energy Consumption  
The unit energy consumption during ultrasound assisted-extraction of polyphenols ranged from 0.38 to 2.63 kJ\(\cdot\)mg\({}^{-1}\) GAE\(\cdot\)g\({}^{-1}\) dry matter varying according to the experimental conditions (Figure 5). The highest unit energy consumption was obtained for a particle size of 0.75 mm, an extraction time of 15 min and an ultrasonic intensity of 8.6 W\(\cdot\)cm\({}^{-2}\), while the lowest value in the case of particle size of 0.75 mm, time of 5 min and an intensity ultrasound of 1.6 W\(\cdot\)cm\({}^{-2}\). Figure 5: _Cont._  
Given the \(p\)-values of each equation coefficients, it could be confirmed that three linear terms (\(X_{1}\), \(X_{2}\) and \(X_{3}\)), two quadratic terms (\(X_{1}\)\({}^{2}\), \(X_{2}\)\({}^{2}\)) and two interactive terms (\(X_{1}\)\(X_{3}\) and \(X_{2}\)\(X_{3}\)) were significant and indicate the pattern of the interactions between the tested variables. However, the quadratic terms of particle size and time of extraction demonstrated positive correlations, showing that the rise in the magnitude of these variables could reduce the unit energy consumption to a certain value. The use of elevated particle size and time of extraction above the range studied may considerably increase the specific energy. The particle size was the variable that most significantly influenced the unit energy consumption, possibly due to the increased access of the solvent to the soluble substances contained in the solid matrix. The higher level of disintegration provides better accessibility of the solvent to the internal structures of tissues. The impact of the degree of fragmentation of the raw material on the unit energy inputs was also observed in the case of obtaining other plant ingredients [55]. During the extraction of soluble substances from dried carrots, the highest energy inputs were found for the raw material fraction with a medium degree of comminution. The interaction between the degree of fragmentation and the extraction time and the intensity of ultrasound also played a significant role. In the case of low values of these variables, the influence of the fragmentation degree on the size of unit energy inputs was not observed, in the case of higher values, the influence of the fragmentation degree on unit energy inputs was significant. In general, an increase in the extraction time and the intensity of ultrasound leads to an increase in the unit energy inputs per unit of active substance extracted. During the extraction of polyphenols from hawthorn berries, [PERSON] [33] observed that the unit energy inputs varied from 0.26 to 3.21 kJ\(\cdot\)mg\({}^{-1}\) GAE\(\cdot\)g\({}^{-1}\) dry matter, which is comparable with the results obtained in the present experiment. During the extraction of anthocyanins under the same conditions, the unit energy inputs varied in the range from 32.56 to 208.76 kJ\(\cdot\)mg\({}^{-1}\) Cy3-GE\(\cdot\)g\({}^{-1}\)d.m. [PERSON] [56] needed 0.246 kJ to obtain 1 mg caffeine while 2 kJ\(\cdot\)mg\({}^{-1}\) caffeine were reported by [PERSON] [57]. Such large differences in the values of unit energy inputs are caused by the active substance content in the tested raw material. Additional factors affecting energy efficiency are liquid-solid ratio, kind of solvent, water-alcohol ratio and working mode of the ultrasonic processor. Figure 5: Response surfaces for the unit energy consumption ( kJ\(\cdot\)mg\({}^{-1}\) GAE\(\cdot\)g\({}^{-1}\)) in hemp showing the effect of (**a**) time and size particle, (**b**)size particle and intensity, (**c**) intensity and time. The mechanism of an increase in unit energy inputs with an increase in the extraction time and ultrasound intensity was explained in the work of [PERSON] et al. [33]. The main reason for the increase in unit energy consumption is the depletion of the extracted substance with the extension of the extraction time.