## 3 Processing and Extraction
### Ultrasound Assisted Extraction
#### 3.2.1 Polyphenolic Compounds  
[PERSON] et al. (2017) examined raspberry pomace extraction using the UAE method and compared it to conventional maceration. UAE was conducted in an ultrasonic cleaner for 20 min at 50 \({}^{\circ}\)C and 50 kHz with acidulated methanol as a solvent. The obtained results showed that measured TPC, TFC and TAC were all significantly increased when UAE was used. It led to levels of 27.79 mg GAE/L of extract, 8.02 mg QE/g of pomace and 7.13 mg CGE/L of extract for TPC, flavonoid content and anthocyanin content, respectively. In addition, AA measured in FRAP and DPPH assays was higher in extracts treated with ultrasound. The values obtained for FRAP and DPPH were 1002.72 \(\upmu\)mol FE/L of extract and 567.00 \(\upmu\)mol TE/100 g of pomace, respectively. Ellagic acid was detected by HPLC as the most abundant polyphenol. [PERSON] et al. (2018) conducted UAE of polyphenols from blueberry wine pomace. Before extraction, the pomace was stored as freeze-dried material. In this paper, it was summarized how individual parameters of UAE--sonication time, solid-liquid ratio, solvent type, temperature and pH--affected the quality of extracts. Qualitative parameters consisted of TPC, TFC, TAC and AA. The time of extraction significantly affected only TAC, which values were significantly higher in the case of a 90 min run. Solid-liquid ratio was a factor determining changes in all measured parameters. With water used as a solvent, TPC, TFC and TAC were highest for the lowest value of the solid-liquid ratio--1/40. A solid-liquid ratio of 50% ethanol at the lowest level of 1/20 resulted in the highest AA, TPC and TAC in extracts. However, TFC did not follow that trend and the highest values were reached with a 1/15 ratio. In addition, concentrations for all of the compounds, as well as the AA value, were significantly higher when 50% ethanol was used in UAE. Ethanol concentration was also a parameter affecting bioactive compound yield and AA of extracts. The most effective concentration was 50% (\(v/v\)) ethanol in water. The lowest TPC, TFC, TAE and AA values were obtained using the highest concentration of ethanol--90% (\(v/v\)). pH determined significantly TPC, TAC and AA, and for TPC and AA, pH 8.3 was the most effective; however, it resulted in decreased TAC, which was highest with pH 3.3. The temperature set at 60 \({}^{\circ}\)C resulted in significantly increased TFC and AA but decreased TPC, for which a temperature set at 20 \({}^{\circ}\)C was the most preferable. TAC was not significantly affected by temperature. The anthocyanin profile was specified by HPLC. In both water and ethanolic extracts, the most abundant compound was malvidin and subsequently delphinition, peturidin and cyanidin. [PERSON] et al. (2019) described UAE optimization using RSM. The experiment was held under constant conditions of frequency 20 kHz, S-L ratio 1:24 and a temperature of 4 \({}^{\circ}\)C at the beginning of the process and measured as 25 \({}^{\circ}\)C at the end. Variable parameters were the amplitude of ultrasounds, in a range of 80-90%, and the time of extraction, in a range of 10-15 min. Mathematical analysis revealed an amplitude and time of 91% and 15 min, respectively, as the most beneficial parameters for TPC, TAC and AA extracts at dm basis. Predicted values were 1200 mg GAE/100 g TPC, 380 mg/100 g TAC and 6300 \(\upmu\)mol TE/100 g AA in an ABTS assay and 9600 \(\upmu\)mol TE/100 g in a DPPH assay. The experimental values obtained at optimum UAE conditions were: 1201.23 mg GAE/100 g, 379 mg/100 g, 6318 \(\upmu\)mol TE/100 g and 9617.22 \(\upmu\)mol TE/100 g for TPC, TAC, AA (determined by ABTS) and AA (determined by DPPH), respectively. The UAE method was compared to conventional SLE with use of both water and ethanol. UAE yielded the highest values for TPC and AA in both assays. However, TAC in the extract obtained by UAE was not significantly different from the TAC of the extract obtained by SLE with water and was significantly lower compared to the result for SLE with ethanol.