Combination of Pulsed Electric Field and Ultrasound in the Extraction of Polyphenols and Volatile Compounds from Grape Stems

Abstract

Increasing the yield of extraction of bioactive compounds from plants is of high importance. Grape stems are widely discarded during the wine-making process, despite their high content in many valuable compounds. The aim of this work was to examine whether the use of pulsed electric field (PEF) treatment of the stems could increase the yield of polyphenol and volatile compounds in the extracts. For this reason, a relatively low-energy consuming PEF process was employed (low-electric field strength, 1 kV/cm) for a short time (30 min) at the grape stems. In addition, the effect of different solvents during this pretreatment step was examined. With the use of Folin–Ciocalteu assay, the extracts were compared with the respective control samples (not pretreated with PEF). Moreover, extracts were prepared to assess whether changes occur to the volatile profile of the extracts. The results were conclusive that not only PEF can increase the yield of polyphenols (up to 35% increase recorded), but also that the solvent used during PEF pretreatment can affect the process. Furthermore, a 234% increase in the total content of volatile compounds was recorded, when PEF was used as a pretreatment step. Therefore, the combination of PEF and ultrasound-assisted extraction is highly promising to obtain grape stem extracts with a higher content of bioactive compounds.

Recent advances in combined Avant-garde technologies (thermal-thermal, non-thermal-non-thermal, and thermal-non-thermal matrix) to extract polyphenols from agro byproducts

“…Görgüç et al [ 201 ] applied PEF + UAE to extract polyphenols from the Rosemary byproduct ( Table 3 ) and reported that UAE + PEF (2.97 mg GAE/g) was 1.5× higher than UAE alone. Likewise, Ntourtoglou et al [ 202 ] extracted polyphenols from grape stems ( Table 3 ) and reported that PEF-UAE augmented the TPC extraction (35%) compared to the control (PEF alone). This could be explained by the combinative effect of the electroporation by (PEF) and the cavitation effect by ultrasound that cleaves the cell membrane and allows polyphenols to be released, thus increasing the TPC yield.…”

Pulsed Electric Field Applications for the Extraction of Bioactive Compounds from Food Waste and By-Products: A Critical Review

“…Ntourtoglou et al [67] examined the potential impact of PEF pretreatment on the efficiency with UAE of polyphenols and volatile compounds from grape stems. An electric field strength of 1 kV/cm for a total duration of 30 min was used.…”

Pulsed electric field for shalgam juice: effects on fermentation, shelf‐life, and sensory quality

“…61 Turk et al 62 reported that the PEF application increased the odor density in apple juice. Intense feeling of odor depending on the improved aroma extraction with the PEF application 63 may have caused the odor score of the PEF-treated shalgam juice samples. However, statistically no difference in the odor score between the samples was observed on the 60th day (P > 0.05).…”