Ultrasonic Extraction of Active Compounds from Grape and Wine By-Products

Grapes (Vitis vinifera), vine and wine by-products are rich in polyphenols and other bioactive substances, which are valuable compounds for the production of medicinal and nutritional supplements. Ultrasonic extraction allows for the simple and highly efficient isolation of grape- and vine-derived compounds (e.g, grape pomace, seeds, leaves, stems, lee). Ultrasound-assisted extraction is fast, reliable and excels other extraction methods by higher yields, milder extraction conditions, shorter extraction time and lower cost.

Ultrasonic Extraction of Phytochemicals from Grape and Vine

By-products from vineyards and the wine-making process include grape pulp, pomace (skins and seeds), lees, grape leaves, stems, and cane, which make up to 30−40% w/w solids, which are mostly discarded unused as waste. Discovering the richness of polyphenols and other bioactive compounds in these grape and wine by-products, the industry is increasingly using these plant-based materials to produce valuable extracts. Resveratrol, anthocyanidins, proanthocyanidin, quercitin and other substances found in grapes and vine (Vitis vinifera) are already widely consumed as medicinal and nutritional supplements. As source of health-promoting compounds, extracts from Vitis vinifera by-products are used in the pharmaceutical and food industries, whilst at the same time supporting sustainable agriculture. Ultrasonic extraction facilitates the release of the bioactive compounds from grape and grape by-products. Ultrasound-assisted extraction is an long-time established extraction technique used for pharmaceutical and food compounds. It gives very high extract yields within a short extraction procedure and works with any solvent (e.g., water, ethanol, isopropanol, hexane etc.)

Ultrasonic Extraction of Polyphenols from Grape Seeds

Grape seeds are rich in proanthocyanidins and are therefore a great source for producing proanthocyanidin extracts for medicinal and nutritional supplements. Thilakarathna and Rupasinghe (2022) could demonstrate the superior efficiency of ultrasonication under controlled elevated temperatures, which resulted in higher proanthocyanidin yields and significantly shorter extraction time (ultrasound 53 min. vs conventional solvent extraction 150 h!).
The introduction of heat and ultrasonication significantly reduced the extraction time (sonication time of 53 min) and aqueous ethanol requirement (10.14:1 v:w) while considerably increasing the PAC yield (16.1 mg CE/g FW Vs. 26.6 predicted mg CE/g FW). The final optimum conditions were 47% ethanol, 10:1 s:s ratio (v:w), 53 min sonication time, and 60◦C extraction temperature.

Efficient Grape Leaf Extract Production Using Sonification

The leaves of the common grape vine (Vitis vinifera) are rich in reseveratrol, anthocyanidins, quercetin, isoquercetin as well as many other bioactive compounds, which are subministered often in extract form for medicinal and health purposes.
Ultrasonic extraction has been shown to give high yields of full-spectrum extract from grape leaves, thereby making the extraction process very efficient. Aqueous ethanol has been demonstrated as preferable solvent for grape vine extracts as it has excellent dissolving capacity for the target molecules and has no toxicity. The extraction process using ultrasonics takes only a few minutes and can be run in batch process as well as in continuous flow-through mode.
For instance, ultrasonically extracted resveratrol from grape leaves can be purified using a column of mesoporous carbon, which improves the resveratrol purity from 2.1 to 20.6%. (cf. Sun et al., 2018)

Ultrasonic Stilbenoid Extraction from Grape Stems

The ultrasonic extraction protocol of Piñeiro et al. (2013) results in high recovery of stilbenes such as trans-resveratrol, ε-viniferin, piceatannol, and vitisin B, which are mostly present in grape canes and in grape stems.

Graphic abstract of the study for ultrasonic stilbenoid extraction from grape stems.
(Study and picture: Piñeiro et al., 2013)

With the ultrasonicator UP200S (200W, 24kHz), the main stilbenoids found in grape stems can be extracted in 15 min, using 75°C as the extraction temperature and 80% ethanol as the extraction solvent, and no cleaning step with organic solvent is needed. The optimized method allowed for the simple and efficacious analysis of stilbenoid content from 22 grape stem samples.

Main effects plot on the mean recovery (area 10.000−1) by ultrasonic extraction using the UP200S applying various parameters: piceatannol (a), trans-resveratrol (b), ε-viniferin (c), and vitisin-B (d).
(Study and graphs: Piñeiro et al., 2013)

HPLC-DAD chromatogram corresponding to the stilbenoid enriched reference extract.
(Study and graphs: Piñeiro et al., 2013)

High-Performance Ultrasonic Processors for Grape and Vine Extraction

Hielscher Ultrasonics extractors are well established in the field of botanical extraction, no matter what plant materials or solvent is used. Extract producers – both, exclusive boutique extract manufacturers as well as large-scale mass producers – find at Hielscher‘s broad equipment range the ideal ultrasonic extraction equipment for their production requirements. Batch as well as continuous inline process setups are readily available and can be shipped off at the same day.

High Efficiency Extraction with Hielscher Ultrasonicators

Hielscher Ultrasonic extractors efficiently disrupt vegetable cells, increase the surface area of the plant material for solvent penetration, as well as improved mass transfer, which results in the quick and complete release of phytochemicals (secondary metabolites). Designed with regards to user-friendliness, Hielscher extractors are quickly installed and can be safe and intuitively operated.
 
The table below gives you an indication of the approximate processing capacity of our ultrasonicators: