Secondary metabolites, like phenolic acids and anthocyanins, offer plenty of health benefits, some of which are the result of their being antioxidants. However, several factors affect the volume of antioxidants a product like a botanical extract contains. One of these factors is the extraction method. 
An anthocyanin is a water-soluble bioactive compound that possesses a medium to high polarity. The therapeutic treatments and preventions made possible by anthocyanins can include vision problems, various microbial infections, diarrhea, hypertension, and liver dysfunction.
Red Grape Pomace
Red grape pomace (RGP) typically comes from creating grape juice or vinification (creating wine from grape juice), throughout which ripened red grapes are mechanically pressed and either fermented by pomace drying or direct exposure to drying following grape pressing.
The process chosen for extraction affects the sensory and nutritional characteristics of RGP. Additional parameters that affect the end product include selecting the right solvent, solvent/feed ratio, extraction time, particle shape and size, agitation speed, material uniformity, pressure, temperature, power, and equipment frequency.
However, researchers pose that the extraction time might be the most crucial parameter.  The longer it takes to extract an analyte from the biomass, the more the process costs and, hence, the more the product costs. Consequently, higher product costs tend to deter consumers from purchasing it, depriving them of the nutraceutical benefits of RGP.
Supercritical Carbon Dioxide Extraction
Supercritical carbon dioxide (SCCO2) extraction has proven to be a fast, eco-friendly, selective, and residue-free extraction process. The method has previously been used to extract essential oils from vegetation and for decaffeination, to name an ultra-limited few.
Extracting Anthocyanins from Grape Pomace Using Supercritical Carbon Dioxide
In a study by Pazir et al., researchers extracted RGP’s anthocyanins using SCCO2.  Throughout the experiment, researchers ensured a constant pressure of 100 bar and a temperature of 95°C.
Then, researchers measured the total monomeric anthocyanin content (TMAC) and total antioxidant capacity (TAC) values at the 30-, 60-, 90-, 120-, 150-, and 180-minute intervals. They found that the extractable TAC and TMAC values plateaued over time (highest efficiency was achieved after 30 minutes), while the cumulative antioxidant capacity and anthocyanin content rose over time.
SCCO2 extraction provides a more environmentally friendly approach compared to some traditional options such as using organic solvents. This study showed lower extraction yields compared to traditional extraction, however, the extraction time was shorter. Moreover, SCCO2 extraction is a cost-effective solution to the food industry’s challenges regarding extraction efficiency and the quality of the extracted bioactive compounds.
Reference Pazir F, Koçak E, Turan F, Ova G. Extraction of anthocyanins from grape pomace by using supercritical carbon dioxide. Journal of Food Processing and Preservation. 2020;45(8). doi:10.1111/jfpp.14950 [journal impact factor = 2.190; times cited = 2]
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