Optimization and metabolomic characterization of a green extraction protocol for wine grape polyphenols

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In Niagara region, some harvesting of wine grapes occurs between November and February for Ice Wine and Ice Syrup production. At this time of year, grapes have accumulated high levels of polyphenols, which are molecules like resveratrol and quercetin that have been linked to positive health outcomes when included in the diet or as nutraceutical supplements. Polyphenols accumulate in the skins and seeds of grapes, which are waste byproducts of Ice Wine and Ice Syrup production. Presently, these parts of the grapes are being discarded and no value is realized from their rich polyphenol content. Recently, we developed a 'green' extraction protocol to isolate polyphenols from winter-harvest grapes and validated the approach by measuring the levels of 28 different polyphenolic molecules. To create a potentially edible product that could be provided as a tablet, we used beta-cyclodextrin as a carrier molecule for polyphenols in water. Polyphenols have very low water solubility but are readily loaded into beta-cyclodextrin which increases their solubility in water by several thousand-fold. We now wish to develop this approach into a commercial scale that can be used to process many tonnes of skin/seed waste from winter-harvest grapes. This application details the approach we will use. In collaboration with Sweet & Sticky and NSF International, we will refine the extraction process by testing several pre-processing and processing steps to identify those that are efficacious and cost effective, and could therefore be implemented commercially. We will then test several post-processing strategies to determine one that maintains the stability of polyphenols in the product. Polyphenols can degrade over time, particularly if exposed to heat and light. We believe that their loading into beta-cyclodextrin will protect against this possibility, but need to demonstrate this. We will use metabolomic profiling (i.e. measurements of a wide range of polyphenolic molecules), performed at the Cold Climate Oenology and Viticulture Institute at Brock University, to assess the yield and stability of polyphenols under all tested conditions. The proposed studies will enable Sweet & Sticky to develop an industrial protocol that can be used commercially immediately.