Location: Arkansas Children's Nutrition CenterTitle: Release of bound procyanidins from cranberry pomace by alkaline hydrolysis) Author
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2010
Publication Date: 7/14/2010
Citation: White, B., Howard, L.A., Prior, R.L. 2010. Release of bound procyanidins from cranberry pomace by alkaline hydrolysis. Journal of Agricultural and Food Chemistry. 58(13):7572-7579. Interpretive Summary: Cranberry juice has long been recognized for its ability to prevent urinary tract infections, but there are also several other health benefits associated with consumption of cranberries. Cranberry pomace is composed primarily of seeds, skins, and stems, which are leftover from the industrial juicing and canning processes. Procyanidins are phytochemicals in cranberries that have beneficial anti-oxidant properties. We developed a new method to extract procyanidins from dried cranberry pomace. When compared to previously published and conventional extraction processes, our method increased procyanidin extraction by 3.8 to 14.9-fold. This new method is highly recommended for maximal extraction of these cranberry phytochemicals.
Technical Abstract: Procyanidins in plant products are present as extractable or unextractable/bound forms. We optimized alkaline hydrolysis conditions to liberate bound procyanidins from dried cranberry pomace. Five mL of sodium hydroxide (2, 4, or 6N) was added to 0.5 g of cranberry pomace in screw top glass tubes, and the tubes were flushed with nitrogen. The tubes were then placed into a water bath set at 25, 40, or 60 °C with shaking for varying amounts of time, which depended on the temperature. Sodium hydroxide was then neutralized to pH 6 – 7 with concentrated HCl. Procyanidins were extracted with ethyl acetate and analyzed using normal phase high performance liquid chromatography (HPLC). Alkaline hydrolysis resulted in an increase in procyanidin extraction, and greater amounts were extracted at higher temperature, short time combinations. The most procyanidins (DP1 – DP3) were extracted at 60 °C for 15 m with each concentration of NaOH extracted. When compared to conventional extraction using homogenization with solvent, treatment with NaOH increased procyanidin oligomer extraction by 3.8 to 14.9-fold, with the greatest increase being DP1 (14.9x) and DP2 (11.4x) procyanidins. Treatment of the residue remaining after conventional extraction with NaOH also resulted in increased procyanidin extraction, indicating that procyanidins are not fully extracted under conventional extraction procedures.