SUBCRITICAL WATER EXTRACTION OF ANTHOCYANINS FROM FRUIT BERRY SUBSTRATES

摘要

The extraction of anthocyanin-based pigments from fruit berries and grapes is normally accomplished using ethanol or aqueous-based ethanol solutions, and occasionally ethyl acetate, acetone, or methylene chloride. Although ethanol is classified as a GRAS (Qenerally-Recognized-As-Safe) solvent, its utilization must be strictly accounted for under legal statues. Subcritical water under modest compression above the boiling point of normal water is an alternative medium to ethanol due to its temperature-dependent dielectric constant and cohesional energy density. In this study, Subcritical water under pressure, and held at temperatures between 110-160℃ was utilized for the extraction of anthocyanin-based pigments from fruit berries (both wet and dry), such as elderberry, raspberry, bilberry, chokeberry; and their associated stems, skins, and pomaces. Extraction and screening experiments were executed using a home-built, flow through extraction system in which water and acidified water solutions were fed at a high velocity with the aid of liquid booster pump in an attached Spe-ed unit module. Additional screening experiments were conducted utilizing a Dionex Model 300 ASE (Accelerated Solvent Extraction) instrument in which the default values for normal operation of the ASE were changed via the microprocessor controller to facilitate extractions under the above conditions. Samples of various fruit berries and their by-products (pomaces) were placed in the extraction cell and the oven heated to temperatures between I20-160℃. Both deionized and Milli-Q-purified neat water as well as acidified water (0.01% HCl, pH ～ 2.3) were fed typically at a rate of 24 mL/min against a constant pressure of 40 bar (580 psi). Similarly, rapid extractions were conducted on the ASE system using both pure water, water-ethanol mixtures, and acidified water. Extractions were monitored visually, spectrophotometrically, and via HPLC analysis. The efficiency of the sub-H_2O extractions were compared to results obtained using a 70% ethanolic extract.