The development and optimization of membrane processes for separation and purification of bioactive phytonutrients from grapes and blueberries

Membrane processes for purification and concentration of bioactive phenolics products from grapes and blueberries, which include ultrafiltration, nanofiltration, diafiltration and reverse osmosis, have been developed and optimized.; Total phenolics, anthocyanins, sugars and individual compounds in the grapes and blueberries have been quantified by UV-vis spectrophotometry and HPLC. Experimental results have demonstrated that grapes and blueberries are a rich source of antioxidants. The effects of ethanol content and temperature on the extraction efficiency of phenolics from grapes were determined. The extraction study showed that 40--80 vol.% ethanol content showed higher extraction efficiency than at other levels, and anthocyanins experienced a rapid degradation loss when the extraction temperature was above 60°C. The molecular weights of polyphenoloxidase co-extracted in the grape extract are 30,000 Da and 52,000 Da.; The laboratory-scale membrane tests were conducted in a stirred cell. Concentration polarization was found as the dominant factor controlling the overall mass transport process. The bench-scale ultrafiltration, nanofiltration and reverse osmosis experiments were conducted in two cross-flow membrane systems. The effects of transmembrane pressure and feed concentration on membrane performance were determined. PM10 hollow fiber ultrafiltration membrane (MWCO = 10,000) showed good performance to process grape and blueberry extracts. GE nanofiltration membrane showed better selectivity than other tested nanofiltration membranes (i.e. DK, NF45 and GH). Experimental results also showed that SG reverse osmosis membrane could be used to concentrate phenolics products before spray drying. Membrane cleaning strategies were also developed for potential membrane fouling.; A membrane process was designed to concentrate and purify the phenolics product using the bench-scale experimental data. Through the process, the volume of the phenolics product was concentrated from 100 gpm to 9.5 gpm and the concentration of phenolics was increased from 16.7% (dry basis) to 94.1% (dry basis). A preliminary economic analysis gave a cost of {dollar}0.245 per pound phenolics product at an annual production capacity of 974,574 lbm.; Experiments of membrane fractionation of procyanidins extracted from grape seeds by pressurized liquid water were also conducted. These studies showed that procyanidins in the grape seed extract could be fractionated through a series of membrane processes. A concentrated product rich in oligomeric procyanidins was produced through the process.