36E-39 |
|
J. LEE and S. T. Talcott. Dept. of Food Science and Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370 Alpha-glucosidase (E.C. 3.2.1.21) and tannin acyl hydrolase (EC, 3.1.1.20) are commonly used as a processing aid for foods and beverages and is often associated with quality improvement such as releasing aroma components or removing undesirable compounds. However, there is no published data for the activity of these enzymes on ellagitannins and ellagic acid glycosides in food systems. By exploring the characteristics of these ellagic acid precursors in the presence of each enzyme, the functional properties of these compounds can be evaluated in the absence of a heat catalyzed hydrolytic reaction. Polyphenolic isolates from muscadine grape juice were prepared using Sep Pack C18 cartridges and non-retained and ethyl acetate-soluble fractions collected that contained primarily ellagitannins and ellagic acid glycosides, respectively. Alpha-glucosidase (1.33 units/ml) and tannase (1.74 units/ml) was solubilized in 0.2M phosphate buffer at pH 5 and added into each fraction and held at 37 o C for 3 hrs. Reactions were stopped in boiling water for 1 minute. Enzyme treated samples were analyzed compared to controls with no added enzymes. Controls were prepared at pH 3 and 5 in order to determine the influence of pH on enzyme reaction and the evolution of free ellagic acid. Alpha-glucosidase showed higher reactivity to ellagic acid xyloside (3.14 to 1.05 mg/kg) compared to rhamnoside moieties when monitored by HPLC, whereas the rhamnoside was unaffected by the enzyme. Incubation with tannase revealed no specific activity for the ellagic acid glycosides or hexahydroxydiphenoyl units of ellagitannins was detected. However, free gallic acid significantly increased in the presence of tannase (17.8-fold increase) indicating the presence of gallotannins or gallic acid esterified to ellagitannins. Alpha-glucosidase demonstrated a potential application for products containing ellagic acid glycosides whereas tannase had little effect on ellagic acid precursors.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |