44C-19 |
Analysis of raisin extracts to determine phenolic content and antimicrobial activity |
J. G. LOAIZA1, E. A. Murano2, and L. Cisneros-Zevallos1. (1) Horticulture, Texas A&M University, Texas A&M University, Horticulture & Forest Science Bldg. # 202, College Station, TX 77843, (2) Animal Science, Texas A&M University, Texas A&M University, Kleberg Center, College Station, TX 77843 Phenolic compounds are becoming of interest as researchers are discovering functional activities as drugs, colorants, flavors, and antioxidants. Some phenolics share some biological and chemical properties that might be effective inhibitors of chemical mutagens and/or carcinogenesis. Previous studies have shown that naturally occurring hydroxycinnamate derivatives have antimicrobial activity. Phenolic content is also closely associated with the sensory and nutritional quality of fresh and processed plant foods. Experiments were conducted to determine the type and amount of phenolics present in raisins and test their extracts to identify possible antimicrobial activity. Total phenolic content, anthocyanins, and antioxidant activity were assayed spectrophotometrically using standardized methods reported in the literature. HPLC was used to separate, identify and quantify the phenolic content. A spectrophotometric test and the Kirby-Bauer Method were used to study the effect of raisins extracts on microbial growth. Raisins seem to have a considerable content of phenolic compounds. Golden raisins showed the highest concentrations, which can be due to the prevention of browning by SO2 application. Anthocyanins were not detected in any of the raisins analyzed. Golden raisins also showed three times higher antioxidant activity than Thompson-seedless and Zante raisins. Tentative identification of the phenolic profile by HPLC suggests the presence of quinic and gallic acid, chlorogenic and caffeic acids, catechin, epicatechin, and others yet to be identified. Water and methanol extracts from raisins greatly inhibited the growth of L. monocytogenes and E. coli 0157:H7 in the ranges of 70-95% and 50-70% respectively. This results where comparative to a control and 2% chlorogenic acid solution. Our results suggest that raisins have antimicrobial properties that are related to their phenolic content. Even though much of the phenolics is lost because of browning reactions, the drying process when making raisins concentrates the remaining amounts and make them significant on per weight basis.
Session 44C, Fruit & Vegetable Products: Chemistry
|