36E-85 |
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B. ZHAO and C. A. Hall, III. Dept. of Cereal and Food Sciences, North Dakota State Univ., Harris Hall 223, Fargo, ND 58105 Raisins are ranked among the highest concentration in the total phenolics content and highest levels of total antioxidant activity in solid fruit products. The positive correlation of the antioxidant activity and phenolics content were also confirmed. Hydroxymethylfurfural (HMF) is often used as an index of total browning reaction products in food which also have antioxidant activity. Sample extraction procedures are often regarded as bottlenecks in analytical methods. We hypothesize that the phenolics and Browning reaction products content and antioxidant activity of raisin extracts is closely dependent on the ratio of solvent and water. Our objective is to optimize the solvent concentration on the content of phenolics and HMF in the raisin extracts and its antioxidant activity. Ground raisins were extracted with methanol at different concentration (0% to 100%). The slurry was homogenized and extracted under ultrasound for 20 min. Suspensions were centrifuged at 4000 rpm for 15 min. The sample pellets were reprocessed two times. Phenolic and HMF content of raisin extracts were determined using the spectrophotometric analysis with Folin-Ciocalteu's phenol reagent and HPLC methods. Antioxidant activity was evaluated by oil stability index (AOCS official method). Our results showed that, the HMF content raisin extract was higher at 100% methanol concentration, but the phenolics content and antioxidant activity was higher at 60% and 80% methanol concentration. These results suggest that methanol concentration has significant influence on the content and antioxidant activity of the raisin extract. Understanding the extraction conditions and antioxidant activity of raisin extract can expand raisin utilization and marketability.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |