36E-54

B. B. SURJADINATA and L. Cisneros-Zevallos. Dept. of Horticultural Sciences, Texas A&M Univ., 202 Horticulture & Forestry Science Bldg., 2133 TAMU, College Station, TX 77843-2133

In previous work, we found that the phenolic content and antioxidant capacity (AOX) in carrot tissue increased with wounding intensity (A/W). It has also been reported that UV-radiation may trigger the phenylpropanoid metabolism in plant tissues. Thus, by selective combination of stresses it may be possible to enhance the content of health promoting antioxidant compounds in plant tissues. The objective of this study was to determine the combined effect of wounding intensity (A/W) and UV-radiation on phenolic compounds, AOX, and the phenylalanine ammonia lyase (PAL) activity of fresh-cut carrots. Carrots were cut into slices, pies, and shreds (A/W of 4.2, 6.0, and 23.5 cm²/g, respectively) and irradiated with UV-A (90W), UV-B (90W) or UV-C (60W) for different exposure times. Afterwards, carrots were stored for 4 d in 4-L glass jars at 15^o C with periodic ventilation. Non-irradiated whole and wounded carrots were used as controls. Total phenolics, AOX, and PAL activity were quantified spectrophotometrically. Individual phenolics were separated by HPLC. Results indicated that phenolic content, AOX, and PAL activity increased in cut carrots with UV-C exposure time. Carrot pies showed a higher increase compared to the other cuts. Phenolics, AOX, and PAL activity were also increased when cut carrots were exposed to both UV-A and UV-B radiation. UV-radiation type affected the phenolic profile synthesis. Chlorogenic acid was induced by all UV radiations, while ferulic acid was induced only by UV-A and UV-B. On the other hand, isocoumarin was induced only by UV-B and UV-C. Other phenolics, such as p-hydrobenzoic acid, were not affected by UV radiation. In general, total phenolics were highly correlated with AOX for all treatments (R²>0.9). Combining abiotic stresses may selectively induce different phenolic profiles. These stresses could be used by the fresh-cut produce and food processing industries as tools to tailor the synthesis of desired phenolic compounds.

Session 36E, Fruit & Vegetable Products: General
8:30 AM - 12:00 PM, Monday AM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana