Location: Healthy Processed Foods Research
2013 Annual Report
(2) Establish the localized and distal effects of UV-B treatment on plant tissues (e.g. skin vs. interior).
(3) Determine the effect of postharvest conditions on the synthesis of phenolic compounds with and without UV-B treatment and analyze the stability of these compounds during normal storage. Determine the effects of these treatments on sensory quality and nutritional value.
(4) Verify enhanced bioavailability of phenolic compounds following UV-B treatment using in-vitro and in-vivo methods.
1)the synergistic response resulting from the combination of wounding and UV-B treatment,.
2)the influence of genotype on responsiveness, and.
3)processing conditions that yielded maximal enhancement of antioxidant activity without reducing product quality. Research efforts consisted of nearly 900 samples, including whole and precut root crops and vegetables evaluated under multiple conditions, and confirmed that among the crops tested, carrot is the most responsive to UV-B treatment. Samples of whole sweet potatoes, colored potatoes, and white sweet corn, and sliced sweet potatoes, radish and daikon did not show a measurable response to UV-B treatment.
We evaluated five commercial pre-cut carrot products possessing increasingly greater area/weight ratios and found that UV-B responsiveness, as measured in terms of TSP, AC, chlorogenic acid content, and PAL activity, increased directly as the area/weight ratio increased. We also found that UV-B light exposure only slightly increased the surface temperature of the carrot samples and did not stimulate the accumulation of carotenoids.
Analysis of the 21 varieties UV treated carrots revealed that response and the level of responsiveness was dependent upon the color of the carrot, suggesting that genotype and phenotype plays a role in determining responsiveness.
The effect of post-UV treatment conditions and cold storage on the synthesis and stability of phenolic compounds in carrots with and without UV-B treatment was examined. We found that increases in the TSP content of UV treated carrot products were dose and temperature dependent. We were able to identify optimal treatment, handling, and packaging conditions that produced a 2-fold increase in AC in baby carrots while maintaining product quality that was shelf-stable for 21 days. Bench sensory tests indicated that there were no differences in flavor, odor, appearance and texture between UV-treated and control baby carrots.
Tissue culture studies are currently underway to investigate bioavailability of antioxidants produced by UV treatment.
Our research topic and results have generated considerable interest in the project among large-scale agricultural producers, independent farmers, carrot breeders, extension specialist (UC Davis), and scientists around the world. Individuals and organizations have approached us with samples of the speciality crops they produce asking that samples be tested for their UV-B responsiveness. Several collaborations were established for the joint investigation of the responsiveness of several different specialty crops to UV-B irradiation.