Date of Completion

5-11-2013

Embargo Period

5-21-2013

Advisors

Mark Brand; Ock Chun

Field of Study

Nutritional Science

Degree

Master of Science

Open Access

Open Access

Abstract

Chokeberry (Aronia melanocarpa, Aronia prunifolia, Aronia arbutifolia) is notable for its high phytochemical content, particularly anthocyanins and proanthocyanidins. Aronia berries of different genotypes may vary in their polyphenol content, so it is important to characterize these compounds based on species, and to determine whether or not aronia fruit color correlates with phytochemical content. Using normal-phase HPLC, UPLC-MS, and the DMAC and Folin-Ciocalteu assays, polyphenols in twelve different aronia accessions were quantified and characterized based on fruit color. Significant diversity was observed in anthocyanin content among berries of different colors, with black aronia berries (mean = 10.47 mg/g DW) having universally higher levels of anthocyanins than purple aronia berries (mean = 3.24 mg/g DW), and lastly aronia berries (mean = 0.63 mg/g DW) (P = 0.0018). Total phenol values were, however, were higher in red and purple chokeberries than black chokeberries (mean total phenol values were 185, 187, and 167 mg GAE/g DW, respectively). Proanthocyanidin, hydroxycinnamic acid, and flavonol contents did not differ among the three aronia species. Differences in moisture percentage among different accessions did not significantly affect polyphenol content.

Due to the potential of chokeberry as a nutraceutical crop or a source of polyphenols for supplements, we determined the changes in polyphenol content and antioxidant activity of the ‘Viking’ chokeberries (the most readily available commercial variety), throughout fruit ripening. ‘Viking’ chokeberries were harvested once per week for 7 weeks, juiced, and their polyphenol content was quantified using UPLC-MS, and the DMAC and Folin-Ciocalteu assays. Changes in sugar content were analyzed using a refractometer and quantified in degrees brix. Antioxidant activity was analyzed using the FRAP assay. Anthocyanins increased by 227% between the first and fifth weeks of ripeness, then declined (P < 0.0001). Proanthocyanidins increased by 67% through ripening (P < 0.0001), sugar content increased 36% (P < 0.0001) between the first and last week of harvest, and hydroxycinnamic acids decreased by 33% (P < 0.0001). Total phenols increased by 24% (P < 0.0001) and antioxidant activity via the FRAP assay increased by 53% (P < 0.0003) during ripening in ‘Viking’ chokeberries. No significant trend was observed in flavonol content throughout the growing season. In conclusion, antioxidant capacity correlates most closely with total phenol content, and week 7 is the optimal time to harvest aronia berries with respect to antioxidant capacity.

Major Advisor

Bradley Bolling

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