Graduate Thesis Or Dissertation
 

Influence of cultivar and maturity on blackberry polyphenolics and investigation of sediment formation in blackberry juice

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  • The influence of cultivar and maturity on polyphenolic composition and antioxidant activity was investigated by UV-Visible spectrophotometry and analytical high performance liquid chromatography (HPLC) in commercially important blackberry cultivars and selections. The anthocyanin pigments changed tremendously with ripening. Total anthocyanins increased from 74.7-317 mg/100g fw from underripe to over ripe for 'Marion', and from 69.9-164 mg/100g fw for 'Evergreen'. Total phenolics did not show marked change with maturity with values slightly decreasing from underripe to ripe. Antioxidant activities, while increasing with ripening, did not show the noticeable change that total anthocyanins exhibited. The total phenolic and total anthocyanin contents varied greatly among 11 cultivars. Total anthocyanins ranged from 131-256 mg/100g fw (mean = 198), total phenolics from 682-1056 mg GAE/100g fw (mean = 900), ORAC from 37.6-75.5 μmolTE/g fw (mean = 50.2), and FRAP ranged from 63.5- 91.5 μmolTE/g fw (mean = 77.5). Four blackberry cultivars were found to be higher in total anthocyanins and total phenolics than 'Marion' and 'Evergreen', the predominant commercial cultivars in the Pacific Northwest. The results from these studies confirmed that blackberries are a good source of natural antioxidants and colorant, and demonstrated the potential for obtaining new cultivars with high pigment/phenolic content through classical plant breeding. The investigation on the incidence of haze and sediment formation revealed that the sediment in the commercial reconstituted 'Evergreen' blackberry (CRE) juice was composed of ellagic acid, protein, and unidentified compounds. The qualitative tannin and protein-tannin haze test indicated that the sediment was predominantly tannin or protein-tannin complexes. Nitrogen determination showed the sediment to be 6.69 ± 2.21% (w/w) protein on a dry weight basis. Almost all of the extractable material was identified as ellagic acid by HPLC and LC-MS. The ellagic acid content of the wet sediment was 0.05 g/100g while it was 7.41 g/100g in freeze-dried sediment. Tannase enzyme did not significantly decrease the concentration of ellagitannins in 'Marion' blackberry juice in this study.
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