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Bioactive and functional properties of phenolic compounds from new sources of edible plant tissues
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New sources of crops high in phenolic compounds were analyzed for their antioxidant activity, antimicrobial capacity, and color potential. These crops were native Andean red sweetpotato and purple corn, and new peach, plum and purple carrot varieties from breeding programs. For antioxidant activity, DPPH (2,2-diphenyl-1-picrylhydrazyl) was used as the free radical source and results were expressed on Trolox (6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid) basis. Purple corn had 2 to 6 times higher antioxidant activity than blueberries analyzed. Red sweetpotato had higher activity than one blueberry and similar as two others. Plum BY94M1945 had higher antioxidant activity than one blueberry while peach BY94P7552 and purple carrot had similar activities. Crops were analyzed by sections, with the epidermis and exocarp having the greatest concentrations of anthocyanins, phenolics and antioxidant activity. Cob epidermis had 6.6 times higher antioxidant activity than whole corn. Positive correlations were obtained between anthocyanins and phenolics vs. antioxidant activity. Antimicrobial activity of purple corn, red sweetpotato, plum and purple carrot was assayed on Escherichia coli O157:H7 and S. Enteritidis, and correlated with antioxidant activity, anthocyanin and phenolic content of the extracts. Three antimicrobial assays showed different inhibitory results. Plum extracts showed bacterial inhibition on the three assays and highest inhibition against both bacteria as measured with the plate count assay. Purple carrot and red sweetpotato showed some effect against S. Enteritidis but none against E. coli. Purple corn showed no effect against either bacterium. Correlations between bacterial growth inhibition and phenolic content (excluding anthocyanins) were significant. For colorant stability aqueous red sweetpotato and purple corn extracts were evaluated at different pH, temperature, light and oxygen conditions, compared to commercial purple carrot, red grape and synthetic colorants. pH was found to be the governing factor for degradation at all conditions tested, followed by temperature, then light. Exposure of extracts to air caused no degradation. Acylated red sweetpotato and commercial purple carrot colorants showed higher stability than non-acylated purple corn and commercial red grape. Commercial red grape colorant showed the least stability to the tested conditions. Parameters measured included browning index, polymeric color, color retention and spectral absorbances.
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Includes bibliographical references (leaves 126-136).
Issued also on microfiche from Lange Micrographics.
Cevallos, Bolivar Alejandro (2001). Bioactive and functional properties of phenolic compounds from new sources of edible plant tissues. Master's thesis, Texas A&M University. Available electronically from
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