Antioxidant properties of three local onion (Allium cepa, Allium ampeloprasum, Allium ascalonicum) varieties

Date

2011

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nieva T. Librojo-Basilio

Committee Member

Desiree Belina-Aldemita

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Abstract

A comparison of the antioxidant properties of three local onion varieties (Allium cepa, Allium ampeloprasum, and Allium ascalonicum) and that of a commercially available onion powder was done. Antioxidant properties in terms of ability to reduce Fe3+ ions (reducing power) and to scavenge DPPH radicals (radical scavenging capacity) were carried out. The presence of phenolic compounds, which are deemed responsible for antioxidant activities, was determined. The shallot variety was found to have shown the have the highest reducing power (RP)at 46.8% and the highest DPPH scavenging capacity (SC) of 51.05% after 60 minute incubation time while the white variety has the lowest values of 12.6% and 27.14%, for RP and SC, respectively. Determination of antioxidant contents showed that the shallot variety was found to have the highest values for total phenolics (TPC), total flavonoids (TFC), and total anthocyanin content (TAC) with values of 182 mg gallic acid equivalents (GAE) / g fresh weight (FW), 32.41 mg quercetin equivalents (QE) / g FW, and 3.34 mg anthocyanin / g FW, respectively. On the other hand, the white variety has the lowest amounts of antioxidants with values of 100 mg GAE / g FW, 9.791 mg QE / g FW, and 0.465 mg / g FW, for TPC, TFC, and TAC, respectively. The commercial onion powder was found to have lower values than the fresh samples, showing that the antioxidant activities and active compounds of theonion were not retained during processing to powder form for commercial use. Using Pearson’s correlation method, it was found that SC was perfectly correlated with TPC and highly correlated with TFC and TAC. In contrast, the RP has low correlation with TPC but slightly correlated with TFC and TAC. The findings indicated that there are varietal differences in antioxidant properties of onions, with the colored varieties having higher antioxidant characteristics. Further, most of these properties were not retained in the preparation of commercial onion powder.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Document Type

Thesis

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