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Access Type

WSU Access

Date of Award

January 2012

Degree Type

Thesis

Degree Name

M.S.

Department

Nutrition and Food Science

First Advisor

Kequan Zhou

Abstract

The health benefits of antioxidants have been supported for decades. Dietary acquisition of these compounds is common and berries are especially rich in antioxidants. Due to the roles they play in protecting the human body from oxidative odamage, studies of the bioaccessibility of antioxidant absorption are on the rise. In this study, the stability of antioxidant capacity via in vitro digestion of gooseberries was investigated. Digested and undigested samples of two species of gooseberry, Tixia (T, bright red) and Invicta (I, pale green), were tested for antioxidant capacity via total phenolic content (TPC) assay, DPPH radical scavenging assay, and oxygen radical absorbance capacity (ORAC) assay. Results from this study implied that digestion enhances the availability of antioxidants in these fruits, where the digested batches showed a higher antioxidant content and ability, with p<0.01 (T & I), p<0.05 (T & I) and p<0.05 (I only) as computed from TPC, DPPH and ORAC, respectively. Another remarkable finding noted that Tixia species possess higher antioxidant ability than Invicta species, according to TPC, DPPH, and ORAC with p<0.001, p<0.001 and p<0.01, respectively. In addition to determining the total antioxidant content and capacity through the aforementioned assays, high performance liquid chromatography (HPLC) profiling enabled us to identify 8 of the antioxidants found in Tixia and Invicta, using 23 standard antioxidants as reference. The profiling revealed that only quercetin hydrate was significantly higher in digested samples (p<0.05). It is important to note that digestion may also modify the chemical characteristics of antioxidants thus altering their identification but not necessarily their function. In conclusion, antioxidants of gooseberry (Tixia and Invicta) may have an enhanced bioaccessibility after in vitro digestion but compounds contributing to the antioxidant capacity of these fruits require further investigation.