Undergraduate Thesis Or Project
 

Development of a colorimetric test kit to determine enzymatically produced pyruvic acid in sweet onions

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https://ir.library.oregonstate.edu/concern/undergraduate_thesis_or_projects/f7623f34v

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  • Sweet onions are valued for their unique flavor and praised for their health and dietary character. Onion sweetness is perceived as the degree of pungency decreases. Pungency can be quantitatively determined in onions by measuring enzymatically produced pyruvic acid. The onion industry quantifies a sweet onion as one having a pyruvic acid concentration of 1 – 4 μmol/g. Identification of pyruvic acid is accomplished by reacting onion extract with 2, 4-dinitrophenylhydrazine (DNPH) to produce a colored adduct that is measured spectrophotometrically. Currently, onion processors outsource pungency analysis to a laboratory in Texas. The cost and turn around time are both high. Satisfying the need for a modified method, where samples can be analyzed quickly on site, is the goal of this research. The laboratory method produced data qualifying sweet onions. Averages of 15 samples resulted in 4.05 ± 0.48 with a percent recovery by over-spiked samples of 104% ± 10.4%. Check standards reveal a percent recovery of 98% ± 0.78%. This method is reproducible and adaptable for a quick, field test kit for onion breeders. The test kit identifies pyruvic acid with the use of the DNPH color indicator, and qualifies sweet onions by comparing samples to a provided color chart. The test kit proposed reduces the cost of sweet onion analysis significantly and decreases the overall turn around time for pungency analysis.
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file details Thesis Presentation.ppt 07/26/2017 Public
file details Merrill, D. Thesis.pdf 07/26/2017 Public