Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Food, Nutrition and Packaging Sciences

Advisor

Chen, Feng

Committee Member

Coffee , Aubrey

Committee Member

Northcutt , Julie

Abstract

Vitis rotundifolia also called 'Muscadine' grows abundantly throughout the southeastern United States. Muscadine grapes have desirable flavors, making them suitable to be either consumed as fresh fruit or made into wine and jam. Moreover, muscadine grapes have been reported containing rich complex phytochemicals, including anthocyanins and polyphenols that possess antioxidant, anti-cancer, anti-inflammatory and antimicrobial activities. Therefore, muscadine grapes have become increasingly popular in recent years due to its unique aroma, as well as health benefits. Various volatile compounds contribute to the aromatic flavors of muscadine grapes. In regards of their low concentrations, conventional simultaneous distillation and extraction (SDE) and solid phase microextraction (SPME) were applied to extract and concentrate volatile components. Two different varieties, i.e., the Carlos and Noble muscadine grapes, were used because they are the most promising bronze and black muscadine cultivars for commercial wine production. Three major aromas of the Carlos grapes were identified by SDE-GC-MS, which are listed below in the order of their concentrations from high to low: hexanal, 2-hexenal and1-hexanol. In comparison, the volatile compound with the highest concentration in the Noble was 2-hexenal, followed by hexanal and &alpha-terpineol. The Carlos and Noble grapes shared a majority of the same volatile compounds with few additional differing volatiles. Butyl acetate, 1-hexanol and nonanal had higher concentration in the Carlos than in Noble grapes whereas Noble contained higher amounts of 1-octanol and &alpha-terpineol than Carlos grapes using SDE. Using SPME-GC-MS, the detected volatiles with the highest concentration was ethyl acetate, followed by &beta-damascenone and ethanol in the Carlos, while the principle volatile compounds of the Noble extract were ethyl acetate, (Z)-4-decen-1-ol and &alpha-terpineol. The concentrations of some volatile compounds were different between the two varieties. Linalool, &alpha-terpinolene and &alpha-terpineol had higher concentrations in the Noble than in Carlos grapes, but Carlos contained higher amount of ocimenol and 1-hexanol than Noble grapes. SDE could extract relatively high concentrations of C6 compounds (hexanal, 2-hexenal and 1-hexanol) but SPME fiber adsorbed high amount of esters (ethyl acetate) from both grape varieties. Both SDE and SPME were reliable for extraction and identification of major volatiles from muscadine grapes. However, furfural and 2-pentylfuran (artifacts of the Maillard reaction) were only detected by SDE-GC. Additionally, SPME showed low levels of baseline noise which facilitates the identification of greater number volatile compounds using GC-MS. In summary, SPME is a solvent free alternative extraction technique for extraction of volatile compounds.

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