Date of Graduation

5-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Food Science (PhD)

Degree Level

Graduate

Department

Food Science

Advisor

Luke R. Howard

Committee Member

Ya Jane Wang

Second Committee Member

Ron Buescher

Third Committee Member

Ronald L. Prior

Fourth Committee Member

Edward E. Gbur

Keywords

Biological sciences; Anthocyanin; Cranberry juice; Cranberry pomace; Flavonoids; Polyphenolics; Procyandin

Abstract

Historically, cranberry juice has been consumed to prevent urinary tract infections. These and other health benefits, including reduced risks of cancer and cardiovascular disease, are believed to be due to the presence of polyphenolics, specifically flavonoids. Cranberry pomace is the by-product of cranberry processing which consists of seeds and skins. This research focuses primarily on the effects of processing on the flavonoid composition of cranberries and cranberry pomace. First, the concentration of flavonoids during juice processing was evaluated. It was determined that anthocyanins were degraded readily compared to other flavonoids, and a significant amount of flavonoids were retained in the pomace. Additionally, hydrolysis of flavonol glycosides to aglycones occurred due to heat treatment. Next, dried cranberry pomace from industry was characterized based on its proximate and polyphenolic content. The pomace consisted primarily of insoluble dietary fiber and had high concentration of anthocyanins (111.5 mg/100 g DW), flavonols (358.4 mg/100 g DW), and procyanidins of DP 1-6 (167.3 mg/100 g DW). Next, extrusion processing was used to alter the flavonoid composition of cranberry pomace. Extrusion processing increased the amounts of DP1 and DP2 procyanidins and decreased the amounts of procyanidins with DP>4. Total flavonols and antioxidant capacity also increased after extrusion. Alkaline hydrolysis was also used to extract procyanidins from cranberry pomace and alter their composition. When compared to conventional extraction, alkaline hydrolysis increased procyanidin oligomer extraction with the greatest increase being DP1 (14.9x) and A-type DP2 (8.4x) procyanidins. Treatment of the residue remaining after conventional extraction using alkaline hydrolysis resulted in further procyanidin extraction, indicating that procyanidins are not fully extracted by conventional methods. This was confirmed by staining samples of cranberry pomace and residues remaining after conventional extraction and alkaline hydrolysis with dimethylaminocinnamaldehyde to visualize procyanidins. Alkaline hydrolysis was also used on other fruit processing by-products, and it was revealed that these by-products also contained bound procyanidins. This research indicates that cranberry pomace is a rich source of polyphenolics, which could be extracted for nutraceutical purposes. Additionally, the composition of procyanidins in the pomace could be altered by extrusion or alkaline hydrolysis to increase their bioavailability and health-promoting properties.

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