Food Science and Technology Department


Date of this Version

Summer 8-2011


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Food Science & Technology, Under the Supervision of Professor Durward A. Smith. Lincoln, Nebraska: August, 2011

Copyright 2011 Julien Khalil


Grapes are an important source of bioactive compounds such as gallic acid, resveratrol, and catechin. The consumption of grapes is associated with a lower risk of diseases such as cardiovascular diseases and some types of cancer. Grape pomace and skins are good sources of many phytochemicals known for their antioxidant potential.

In this research, the peel of the Chilean “Flame” grape cultivar and the pomace of St. Croix, Frontenac and St. Pepin grape cultivars were subjected to a pulsed electric field (5 KV, 1 μFarad, 20 Pulses) and to an enzymatic treatment (Pectinase, 5KU). The total phenolic content, determined in gallic acid equivalents using the Folin-Ciocalteau assay was analyzed. In addition to that, some of the individual phenolics present in the extracts were identified and quantified using HPLC. Finally, the antioxidant potential of the extracts was calculated using the FRAP assay.

This research explored the possibility of establishing if by-products generated by wineries could become a potential source of polyphenols. Pulsed electric field and pectinase treatments were both effective in enhancing the extraction of polyphenols from grape pomace and peel. The extracts showed a strong antioxidant power.

Adviser: Durward A. Smith