MATERIALS ANDMETHODS RESULTS

Antioxidant activity averaged over all extraction times and

solvent:waste ratios was significantly different (p<0.05) between

solvents, with 50% acetone demonstrating higher yield. (Table 1).

The 0.01% pectinase and petroleum ether solvents were

significantly less effective for extracting antioxidant compounds.

Therefore only the antioxidant activity of 50% acetone and 70%

methanol extracts will be presented (Fig. 5).

Influence of solvent extraction on antioxidant activity of Cynthiana grape

pomace using Oxygen Radical Absorbance Capacity (ORAC) assay

Ioannis P. Oikonomakos, Akhila Vasan, William McGlynn and Christina A. Mireles DeWitt

Robert M. Kerr Food & Agricultural Products Center, Oklahoma State University, Stillwater, OK, 74078

Industrial waste streams from horticultural processing may be a potential

source for dietary antioxidants. Our study focused on developing a rapid

and scalable method for screening winery waste for antioxidant activity

using different combinations of solvent extractions.

Our results showed that all extracts had antioxidant activity. Extraction

efficiency was significantly different (p<0.05) among all solvents. Higher

activity was observed in the 50% Acetone (27-37µmoles Trolox

equivalents/g pomace) and 70% Methanol extracts (17-24µmoles Trolox

equivalents/g pomace). The antioxidant activities of petroleum ether and

pectinase/water extracts were much lower, at 2 and 5µmoles Trolox

equivalents/g pomace respectively. For all solvents, 8h of extraction at 4:1

solvent to sample ratio showed the highest activity.

ABSTRACT

Fig. 1. Cynthiana (=‘Norton’)

Grape pomace from cultivar Cynthiana (Vitis aestivalis) (Fig.1)

Screening

Liquid N2

Grinding 4oC

Storage -20oC

Sample Preparation

Fig. 2. Extraction

Table 1. Average antioxidant activity of Cynthiana extracts.

Solvent

Average Activity

(µmoles TE/gr tissue)

50% Acetone 32a

70% Methanol 21b

0.01% Pectinase 5c

Petroleum Ether 2d

ACKOWLEDGEMENTS

For all solvent ratios and shaking times, the 50% acetone showed

significantly (p<0.05) higher antioxidant activity than the 70%

methanol extracts. Highest yields were obtained at 8h shaking and

4:1 solvent:waste, with ≈37µmoles TE/g tissue for the 50%

acetone and ≈24µmoles TE/g tissue for the 70% methanol (Fig. 5).

Fig. 4. Plate reader

Overall, our screening method allowed us to identify potentially high-value

grape processing waste products, thus paving the way toward developing a

commercially-viable method for extracting antioxidants from grape pomace.

• 50% acetone

• 70% methanol

• Water + 0.01% pectinase

• Petroleum ether

Solvent : Pomace

2:1 & 4:1

Extraction time (h)

1, 2, 4, 8Vacuum

Filtration

Solvent

Adjustment

Solvent

Treatment

Storage -20oC

Sample Extraction

Fig.3

ORAC Assay Fig. 4

Sample AnalysisFig. 3. Sample filtration

Fig. 2. Extraction

Fig. 2

Results were expressed as

Equivalent µmoles of Trolox per

gram tissue (TE/g tissue).

CONCLUSIONS

• Our study indicates that Cynthiana grape pomace has a significant

amount of antioxidants (Table 2), and could be extracted as part of an

industrial waste utilization system.

• 50% acetone is an effective solvent to extract these antioxidants with

satisfactory yields even at lower solvent:pomace ratio and extraction

times, suggesting that the majority of the solvent’s extraction potential

can be achieved using half the volume and time of the maximum yield.

This may prove to be more economical for screening studies.

Petroleum Ether 2

a Numbers with different letters denote significance at p<0.05

Activity shown is an average across all shaking levels and ratios of solvent

Fig. 5. Average antioxidant activity of 50% acetone and 70% methanol extracts

Table 2. Antioxidant activity from different food sources

Food Source/products

Total ORAC

(μmoles TE/ 100 gr tissue)

Blackberries, raw 5347

Blueberries, raw 6552

Grapes, red, raw 1260

Grapes, white or green, raw 1118

Grape juice, white 793

Grape juice, red 1788

Tomatoes, raw and cooked 367-694

Cynthiana pomace ≈2000-4000

Values obtained from USDA 'ORAC of selected foods - 2007'

• Future research will be

focused on identifying the

antioxidant compounds in

grape pomace and

screening for antioxidants

at different steps of wine

production.Oklahoma State University

Agricultural Experiment Station

Robert M. Kerr

Food and Agricultural Product Center

Oklahoma State University

Department of

Horticulture & Landscape Architecture