Value-added product development utilizing Washington State grape seed flour

Clifford Hoye

The production of grape seed flour (GSF) from grape pomace, a waste product generated during winemaking, has been explored for use in product development due to its potential health benefits. However, research on the stability of GSF during processing and heating is limited. The overall objective of this study was to assess changes in phenolic content and antioxidant activity of GSF used as an ingredient in bread making. To determine the impact of heating time and temperature on the antioxidant activity of GSF, Merlot GSF from two harvest years (2007 and 2008) was heated at five different temperatures (120 to 240°C) for 0 to 90 mins. Total phenolic content (TPC), total flavan content (TFC), Trolox equivalent antioxidant capacity (TEAC), 2,2 diphenyl-1- picrylhydrazyl (DPPH) radical scavenging, and ferric ion reducing antioxidant power (FRAP) of the extracts were determined. Thermal treatment of Merlot GSF caused significant decreases in the TPC and antioxidant activity when heated ≥180°C. A strong correlation between antioxidant properties and TPC was found, indicating that phenolic compounds were primarily responsible for the antioxidant properties measured by the DPPH, TEAC, and FRAP assays. Doughs and breads were made using replacements of wheat flour with GSF (0 to 10 g/100g flour) and stored for 0, 2 or 6 weeks at -20°C. Replacement of wheat flour with GSF resulted in a dose dependent increase in the TPC and antioxidant activity of the breads. However, recovery of phenolics was low due to phenolic complexation with proteins during mixing. Consumer acceptance and instrumental analyses were used to investigate the changes in sensory and texture properties due to GSF replacement. An increase in GSF replacement above 5g/100g flour caused the brightness and loaf volume to significantly decrease, while increasing the hardness and number of cells/mm2 in the crumb. GSF replacement did not significantly impact overall consumer acceptance of the breads. However, consumer acceptance of astringency and sweetness significantly decreased as GSF exceeded 5g/100g flour. Based on these results, the replacement of ≤ 5g GSF/100g flour is recommended for the production of fortified breads with acceptable instrumental and sensory properties, and antioxidant activity comparable to antioxidative fruits.

Value-added product development utilizing Washington State grape seed flour

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