| Cookie is one of nonperishable but unhealthy baked foods because it is high in fat and sugar content but low in bioactive compounds and dietary fiber. However, cookie can be made healthier by fortification using bioactive compounds and fiber rich ingredients. Grape seed flour (GSF) is rich in dietary fiber and polyphenols and could be used to fortify sugar cookies. The objective of this study was to evaluate the effect of quantity and particle size of GSF on the physicochemical properties (such as diameter, thickness, color and hardness), chemical composition (proximate composition, dietary fiber and polyphenol contents) and oxidative stability of cookies. The peroxide value (PV) and P-anisidine value (P-AV) were measured as indicators of early and late stages oxidation, respectively. The dry seeds of Muscadine Noble grapes were grounded into flour fractions with average particle size of 104 and 209 microm, respectively. Each fraction of GSF was added to sugar cookie formula to 2.5 and 5%. The cookie without GSF was used as control. The study found that incorporation of GSF resulted in concentration-dependent decrease in moisture and total carbohydrate contents (P<0.05), significant increase in protein, ash and total dietary fiber contents of cookies (P<0.05), but did not change the fat content. The moisture content of cookies was also affected by particle size of GSF (P<0.05). The contents of polyphenols including total phenolics, total flavonoids, and condensed tannin of cookies increased with GSF in dose-dependent manner and decreased as particle size of GSF increased (P<0.05). As GSF content increased and particle size decreased, the cookie became darker, thicker and harder, while cookie diameter became smaller. However, the addition of GSF did not inhibit the oxidation of cookies as expected because PV and P-AV of cookies containing GSF were much higher than those of control and increased with GSF content. In addition, smaller particle size contributed to higher PV and P-AV. This study demonstrates that fortification of cookie with GSF increased the dietary fiber and polyphenol contents, but also caused some adverse effects on cookies. Therefore, care must be taken when using GSF as food ingredient. More study is needed to identify whether the unsaturated fat or polyphenol is responsible for higher PV and P-AV of cookies during baking and storage, and to explore other applications of grape seeds. |
