Quality Evaluation of Vegan Gluten-Free Cookies from Sorghum and Purple Sweet Potato Flours

Toh, Hui Jia (2021) Quality Evaluation of Vegan Gluten-Free Cookies from Sorghum and Purple Sweet Potato Flours. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Incorporation of purple sweet potato flour into sorghum flour for the developing of vegan gluten-free cookies is putting the effort to increase the nutritional quality in cookies. The objectives of this research were to investigate the effect of purple sweet potato flour on physical characteristics, total phenolic content, antioxidant content and proximate composition of cookies and to determine the sensory characteristics and consumer acceptability on cookies incorporated with purple sweet potato flour. Cookies were prepared by substituting sorghum flour with 0% (Control), 10% (Sample 1), 30% (Sample 2) and 50% (Sample 3) of purple sweet potato flour. Physical characteristics (width, thickness, spread ratio and weight), color, texture, total phenolic content (TPC), antioxidant content, proximate composition analysis were determined. Sensory evaluation was conducted using 9-hedonic scale test and preference test. Appearance, aroma, taste, color, texture, overall appearance of each cookies were evaluated. By comparing to the control cookies, purple sweet potato incorporated cookies had lower L* value, higher a* value and lower b* value. Purple sweet potato cookies had higher hardness, TPC, antioxidant content, ash content than control cookies. However, control cookies had higher protein content compared to purple sweet potato cookies. Sample 3 (50% purple sweet potato flour) had the significantly highest total phenolic content (14.31 mg GAE/100 g), antioxidant content (40.89 mg AAE/100 g), ash content (2.60%) and significantly lowest protein content (6.40%) (P < 0.05). For sensory evaluation, there is significant differences on aroma, taste, color, texture and overall acceptance (P < 0.05) for each cookies samples, except for appearance (P > 0.05). Sample 1 that incorporated 10% of purple sweet potato flour was the most preferable (44%) cookies among other cookies. It is concluded that there is a great potential to incorporated purple sweet potato into cookies to increase the overall quality and nutritional value.