Quality characteristics and antioxidant activity of rice cookies with grapefruit peel powder

This study evaluated the quality characteristics and antioxidant activity of rice cookies supplemented with grapefruit peel powder (0, 5, 10, and 15%). Density and spread factor did not differ significantly among rice cookies, whereas pH decreased from 6.94 to 5.66 with increased grapefruit peel powder (p<0.05). The water content decreased slightly with the addition of powder (from 2.40 to 1.86%), and color measurements indicated reduced lightness accompanied by increased redness and yellowness. Hardness significantly increased from 7.56 to 12.33 with a higher powder incorporation (p<0.05). DPPH and ABTS radical scavenging activities increased from 14.01 to 55.07% and from 11.34 to 60.37%, respectively, as the powder level increased (p<0.05). In a consumer preference test, cookies containing 10% grapefruit peel powder achieved the highest scores for flavor, texture, and overall acceptability. These findings indicate that grapefruit peel, a by-product of pulp processing, represents a promising upcycled ingredient with antioxidant functionality in rice-based bakery products