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
Kim et al. (Sat,) studied this question.