Biscuits are wheat flour-based manufactured food products. Another option is to locate a flour substitute, such as plantain flour or purple rice. This study aims to establish the ideal ratio of purple rice flour and plantain flour based on the quality attributes of biscuits. This study employed a one-factor, Completely Randomized Design (CRD) with five treatment levels and three replications. The observational data were analysed using ANOVA with the DNMRT further test at a 5% significant level. The treatment in this study compared purple rice flour and plantain flour to prepare biscuits. The ratio of purple rice flour to plantain flour had a very significant (p <0.01) effect on water content (3.56%), ash content (2.11%), fat content (25.18%), crude fiber content (17.85%), protein content (4.72%), and carbohydrate content (61.49%), but no significant effect (p >0.01) on antioxidant activity (55.83%). Except for protein, all treatments meet the SNI's requirements for biscuit quality. Based on the organoleptic test of taste, aroma, texture, and colour preferred by panellist with score of A (90-10) 3.52%, B (80-20) 3.97%, C (70-30) 4.42%, D (60-40) 5.03%, and E (50-50) 5.52% were obtained. The best-quality biscuits were in treatment E. (comparison of purple rice flour and plantain flour 50:50).

This study aimed to determine the effect of substitution of wheat flour with purple sweet potato flour on the end-quality and antioxidant activity of the resulting roll cakes. Furthermore, the objective was to determine the optimal percentage of the substitution of wheat flour with purple sweet potato flour that would be graded as the best and most preferred by the panelists. This study used a completely randomized design (CRD) with 5 treatment levels and 3 replications. Observational data were analyzed using analysis of variance (ANOVA) and Duncan's New Multiple Range Test (DNMRT) at 1% significance level. The treatment in this study was the substitution of purple sweet potato flour for wheat flour in the manufacture of roll cakes, namely 20, 30, 40, 50 and 60%. The results showed that the substitution of purple sweet potato flour for wheat flour in the production of sponge rolls had a very significant effect on the content of water, ash, fat, protein, crude fiber, carbohydrates, and had no significant effect on antioxidant activity. The most preferred sponge cake was treatment E (substitution of purple sweet potato flour for 60% wheat flour) with a moisture content of 8.65%, ash content of 1.19%, fat content of 17.41%, protein content of 10.18%, crude fiber content 19.23%, carbohydrate content 62.56%, and antioxidant activity 62.47%.