Antioxidant properties and consumer acceptability of pearl millet - tiger nut biscuits

Purpose - This paper aims to focus on the antioxidant properties and consumer acceptability of biscuits produced from pearl millet (PM)-tiger nut (TN) composite blends, with the aim of encouraging the use of these under-utilised food crops in producing value-added products with nutraceutical potential. Design/methodology/approach - PM grains and TN seeds were processed into flour and blended at ratios:15:85 (A), 20:80 (B), 25:75 (C), 30:70 (D), 35:65 (E), 40:60 (F), 45:55 (G), of PM to TN using response surface methodology. The antioxidant properties of the biscuits produced from the flour blends were determined using standard methods, and data obtained were subjected to analysis of variance (ANOVA); differences of means were separated using Duncan multiple range test. The biscuits were subjected to sensory evaluation using 50 untrained panellist and results statistically analysed. Findings - The total phenolic content (TPC-mg/GAE) of PM-TN flour blends ranged from 2.65-4.95 (A-G), with an average TPC of 3.85. In PM-TN biscuits, total phenolic values ranged from 1.20-3.42 (A-G), with an average of 2.39. The 2,2'-azino-bis(3-ethyl benzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activities (mu molTEAC/g) of PM-TN flour blends ranged from 26.7-36.4 (A-G), and the values for biscuits ranged from 28.5-38.6 (A-G). There was a highly significant correlation, r = 0.811(p < 0.001) and r = 0.913 (p < 0.001) between phenolic content and antioxidant activity for flour and biscuit, respectively. The effect of in vitro digestion of biscuits on the antioxidant assays viz-a-viz:TPC and ABTS radical scavenging activities were also investigated. The order of phenolic release was enzymic > aqueous > ethanolic digest for TPC, while for ABTS, the order of release was enzymic > ethanolic > aqueous. The highest values for antioxidant properties were found in the simulated in vitro enzyme digested biscuits. Consumer acceptability revealed that the overall acceptability scores of the biscuits were not significantly different except for biscuit sample G. Originality/value - The paper has demonstrated the antioxidant potentials and consumer acceptability of PM-TN biscuits. It also shows the effect of in vitro digestion on the antioxidant activities of the biscuit and its potential health benefit, as a source of antioxidant.