INFLUENCE OF ‘KING OF BITTERS’ (Andrographis paniculata) LEAF INCLUSION ON THE QUALITY CHARACTERISTICS AND ANTIOXIDANT PROPERTIES OF WHEAT- MILLET SUPPLEMENTED BISCUIT

Abstract

The study investigated the influence of the inclusion of varying proportion of Andrographis paniculata leaf flour on the quality characteristics and antioxidant properties of wheat-pearl millet- based biscuits. Andrographis paniculata leaf was harvested from a farm in Akure, Nigeria, while its taxonomical identification was verified at the Forest Research Institute (FRIN), Ibadan, Nigeria, with the herbarium number 112176. Biscuits were prepared using whole wheat flour, whole pearl millet flour, and A. paniculata leaf flour. The recommended combination ratio (50:50) of wheat and pearl millet flour was adopted as the blending baseline while graded levels of A. paniculata leaf flour of 2, 4, 6, 8 and 10% were respectively included in the blending baseline to obtain wheat-pearl millet-Andrographis panniculata flour blends. In the formulation, the inclusion of A. paniculata leaf flour was carried out to replace the wheat and pearl millet flour respectively on equal basis. Each flour blend was used to prepare biscuit using a standard recipe formulation containing: water, shortening, granulated sugar, sweetener, salt, ammonium bicarbonate, and sodium stearoyl-2-lactylate. The results from flour blend evaluation showed that the inclusion of A. paniculata leaf flour generally led to an increase in the crude fibre, crude protein, and ash. However, there was a general decrease in the carbohydrate content as the inclusion of A. paniculata leaf flour increased. The flour blend without the inclusion of A. paniculata leaf flour (WPMF) exhibited the following mineral composition: Ca (90.43 mg/100g), P (218.21 mg/100g), Fe (18.45 mg/100g), Na (38.98 mg/100g), K (217.85 mg/100g), Zn (3.39 mg/100g), Cu (0.60 mg/100g), Co (2.59 mg/100g), and Mn (3.0 mg/100g). However, the mineral composition of the flour blends, as the inclusion of A. paniculata leaf flour increased, showed that a significant increase occurred in calcium (Ca), phosphorus (P), sodium (Na), cobalt (Co), and phosphorus (P), while a significant decrease was similarly observed in iron (Fe), potassium (K), copper (Cu), and manganese (Mn). Lead (Pb) was generally absent in all the flour blends. The inclusion of A. paniculata leaf flour in the blends revealed a significant general increase in water absorption capacity, oil absorption capacity, swelling capacity, and bulk density. However, a general decrease in the foaming capacity, solubility, and least gelation was observed as the inclusion of A. paniculata leaf flour increased. The pasting properties of WPMF (flour blend without the inclusion of A. paniculata leaf flour) exhibited the following values: peak viscosity (658 RVU), breakdown (372 RVU), final viscosity (923 RVU), setback (637 RVU), peak time (5.07 min), and pasting temperature (84.8oC). The inclusion of A. paniculata leaf flour in the blends led to a significant general decrease in all the pasting factors. The proximate composition of biscuits prepared from the flour blends showed a significant increase in crude protein and ash content as well as in energy value when compared to biscuit obtained from flour blend without A. paniculata leaf inclusion. With respect to phytochemicals in the biscuits prepared from the flour blends, significant increase was observed with tannin and carotenoids when compared to biscuits prepared from flour blends containing no A. paniculata leaf. The inclusion of A. paniculata leaf flour in biscuit preparation improved the antioxidant properties of the snack. The ferric reducing antioxidant power (FRAP) increased from 7.40 mg/g (biscuit containing no A. paniculata leaf flour) to 17.82 mg/g in biscuit containing 10% A. paniculata leaf inclusion. The free radical scavenging ability of the snack against 2, 2-diphenyl-1-picrylhydrazyl (DPPH) also increased from about 34% (biscuit containing no A. paniculata leaf flour) to about 60.9% in biscuit containing 8% A. paniculata leaf inclusion. In terms of sensory quality rating of the biscuits, the one containing 2% A. paniculata leaf inclusion was rated the highest in terms of overall acceptability but lower with insignificant difference than biscuit produced without A. paniculata leaf inclusion. The inclusion of A. paniculata leaf flour in the preparation of biscuit had therefore revealed a beneficial influence on crude protein and ash content, energy value, phytochemical composition and antioxidant properties of the snack