UTILIZATION OF ACHA (Digitaria exilis Stapf) FLOUR AND STARCH IN FOOD APPLICATIONS

Abstract

The objective of this study was to determine the functionality of acha flour and starch in their native and modified forms and produce biscuit with a blend of the flour, mango kernel seed and soy cake flours as well as produce yoghurt with skimmed milk using the native and modified acha starch as stabilizer. Acha was purchased locally from king’s market Kaduna, Nigeria, and processed into flour. Certain portions were modified chemically (acetylation) and enzymatically while starch was extracted from other portions and also modified. The native and modified flours were combined with mango kernel seed and soy cake flours to make composite flours using predetermined ratios. Composite flours with four different ratios were generated to make a sum of twelve ratios. The flours were analyzed for proximate composition, colour, minerals, functional, pasting and microstructural properties while the starches were analyzed for physicochemical, rheological and structural properties in addition to the parameters analyzed on the flours. The modified flours were of good nutritional and structural qualities. The protein content of the flours ranged between 3.73 and 4.90% with increased protein content in the modified flours. Highest values of zinc (5.87 mg/100g), calcium (860.48 mg/100g), copper (1.44 mg/100g) and phosphorus (301.90 mg/100g) were observed in the native acha flour while enzymatic modification brought about an increase in iron (19.81 mg/100g), Manganese (2.60 mg/100g) and potassium (53.94 mg/100g). Additional functional groups were observed in modified flours such that while the native acha flour had 14 peaks, the acetylated and enzymatically modified flours had 24 and 23 peaks, respectively. The acetylated and enzymatically modified starches had improved proximate composition with reduced protein content of 0.55% and 0.43%, respectively compared with the native starch which had 0.74%. They also had commensurate functional properties with water absorption capacity of 1.94 mg/g and 2.07 mg/g, respectively compared with the native starch having 1.55 mg/g. The blended samples were also analyzed for proximate composition, minerals, pasting, functional, antioxidants and anti-nutritional properties. The sample containing 70% acha flour, 20% mango kernel seed flour and 10% soy cake flour was selected from each blend of native and modified samples formulated because they had lower anti-nutritional content and commensurate nutritional, functional, pasting and antioxidant properties and then analyzed for microstructural properties. The protein content of the chosen native acha composite flour was 13.37% while that of the acetylated and enzymatically modified acha composite flours were 15.14% and 12.50%, respectively. The total phenol content of the chosen native, acetylated and enzymatically modified acha composite flour were 9.34, 5.81 and 9.23 mgTAE/g, respectively while the oxalate contents were 0.99, 1.04 and 1.13 mg/g, respectively. The most abundant mineral present in the biscuits produced was potassium and they also had improved nutritional properties, colour, antioxidants, texture profile, in-vitro starch digestibility and in-vitro glycemic index compared with wheat flour biscuits. The protein content of biscuit samples from modified acha flour were higher than the native acha composite biscuits and had values ranging between 9.65 to 10.51%. The native and modified acha starch were also used in the production of yoghurt and analyzed for physicochemical, colour, microbial and sensory characteristics. The yoghurt samples from the modified acha starch compared favourably with commercial yoghurt and both biscuit and yoghurt had reduced microbial load.