Physicochemical properties of modified trifoliate yam starches
Physicochemical properties of modified trifoliate yam starches were determined. Trifoliate yam starches were harvested and the starch was extracted. The extracted starch was modified using four methods (acid and alkali treatment, oxidation and acetylation). Colour and physicochemical properties of the modified starches were determined. Colour of pre-gelatinized trifoliate yam starch was significantly different (p<0.05) from other starches. The colour was yellowish/reddish while other starches were lighter in colour. The structures of untreated, oxidized, pre-gelatinized and acetylated starches were polygonal in shape. Granule sizes of native and modified trifoliate yam starches ranged from 2.53 to 3.86 μm. Amylose content of trifoliate yam starches ranged from 10.01 to 16.17%. Swelling power of pre-gelatinized starch increased from 2.15 at 60o C to 3.00 at 70 oC but the values decreased at 80 to 90o C. Acid-treated starch exhibited higher paste clarity at refrigerated temperature than ambient temperature but at ambient temperature, oxidized starch had high paste clarity during storage. Acid and alkali-treated starches had higher water exudate at day 0 which later decreased with storage. Acetylated starch had higher peak viscosity (3833.00 cP). Acid and alkali treatment reduced the viscosities and had low freezethaw stability.
Keywords: Colour, Modification, Physicochemical, Trifoliate yam starch