ABSTRACT

Starches were produced from sorghum and maize grains. The starches were

tested for purity. They were modified using the following reagents and enzymes

glucoamylase, c - amylase, ,8— amylase, 0.5% MCI, 1.0% HC1, combination of 0.5% HC1 +

fi — amylase, cc + /3— arnylase, 0.5% 1-JCI + glucoamylase. The least gelation concentration,

water absorption capacity, bulk density, solubility in water swelling index and viscosity of the

modified starches and the native starches were determined. Sensory evaluation studies were

carried out on biscuits baked with maize/wheat and sorghum/wheat composite flours (25:75%

ratio) containing 3.75% maize and sorghum starches modified as described above.

Based on the initial sensory evaluation results, selected modified starches were incorporated

into maize/wheat and sorghum/wheat composite flours. The flours were aged for 10 weeks.

Biscuits were baked from them and subsequently subjected to further sensory evaluation

studies.

The percentage yield of maize and sorghum starches were 54.04% and 47.54% respectively.

Different modification processes affected the perccntage recovery of the modified starches.

Modification with acids or enzymes/acids led to lower recovery (70.50 — 79.7%) of the treated

starches than other treatments (80 — 88.57%). The least gelation concentrations of the

glucoarnylase modified starch samples were lower 1 .0%w/v than those of the native starches

2.5%w/v. The peak viscosity of the acid modified maize starch was lower (18BU) than the

unmodified sorghum starch (294BU). Incorporation of modified starches into composite flours

increased the sensory quality of the biscuits produced in terms of texture and overall

acceptability. Ageing resulted to marked changes in the organoleptic properties of the baked

products.