Physicochemical Properties of Starches from Four Local Varieties of Millet in Nigeria

Abstract

Purpose: The study was carried out to evaluate the physico-chemical properties of starches from four local varieties of millet in salad cream production. Methodology: Starches were extracted from four varieties of millet, two varieties of pearl millet were used namely Gero and Maiwa (Pennisetum glaucum), Tamba-Finger millet (Eluesine coracona) and Acha-Fonio millet (Digitaria exillis) using dry and wet milling processes for characterization and salad cream production. Standard analytical methods were used in determining the physicochemical properties of the starches. Findings: The various starches physical properties, including colour, Amylose, Amylopectin, Starch Damage and Total Starch of millet cultivars were determined, and significant (p < 0.05) differences were observed among them. Values obtained for Amylose and amylopectin ranged from 24.47 to 26.91% and 73.09 to 74.51% respectively. The amount of starch damage varied from 0.08 to 0.10 % while total starch contained in the various samples ranged from 89.74 to 98.42 %. Proximate composition showed no significant difference among the starches in terms of moisture except in the wet milled Acha with 10 %. Ash content of the starches ranged between 0.79 and 9.22 %. Fat was higher in the control sample 10.22 % and lowest in the wet milled Tamba 1.69 %. Significant differences P<0.005 were found in the protein content amongst the various starches extracted, with Wmg having the highest value of 9.26 %. Crude fibre was in the range of 2.37 and 4.50 %. The Resistant starch was highest in Wmt (79.44%) and lowest in Dma (16.90%). Carbohydrate content was less in the control sample Wmc (62.40%) and highest in Wma (75.29%). Functional properties of various starches such as Bulk density ranged from 0.59% to 0.77%. Water absorption capacity of the starches were between 0.35% and 4.80% with Dmm starch having the lowest and Wmg the highest. Oil absorption capacity of starches varied between 2.10g/ml and 2.80g/ml. while swelling power were 0.43 to 0.91% with Dmc starch recording the lowest and Dmg starch the highest. Solubility values ranged from 9.50 to 24.00% with Dmm and Dmg having lowest and highest respectively. Least gelation capacity varied from 6% to 10%. The pasting characteristics of the four different starches were significantly (p < .05) different. Peak viscosity ranged from 2145.5 to 4379.0 RVU while Trough viscosity ranged from 1311.0 to 3190.0 RVU. Breakdown viscosity ranged from 625.5 RVU to 2401.5 RVU. The Final viscosity varied between 2704.5 and 5495.0 RVU. Increase may be attributed to high carbohydrate content in the different starches. Setback viscosity in this study ranged from 1393.5 to 2633.0 RVU. Peak time measured the peak viscosities in minutes of the cooking time of the starches and it ranged from 4.93 min to 6.30 min. Pasting temperature varied between 75.85°C and 88.40°C. Starches produced from the four local Millet varieties can be utilized for making diverse food products to meet the growing demand for starches in the food industries.