Effects of particle size and moisture content on the apparent\viscosity of pastes of some reconstituted indigenous flours.

The study evaluated the effects of particle size and moisturecontent on the apparent viscosity of the pastes of some reconstituted indigenous food flours. The apparent viscosities of the pastes of the reconstituted flours from maize, sorghum and cowpea seeds were determined experimentally. The result showed that the apparent viscosities ranged from 202 to 419 kg/ms in maize; 206 to 425 kg/ms in sorghum and 215 to 459 kg/ms in cowpea. The effect of particle sizes (200, 300 and 425 um) on the apparent viscosity was significant (p< 0.05) and followed a similar trend in all the flour samples. The apparent viscosity had an inverse relationship with the particle size, and increased as the particle size decreased. The effect of moisture  content (8, 10 and 15 %) (wb) on the apparent viscosity was not significant (p < 0.05) as the moisture content levels were too low and in close range to make an appreciable impact on the apparent viscosity. It was further observed that the flours with smaller particle size produced pastes which were more viscous with more suspended and less sedimented or less aggregated particles; and hence are more likely suitable for the processing of most quality traditional foods like Kunu, Tuwo (Hausa); nri-oka, akamu (Ibo); eko, kokoro (Yoruba)

Water absorption kinetics of five varieties of maize as affected by soaking conditions during processing of “Ogi”

This study determined the water absorption kinetics of five varieties of maize (A4W, C3Y, D8W, B2Y and E9W) during soaking for 12 to 96 h at varying soaking temperatures. Water absorption changes were evaluated based on a 5 × 2 × 9 factorial design (varieties × soaking methods×soaking periods). Soaking temperature (20, 30, 40 and 50OC) effects were investigated on the water absorption on a 5 × 4 × 6 factorial design (varieties×soaking temperature × soaking periods). The results revealed that the Peleg constant rate (k1) and capacity constant (k2) were statistically significant (p&lt;0.05) and decreased with increase in soaking temperature. The equilibirium moisture content increased significantly (p&lt;0.05) with increase in soaking temperature while the predicted time to attain equilibirum for B2Y were 49.67, 33.80, 24.58 and 23.73 hours for soaking temperature at 20, 30, 40 and 50oC, respectively. Similar trend was recorded for other maize varieties. The activation energy (Ea) of hydration were 96.06 kJmol-1 (C3Y), 53.60 kJmol-1 (A4W), 47.08 kJmol-1 (E9W), 39.71 kJmol-1 (B2Y) and 31.49 kJmol-1, respectively. Variety D8W with lower activation energy of hydration (Ea), high entropy (ΔS) and free energy (ΔG) was more thermally stable compared with other maize varieties. This study suggested information with beneficial energy saving effect, especicially for design processes and handling equipment for commercial production of “Ogi”.Keywords: Maize, Ogi, Rehydration, absoprtion rate, activation energy, peleg constan

Effect of texture modifiers on the physicochemical and sensory properties of dried fufu

Published online: 1 Oct 2005Glycerol monostearate (GMS) and monoglyceride phosphate (MGP) were added to fufu flour at different levels (0.5%, 1.0% and 1.5%) in hydrated and powdered form. There were evaluated the effects of those additives on physicochemical and sensory properties of dried fufu. Addition of GMS and MGP had a significant effect on the swelling power, solubility, pasting properties and sensory quality of fufu flour. Results obtained were: Dispersibility (69%-70.33%), water absorption index (WAI, 47.7%-54.4%), least gelation concentration (LGC, 4.67%-6.67%) and water absorption capacity (WAC, 119.3%-136%) for the fufu flour treated with GMS and MGP. Solubility of the samples mixed with the powdered form of the modifier ranged between 23.2% and 31.7%, while that of the samples mixed with the hydrated form of GMS and MGP ranged between 5.3% and 12.7%. The pasting time varied between 8.25min and 18.50min, fufu flour mixed with 1.5% GMS powder had the lowest value while that mixed with 1.0% MGP powder and 0.5% hydrated MGP recording the highest value. Pasting temperature ranged from 67.00°C to 72.00°C, with flour mixed with 1.0% hydrated GMS and 0.5% GMS powder having the lowest and highest value, respectively. The highest value of peak viscosity (762.50BU) was recorded by fufu flour containing 1.0% hydrated GMS. The lowest value of starch stability (255.50BU) was recorded by fufu flour without modifier while the highest value (499.00BU) was recorded by fufu flour containing 0.5% GMS powder. There were significant differences (p 0.05) in the sensory qualities except for colour of fufu flour samples. The overall quality index (OQI) comprised between 5.24 and 6.01, fufu sample containing 0.5% hydrated GMS had the lowest OQI and that containing 1.0% hydrated MGP the highest OQI. Addition of 0.5% texture modifier to dried fufu may be economically feasible according to the estimated cost of production

Physicochemical properties of extrudates from white yam and bambara nut blends

This study was conducted to investigate effects of extrusion conditions on physicochemical properties of blend of yam and bambara nut flours. A blend of white yam grit (750 jim) and Bambara nut flour (500 (tm) in a ratio of 4:1, respectively was extrusion cooked at varying screw speeds 50-70 r.p.m., feed moisture 12.5-17.5% (dry basis) and barrel temperatures 130-150°C. The extrusion variables employed included barrel temperature, screw speed, and feed moisture content, while the physicochemical properties of the extrudates investigated were the expansion ratio, bulk density, and trypsin inhibition activity. The results revealed that all the extrusion variables had significant effects (p<0.05) on the product properties considered in this study. The expansion ratio values ranged 1.55-2.06, bulk density values ranged 0.76- 0.94 g cm"3, while trypsin inhibition activities were 1.01-8.08 mg 100 g"1 sample

Changes induced by soaking period on the physical properties of maize in the production of Ogi

This study was aimed at investigating the effect of soaking method and period on some selected physical properties on maize varieties. Five varieties of maize (A4W, C3Y, D8W, B2Y and E9W) were soaked for 12–96 h at ambient temperature of 28 and average hot temperature of 65°C as generally praciticed in the production of Ogi from cereals. Some selected physical properties were evaluated based on a 5 × 2 × 9 factorial design (varieties × soaking methods × soaking periods). The reseult revealed that the linear dimensions of the five varieties of soaked maize increased with increase in linear dimensions up to about 36th hour of soaking. The percentage increase in width was in the range of 5.482–9.67%, 4.064–8.25%, 3.76–6.81% and 0.88–1.81%, for C3Y, B2Y, D8W, A4W and E9W for both soaking conditions, respectively. Significant difference (p  0.05) in the values obtained for sphericity at soaking condition of 65°C compared with soaking at 28°C. This study showed that the period of soaking had significant effect (p < 0.05) in increasing the overall dimensions of maize grains up to 36th hour and thereafter witnessed an irregular pattern

Deep fat frying of yam slices: optimization of processing conditions using response surface methodology

The deep-fat frying of yam slices was investigated with the aim of optimizing the processing conditions. During frying, frying temperature, initial dry matter and frying time have a significant effect on moisture loss and oil uptake. Response surface methodology central composite rotatable design was used to study the effects of the independent variables on quality attributes of yam chips. Breaking force, oil content, moisture content and color parameters were determined. Statistical analysis with response surface regression showed that breaking force, oil and moisture contents and color parameters (L* and a*) were significantly (P < 0.05) correlated with frying temperature, initial dry matter and frying time. The optimum conditions were a frying temperature of 175–180C, using tubers of initial dry matter of 0.179–0.214 kg/kg with a frying time of 4–5 min. It was suggested that the regression equation can be used to estimate the dependent variables for fried yam chips except b* (yellowness) parameter

Effect of etrusion variables on Extrudates properties of water yam flours - a response surface analysis

Water yam (Dioscorea alata) flour was processed using standard wet milling procedure prior to the extrusion process, which led to the determination of extrudate properties of the flours. A single-screw extruder (DCE 330, NJ) was used in evaluating the extrudate properties, which included torque, mass flow rate, residence time, specific mechanical energy and expansion ratio of the flours from the water yam samples. The effect of extrusion and process variables: feed moisture content, screw speed and barrel temperature on the extruder torque, residence time, mass flow rate, specific mechanical energy and expansion ratio for the variety were determined and predictive models were also developed using response surface methodology. It was observed that changing the feed moisture content, barrel temperature and screw speed significantly (P < 0.05) affected expansion ratio, torque, mass flow rate, residence time and specific mechanical energy of all the extrudates. Increasing the feed moisture content (18–28% db) and screw speed (80–180 rpm) resulted in a substantial decrease in expansion ratio (46.6%), residence time (27.5%) and specific mechanical energy (83.6%); whereas, increasing the screw speed significantly increased the mass flow rate (64.5%) of extrudates. Regression analysis indicated that screw speed and feed moisture content were the major process variables showing significant (P < 0.05) linear, quadratic and interaction influences on mass flow rate, expansion ratio and specific mechanical energy