Effect of moisture on selected physical properties of “padi-tuya”and“songotra”cowpea varieties

This study assessed the effect to forrewetting and drying on some selected physical properties of two cowpea varieties namely-Padi-Tuya and Songotra at eight selected moisture contents namely,9.8, 12.6, 16 and 23%w.b.forrewetting;and8.4,13.2,17.30and22%w.b.fordrying. Inthemoisturecontentrangeof9.8%w.b.to23.0%w.b., the length, width and thickness of Padi-Tuya increased non-linearly from 9.72mm to 10.54mm, 6.84mm to 7.15mm and 5.29mm to 5.4mm respectively. The length, width and thickness of Songotra increased non-linearly from 6.98mm to 7.68mm, 5.21mm to 5.99mm and 4.03mm to 4.45mm respectively. Padi-Tuya recorded non-linear increases for geometric mean diameter (7.05mm to 7.41mm), surface area (156.32mm2 to 172.49mm2) and volume (183.78mm3 to 213.02mm3).Geometric mean diameter, surface area and volume for Songotra increased non-linearly from 5.27mm to 5.90mm, 87.29mm2 to 109.23mm2 and 76.69mm3 to 107.35mm3respectively.Bulk densities of Padi-Tuya and Songotradecreased non-linearlyfrom796.33kgm-3 at 9.8%wb to 751.56kgm-3 at 23.0%wb and 807.91kgm-3 to 728.06kgm-3 respectively. Padi-Tuya and Songotra had their true densities decreasingnon-linearlyfrom1210.00kgm-3 at 9.8%wb to 1187.30 at 23.0%wband 1217.61kgm-3 to 1206.54kgm-3 respectively. For porosity,Padi-Tuyaincreased from 51.95% at 9.8%wb to 57.98% at 23.0%wb and Songotra increased from 33.67% to 39.65%.The 1000 Grain mass for Padi-Tuya increased non-linearly from 225.03g to 236.05g and Songotra increased from 140.21g to 150.63g.Padi-Tuya had static coefficient of friction increasing non-linearly on all three surfaces namely plywood (0.29 to 0.35), mild steel (0.37 to 0.59) and rubber (0.35 to 0.48). The static coefficient of friction for Songotra increased non-linearly on all the three surfaces namely plywood (0.31to0.39), mild steel(0.38to0.46) and rubber(0.39to0.47).The results obtained for drying showed the following trends: With decreasing moisture content, length, width and thickness dimensions decreased from 7.91 to 6.97mm, 10.53 to 9.69mm, 7.12 to 6.79mm and 5.43 to 5.26mm respectively for Padi-Tuya,and7.61 to 6.96mm, 5.94 to 5.19mm and 4.44 to 3.99mm respectively for Songotra. Padi-Tuya had geometric mean diameter, surface area and volume decreasing from 7.38mm to 7.01mm, 171.27mm2 to 154.28mm2 and 210.71mm3 to 180.15mm3 respectively while that of Songotra decreased non-linearly from 5.85mm to 5.24mm, 107.66mm2 to 86.39mm2 and 105.04mm3 to 75.51mm3 respectively under drying conditions.Bulk density increased non-linearly from692.52kgm-3 to 701.79kgm-3 and 727.98kgm-3to 801.55kgm-3withfor Padi-Tuya and Songotra respectively. True density increased non-linearly from1197.67kgm-3 to 1219.78kgm-3 and1201.63kgm-3 to 1222.00kgm-3Padi-Tuya and Songotra respectively. Porosity increased non-linearly from 42.18% to 42.47% for Padi-Tuya. It however decreased from 39.42% to 34.41% for Songotra.1000 grain mass decreased non-linearly from, 151.08g to 138.69g and 153.79g to 125.72g for Padi-Tuya and Songotra respectively. Filling angle of repose decreased non-linearly from 29.90 to 17.250 and 28.40 to 21.480for Padi-Tuya and Songotra respectively. Padi-Tuya recorded a non-linear decrease in static coefficient of friction on all three surfaces namely plywood (0.35 to 0.28), mild steel (0.54 to 0.37)and rubber (0.48 to 0.34). Highest coefficient was recorded for mild steel followed by rubber and then plywood. Songotra also recorded decreases on the three surfaces; ply wood(0.39to0.31),mild steel(0.46to0.37)and rubber(0.46to0.36) during drying. For both conditions, rubber offered the maximum friction followed by mild steel and then plywood.

Source: KNUST