Demand-Driven Technologies for Sustainable Maize ... - IITA

442A=(M’-M) x 100/M + A o(1)where A 0represents the initial sample moisture, M and M’ are theweight of the dry solids and the weight of the hydrated samples.The hydration runs were carried out in triplicate and measurementstaken were used to construct the hydration curves. In this study it wasassumed that the internal resistance to water diffusion in grain samplescontrolled the rate of water uptake and hence the internal mass transfercoeffi cients, k 1and k 2. The coeffi cient of water transfer from the grainsurface to the center was defi ned after Peleg (1988) as:M t=M 0+t/(k 1+k 2t) (2)where M tand M 0represent the total water content per unit weight ofdried sample at time t and 0; k 1and k 2are hydration kinetics constants.According to this model, the maximum water absorbed is Mw=M 0+1/k 2and time to reach half-saturation is t 50%= k 1/k 2. The linear absorptionequation of the relation in equation (2) ist/(M t-M 0)= k 1+k 2t (3)Malting studiesThe effects of cultivar and malting conditions on grain properties wereinvestigated in a 3 x 4 x 5 factorial experiment with three hydration levels(50%, 75% and 100%), four maize cultivars (CMS 8501, CMS 8704,Kassaï and 88094xM131xExp24) and fi ve germination times (0, 1, 2,3 and 4 days) as the factors. Maize grains were malted using a micromaltingmethod (Demuyakor and Ohta 1992). After sterilisation (water:ethanol, 30:70 v/v), each grain sample was steeped in distilled water(1:5 w/v, 30 °C) to reach the required hydration level (HL). Randomsamples placed in batches in disposable plates lined with absorbentpaper were allowed to germinate in the dark at 30 °C in an oven(Memmert, Germany) with wetting done twice a day. Duplicate batcheswere taken out at various intervals and dried at 50°C for 48h. Rootletswere rubbed by hand and separated by sieving. The ungerminated(control) and germinated grains were ground in a laboratory mill(SAMAP, Type F100, France) so that they could pass through a 0.5mm sieve. The fl our samples were stored in sealed plastic bags in adessicator until needed for analyses. In a parallel study, 100 grains fromthe steeped samples were germinated on fi lter paper in petri dishes andthe germination activity was recorded (Beta et al. 1995).Malted and raw flour analysisThe water soluble sugars and proteins were extracted according toOshodi and Ekperigin (1989). Each fl our suspension (distilled water, 1:50