Yam

The  specific  heat  capacity of  any  tuber  crop  is  an  important  thermal  property that  significantly influences the analysis of processing and storage system as well as the determination of thermal rate  processes.  The  specific  heat  of  yarn  and  cocoyam  was  determined  at  various  levels  of moisture  content  and  temperature  using  a  5  by  5  factorial  design  in  CRD.  For  both  crops,  the specific heat increased with increase in moisture content and temperature but the incremental rate reduced at moisture content above 30%. A regression analysis performed on the generated
data gave a functional relationship between the variable for yam and cocoyam.

Yams are not among the most common sources of industrial starch, which are mostly imported at a cost. Exploiting alternative sources of starch would lessen the burden of its importation. Starches from four local varieties of Dioscorea rotundata namely Pona, Labreko, Asobayere and Muchumudu were analyzed for their physicochemical and functional properties. Results obtained showed significant differences (p<0.05) in some physicochemical properties (moisture, ash, starch yield and pH). Moisture, ash, starch yield, pH, amylose, amylopectin, swelling power, solubility and water binding capacities ranged from 7.22 to 7.82%, 024 to 0.86%, 12.61 to 20.89%, 5.57 to 6.25, 27.48 to 31.55%, 68.45 to 72.52%, 10.57 to 12.48%, 8.52 to 9.32% and 175.25 to 182.69% respectively. Asobayere had the highest starch yield (20.89%) and may be exploited for starch production. There were significant differences (p<0.05) in the pasting properties. The pasting temperature ranged from 75.10 (Asobayere) to 77.30°C (Muchumudu). Peak temperature ranged from 81.7 (Asobayere) to 94.8°C (Muchumudu). Peak viscosity for Asobayere, Pona, Labreko and Muchumudu were 726, 614, 685 and 639 BU respectively. Final viscosity ranged from 385 (Pona) to 817 BU (Muchumudu). Values of 385 (Asobayere), 142 (Labreko), 293 (Pona) and 25 BU (Muchumudu) were observed for breakdown viscosity. Labreko had the highest value of 337 BU and Pona the lowest value of 79 BU for setback viscosity. Muchumudu may be used industrially in products that require high unit yield, low viscosity and paste stability at low temperatures. Asobayere and Labreko may be used for foods that require thick and cohesive paste such as fufu and pounded yam due to its high pasting viscosities. Yam starches can be exploited for diverse uses.

Successful use of tissue culture to propagate Dioscorea spp. depends on maximizing subsequent growth in vivo. This paper describes the growth of in vitro plantlets of the Jamaican yams D. trifida L. cv. Short Neck Yampie (SNY) and D. cayenensis Lam. cv. Round Leaf Yellow Yam (RLYY) after transfer to in vivo conditions, from day zero (day of transfer) to harvest of the first generation tubers at 314 d, and sprouting of these tubers. As the SNY and RLYY plants grew in vivo, abrupt changes occurred in the type of shoot (changed from type I to type II) and underground organ (from primary nodal complex to tuber), and in the rates of stem and root growth. Gradual changes occurred in the number of roots. The first observable morphological feature of the SNY and RLYY plants to change was the shoot tip. This changed from a lateral position at the node at the base of a terminal leaf (lateral tip), to the shoot apex (apical tip). It is suggested that the change in shoot tip position and associated features mark the transition from a juvenile phase to an adult vegetative phase. The shoot tip position changed earlier on plantlets that had the greater number of roots at day zero (RLYY), and earlier from heavier first generation tubers (SNY). A decrease in the length of the juvenile phase of micropropagated RLYY plants by 14 d resulted in a heavier tuber yield but did not affect tuber numbers. The significance of these results on the propagation of Dioscorea is discussed.

Yam is a major economic crop that plays a significant role in food security and poverty alleviation in Ghana. Despite this role of yam in Ghana, farmers have incessant difficulty in accessing adequate planting materials for cultivation. In order to understand this problem, this research was conducted to determine the various factors that can influence the accessibility of yam planting materials to farmers in the Techiman District of the Brong Ahafo Region of Ghana. Quantitative and qualitative research techniques including semi-structured interviews and observations were employed for this study. The research identified six main factors as critical to accessing yam planting materials in the study area. These included the cultivar of yam that farmers want to grow, access to capital to purchase planting materials, and availability and cost of transportation to convey planting materials to store at farmer homes. The others were pests and diseases infestation of planting materials in sto...

In West Africa, yam can be an important crop to reduce poverty and hunger if Research and Development measures identify and properly engage its key production factors for enhanced outputs and better income. Data from 1400 households in Ghana and Nigeria were collected in a multistage random sampling survey (and complementary data from 76 farm family fields) with a structured questionnaire and qualitative interview questions. The results showed that yam is producedmainly with crude inputs/technologies to reduce high dependence on labour, seed production and control of pests and diseases. Yam is produced widely with purchased inputs including seed yam and hired labour; chemical fertiliser, herbicide and pesticides are less often used. Analyses of determinants of use of purchased inputs reveal three serious impediments to expansion in yam production: the increasing scarcity and high cost of hired labour, shortage of suitable land and poor farm roads. As employment opportunities for uns...