O.O. Ajibola

Thermodynamics of moisture sorption in melon seed and cassava

Experimental data on the sorption isotherms of melon seed and cassava were used to determine their thermodynamic functions (heat of vaporization, spreading pressure, net integral enthalpy and net integral entropy). The heat of vaporization of both products decreased with increase in moisture content and that of melon seed approached the latent heat of pure water at a moisture content of about 13% dry basis, while that of cassava approached it at a moisture content of about 36% dry basis. The spreading pressure of both products decreased with increase in temperature and increased with increase in water activity more markedly in the high range of water activity (aw>0.6). The net integral enthalpy of melon seed decreased from a value of 847 kJ/kg as the moisture content increased from 3.2% (db). The trend became asymptotic at a value of 161.7 kJ/kg as the moisture content of 10% (db) was approached. The net integral enthalpy of cassava increased with moisture content to a maximum value of 770 kJ/kg at 10.70% (db) moisture content, and declined. The net integral entropy of melon seed increased with moisture content while that of cassava decreased to a minimum of value at 12% (db) moisture content and increased. The differences in values and trend of the thermodynamic properties of melon seed and cassava were attributed to chemical adsorption, structural modification of the adsorbent, and presence of oil and more polar groups in melon seed and presence of starch in cassava.

Sorption equilibrium and thermodynamic properties of cowpea (Vigna unguiculata)

Equilibrium relative humidity (ERH)–moisture content data for cowpea (Vigna unguiculata) at five different temperatures (40, 50, 60, 70 and 80 C) and moisture content values ranging from 4.5% to 22.2% (dry basis) were determined using the vapour pressure manometric method. A non-linear least squares regression programme was used to evaluate four moisture sorption models. The modified Henderson model gave the least standard error of estimate of 5.8% for ERH and 1.3% for equilibrium moisture content (EMC), as a result, this model was considered to be the best for predicting the ERH and EMC of cowpea. The experimental data was also used to determine the thermodynamic functions of cowpea. Latent heat of vaporization decreased with increase in moisture content and approached the latent heat of pure water at the moisture content of 24% (dry basis). The spreading pressure increased with increase in relative humidity but decreased with increase in temperature more remarkably in the high range of relative humidity (RH > 0:65). Net integral enthalpy decreased with moisture content and the trend became asymptotic as the moisture content of 18% was approached. Net integral entropy was negative in value and it increased with increase in moisture content in the moisture range of 4–6.4% dry basis. It thereafter, remained constant until the moisture content of 14.2% was reached, and then it continued to increase with increase in moisture content. 2003 Elsevier Science Ltd. All rights reserved.

Thin-layer drying of melon seed

Abstract Moisture equilibrium data and thin-layer drying rates for melon seeds at different temperatures (40°C–70°C) and relative humidities (10%–88%) were determined using static gravimetric methods. A nonlinear leastsquares regression program was used to evaluate five desorption isotherm models and three thin-layer drying models. The modified Halsey model gave the least standard error of estimate of 0·4% for equilibrium moisture content and 4·8% for equilibrium relative humidity. None of the three thin-layer drying models used to evaluate the thin-layer drying results was significantly better than the others in predicting drying. The exponential model in which the drying constant is a function of temperature and relative humidity was found adequate for predicting thin-layer drying of melon seed.

The effects of soaking and cooking time on the cooking properties of two cowpea varieties

The effects of soaking and cooking time on water absorption capacity, cookability, percent split, and texture of two varieties of cowpea, IITA-2246 and IFE-BPC, were investigated. Soaking prior to cooking had an effect only on the cookability, while the amount of water absorbed and the penetration depth (a measure of texture) of a penetrometer head in the seeds increased with cooking time. The properties were found to differ notably for the two varieties with IITA-2246 having a softer texture than IFE-BPC. Splitting in cooked beans increased with cooking time with maximum of 92% split in IITA-2246 and 63% split for IFE-BPC. Higher temperature soaking reduced the cooking time of both varieties.

Comparative evaluation of the digester–screw press and a hand-operated hydraulic press for palm fruit processing

Abstract In order to demonstrate the strength and possible weaknesses of the digester–screw press (DSP) system for small-scale oil palm fruit processing, a comparison was made of its performance and that of the erstwhile hand-operated hydraulic extraction system. Indices of evaluation include oil yield and quality, and operational economics. The results indicate that the throughput of the DSP system was four folds of that of the hydraulic system, whilst also operating at higher oil extraction efficiency (89.1%). There was no significant difference between the quality of the palm oil obtained from the two systems. However, the economic analysis of the systems indicates that at throughput of 0.75 t/h and above, the DSP system was more economical than the hydraulic system in terms of equipment, labour, material and floor space requirement and revenue accruing from the processing operation.

Regression relationships for the soaking and cooking properties of two cowpea varieties

Abstract Water absorption and penetration depth (a measure of texture) of two cowpea varieties as influenced by varying soaking time (0.15–6 h) and soaking temperature (28–75 °C) were determined. The effects of different soaking treatments prior to cooking and cooking time on percent split, drained weight and the penetration depth of the cooked cowpeas were also investigated. The aim of the study is to establish mathematical relations between the product characteristics by regression statistics. Water absorption correlated positively with soaking time but the goodness of fit was temperature and variety dependent. Poor correlation coefficients were obtained when the penetration depth of the seeds was expressed as a sole (linear) function of soaking time or amount of water absorbed. However, equations involving both variables described the penetration depth of soaked cowpeas better. Cooking time correlated very well with drained weight (0.883 ≤ r ≤ 0.979), percent split (0.797 ≤ r ≤ 0.962) and penetration depth of cooked seeds (0.895 ≤ r ≤ 0.982). Equations involving drained weight and cooking time as variables were developed to predict the penetration depth of cooked cowpeas. The degree of fit increased with the inclusion of the product or higher order terms (0.841 ≤ r ≤ 0.996).

Technological assessment of palm oil production in Osun and Ondo states of Nigeria

Abstract The potential economic returns from the oil palm are high if processed with efficient technologies. This study was undertaken to evaluate the technologies in use for the production of palm oil from a gender perspective. A survey was conducted in Osun and Ondo States of Nigeria using a structured questionnaire and the participatory learning approach. A total of 28 palm fruit processing centres were surveyed. The various technologies available in the field for each unit operation were evaluated using certain criteria. Palm oil production is dominated by female processors and male assistance is sought in operating the machines and in carrying out strenuous tasks. Only two of the unit operations (digestion and extraction) have been partially mechanised while the other processes (quartering, stripping, sterilising, and clarifying) are performed manually. None of the machine operators interviewed had any formal training in machine operation and maintenance but they perform these tasks after learning by observation. The result of this study indicates an urgent need for establishing a training program both for machine operators and the maintenance personnel. There is no organised drainage system in the palm oil processing centres except at the industrial mills. Waste water is disposed of in surrounding bushes. The traditional technologies exposed the processors to the vagaries of the weather and other operational hazards. The technology profile proposed for the various unit operations is that of modest but accessible changes that work within the existing system and could be adopted by large numbers of women.

Thermal properties of ground and hydrated cowpea

Abstract The effects of temperature (50–80 °C) and moisture content 9.1–41.2% (wet basis) on the specific heat of ground and hydrated cowpea were investigated using the method of mixtures. For most of the samples, the specific heat was highest either at 60 °C or 28.6% moisture content. Further increase beyond these levels resulted in a decrease in the specific heat. Density was determined at room temperature. An initial decrease was observed in density of the samples as moisture level increased from 9.1%, but above 23.1% moisture content, the density increased with higher moisture levels. Thermal conductivity was determined by the line probe method. The thermal conductivity of ground and hydrated cowpea was dependent on moisture content and bulk density but independent of temperature.

TECHNOLOGY CHOICE AND TECHNICAL CAPACITY IN GARI PRODUCTION

This study was undertaken to assess the capacity and technology needs of women in Osun and Ondo States for gari production. The field survey was carried out by means of a structured questionnaire, administered through a participatory learning technique. At least two processing centers were visited in each Local Government Area in the two States. Altogether a total of 63 gari processing centers were visited. Mechanical grating of (manually) peeled cassava tubers has been fully adopted, while over 88% of processors have also embraced mechanical dewatering of the grated mash. Manual sieving is still predominant as mechanical sieving devices so far introduced still present problems; Frying also remains a manual operation, though some improved frying devices are being adopted. Women involvement in the operation and management of mechanical devices is not encouraging. Processing centers utilising diesel engine as prime movers predominate (84.7%), but they mostly employ male operators. This study however reveals that given necessary training and sensitisation, women should be able to take on more managerial and operational tasks in agroprocessing ventures. The predominant learning method of apprenticeship needs improvement, while greater attention needs to be paid to environmental issues than presently indicated by the study. Though fatal accidents have not been prevalent, safety consciousness in many of the processing centers leaves much to be desired. To redress some of the inherent problems of current technological practices, a technology profile incorporating the most feasible mechanization option for the unit operations is proposed for gari processing.

Assessment of household kitchen equipment: factors influencing its acquisition and its impact on food consumption in Osun State of Nigeria

Abstract Women in Nigeria are faced with drudgery during food preparation. The acquisition of modern kitchen equipment (MKE) can help in reducing this problem. The study was carried out to investigate the factors influencing the acquisition of household kitchen equipment (KE). Data were collected from users in Ife Central and Ife East Local Government Areas of Osun State using questionnaires as well as interviews and observations. Quantitative analysis was undertaken using the SPSS computer package. The results showed that acquisition of MKE is influenced by socio-economic factors such as age, marital status, income, occupation, educational level and place of residence. The acquisition of MKE was higher among respondents in the age group 31–50 years. Monogamous families have more MKE than polygamous homes. Acquisition of MKE is higher among respondents with tertiary and secondary education. More MKE is also acquired by respondents earning above N4,000.00. Respondents in urban areas possessed more MKE than those in rural areas. The study also revealed that the type of KE acquired affects the food consumption pattern of respondents. Respondents having high- and medium-class KE eat more protein foods and more regularly than others. The policy implications of the results both at domestic and national levels are discussed.