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Papers by Emmanuel Amankwah

Thin-layer modeling of FHIA-21 (Tetraploid Plantain) slices was studied in a conventional hot-air... more Thin-layer modeling of FHIA-21 (Tetraploid Plantain) slices was studied in a conventional hot-air dryer. The samples were dried at 50, 60, 70 and 80°C air temperature with control and blanching as pretreatments. Increase in drying air temperature from 50 to 80°C decreased the drying time from 16 and 17.5 hours to 3 and 7 hours for untreated and blanched samples, respectively. Drying of the plantain occurred in falling rate period. Five thin layer drying models were evaluated by fitting to the experimental moisture ratio data. Among the mathematical models investigated, the Page model satisfactorily described the drying behaviour of the slices with high r 2 values and low χ 2 and RMSE. The effective moisture diffusivity of the plantain slices increased as the drying air temperature was increased. Also the moisture diffusivity and activation energy were lower for blanched samples.

International Journal of Food Engineering, 2018

Crank’s analytical approximations for Fick’s diffusion equation were used to investigate the effe... more Crank’s analytical approximations for Fick’s diffusion equation were used to investigate the effect of moisture dependent sample thickness and diffusivity on the behavior of yam (Dioscoreaceae rotundata) cubicles during drying processes. Drying and shrinkage experiments were separately conducted at temperatures of 30, 40 and 50 °C in a cabinet drier. The comparative study of moisture dependent shrinkage and moisture dependent diffusivity justifies the interdependence of diffusivity and shrinkage due to water loss during drying. The behavior for yam is best explained by a combination of fractal moisture dependent shrinkage and moisture dependent diffusion, describing both the drying and rate curves better with good prediction of the high moisture regions. This assertion was reached as a result of low mean square error, standard error, percentage relative deviation, Akaike’s Information Criterion and high coefficient of determination. The results may indicate a varying mobility of wat...

GSTF Journal on Agricultural Engineering, 2014

Drying characteristics of banana slices were determined for 4, 6 and 8mm thickness in a conventio... more Drying characteristics of banana slices were determined for 4, 6 and 8mm thickness in a conventional oven dryer at temperatures between 50-70 °C. Six empirical models were used for fitting the experimental drying curve. The influence of banana thickness and temperature on the moisture diffusivity and drying rate were investigated. Temperature strongly affected moisture diffusivity and drying rate. Drying rate increased with decreased thickness while moisture diffusivity dropped at higher banana slice thickness. The Lewis model fitted well the experimental data.

Food Science and Quality Management, 2013

The study was conducted to formulate and optimize a consumer acceptable fresh Moringa leaves (ext... more The study was conducted to formulate and optimize a consumer acceptable fresh Moringa leaves (extract) beverage. A constrained three component mixture design consisting of fresh tender Moringa leaves extract, pineapple juice and carrot extract was used to optimize the formulation of the beverage based on sensory acceptability (color, taste, flavor, aftertaste and overall acceptability). A constant amount of ginger root distillate was used to improve the flavor of the beverage. The optimum component proportions consisting of 50-52% Moringa extract, 38-40% Pineapple juice and 10-12% Carrot extract was validated to be adequate and acceptable to consumers. The findings show that fresh Moringa leaves could be processed into acceptable beverage, to extend its beneficial and nutraceutical properties to many consumers.

Food Science and Quality Management, 2013

To determine the nutritional composition of fresh Moringa leaf beverage (50% moringa extract, 38%... more To determine the nutritional composition of fresh Moringa leaf beverage (50% moringa extract, 38% pineapple juice and 12% carrot extract) and assess the keeping quality. Proximate analysis, chemical analysis and shelf stability studies under three different storage conditions of temperature were conducted on the beverage. Fresh Moringa oleifera beverage recorded 2.9g/100ml of protein, 1.02mg of iron and 159.14mg/100ml of vitamins C. After 8weeks of storage 78% of vitamins C was still retained even under the most severe storage condition (sunlight). There was no microbial growth under all the conditions of storage, and the product was still acceptable. Fresh Moringa oleifera beverage is therefore an excellent means of distributing nutrients to the malnourished and other consumers.

The experimental equilibrium moisture content of yam (Dioscorea rotundata; cultivar: Dente) at te... more The experimental equilibrium moisture content of yam (Dioscorea rotundata; cultivar: Dente) at temperatures of 25°C and 50°C were determined at relative humidity from 0% to 95% employing the dynamic vapor sorption analyzer. Wet yam samples with about 68% initial moisture content were used, first for desorption and subsequently for sorption. Water activity decreased with increased temperature at constant equilibrium moisture content. The desorption and adsorption isotherms were fitted by the Guggenheim-Anderson-de Boer (GAB), Henderson, Halsey, Oswin, Smith, Brunauer-Emmett-Teller (BET) and Peleg models. On the basis of the fit the Peleg, GAB and Oswin models were most suitable for describing the observed data. When the focus is on drying, the GAB (3 parameters) and empirical Peleg model (4 parameters) performed best. Of these, GAB is preferable because it has fewer parameters, which, moreover, have a physical meaning. .

African Journal of Food Science, Oct 31, 2013

The proximate nutrients, calorific value, mineral nutrients and lipid characteristics of the seed... more The proximate nutrients, calorific value, mineral nutrients and lipid characteristics of the seed pastes of four (4) peanut (Arachis hypogaea) varieties namely: Sinkarzie, F-mix, JL 24 and Manipintar were investigated. Crude protein values ranged between 23.62% (±0.34) in Sinkarzie to 28.88% (±0.24) in JL 24. Crude fat ranged between 38.11% (±0.47) in JL 24 to 48.79% (±0.20) in Sinkarzie. Carbohydrate content ranged between 11.54% (±0.18) for Sinkarzie to 19.65% (±0.55) in JL 24. The energy content in kCal/100 g sample ranged between 537.06 in JL 24 to 581.54 in Manipintar. Calcium contents (mg/100 g) ranged between 23.14 (±0.49) in Manipintar to 128.25 (±2.90) in F-mix. At room temperature (25°C), all the oils from the four groundnut varieties were pale yellow coloured liquids with nutty odour. Saponification value (mg KOH/g oil) ranged from 144.70 (±0.63) in JL 24 to 208.97 (±0.58) in Sinkarzie. Iodine value (mg/100 g) ranged from 79.10 (±0.15) in Sinkarzie to 86.93 (±0.26) in F-mix. Percentage free fatty acids (% FFA) ranged from 8.09% (±0.20) in Manipintar to 14.21% (±0.10) in F-mix. The results indicate that while the groundnut seeds could be used in fighting malnutrition, the oils obtained from the seeds could also be used for domestic and industrial purposes.

Journal of the Ghana Science Association, 2006

Agricultural Engineering International: The CIGR Journal, 2018

The experimental equilibrium moisture content of yam ( Dioscorea rotundata; cultivar: Dente ) at ... more The experimental equilibrium moisture content of yam ( Dioscorea rotundata; cultivar: Dente ) at temperatures of 25 and 50°C were determined at relative humidities from 0 to 95% employing the Dynamic Vapour Sorption analyzer. Wet yam samples with about 68% initial moisture content were used, first for desorption and subsequently for sorption. Water activity decreased with increased temperature at constant equilibrium moisture content. The desorption and adsorption isotherms were fitted by the GAB, Henderson, Halsey, Oswin, Smith, BET and Peleg models. On the basis of the fit the Peleg, GAB and Oswin models were most suitable for describing the observed data. When the focus is on drying, the GAB (3 parameters) and empirical Peleg model (4 parameters) performed best. Of these, GAB is preferable because it has fewer parameters, which, moreover, have a physical meaning.

Applied Sciences, 2019

This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (... more This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (SAD) compared to solar drying (SD) and open sun drying (OSD). The evaluation concerns the drying cycle for batches of yam, the effect on vitamin C, color and composition. As SAD can be applied during the night, by using air dehumidified by passing through a bed of silica gel, the cycle time for drying batches of yam can be reduced over 20–25% compared to SD and halved compared to OSD. SAD is thereby most effective during the first nights of drying when the driving force is the highest. Composition was not affected by drying methods but did affect vitamin C content. Vitamin C retention is not significant different for SD and SAD, but with a slight preference for SD. For three yam cultivars (‘Pona’, ‘Lilii’ and ‘Dente’), ‘Lilii’ dried fastest and ‘Dente’ drying slowest. SAD maintained 16 the whitish color of yam better than the other drying methods.

Drying Technology, 2017

Coupled partial differential equations were developed to investigate which collector lengths are ... more Coupled partial differential equations were developed to investigate which collector lengths are appropriate for drying and adsorbent regeneration under prevailing Ghanaian weather. Unlike approaches based on empirical data, the numerical model is more flexible. Effects of operational and design variables on outlet temperature and performance were systematically studied. Collector length and air speed affect performance indicators. Operational overall heat loss coefficient, an important characteristic of the collector, is not constant but varies during the day. With plausible physical parameters, the model describes the experimental data well. Collector lengths of 1.5 and 4.5 m suited drying and regeneration, respectively.

American Journal of Food Technology, 2011

Thin-layer modeling of FHIA-21 (Tetraploid Plantain) slices was studied in a conventional hot-air... more Thin-layer modeling of FHIA-21 (Tetraploid Plantain) slices was studied in a conventional hot-air dryer. The samples were dried at 50, 60, 70 and 80°C air temperature with control and blanching as pretreatments. Increase in drying air temperature from 50 to 80°C decreased the drying time from 16 and 17.5 hours to 3 and 7 hours for untreated and blanched samples, respectively. Drying of the plantain occurred in falling rate period. Five thin layer drying models were evaluated by fitting to the experimental moisture ratio data. Among the mathematical models investigated, the Page model satisfactorily described the drying behaviour of the slices with high r 2 values and low χ 2 and RMSE. The effective moisture diffusivity of the plantain slices increased as the drying air temperature was increased. Also the moisture diffusivity and activation energy were lower for blanched samples.

International Journal of Food Engineering, 2018

Crank’s analytical approximations for Fick’s diffusion equation were used to investigate the effe... more Crank’s analytical approximations for Fick’s diffusion equation were used to investigate the effect of moisture dependent sample thickness and diffusivity on the behavior of yam (Dioscoreaceae rotundata) cubicles during drying processes. Drying and shrinkage experiments were separately conducted at temperatures of 30, 40 and 50 °C in a cabinet drier. The comparative study of moisture dependent shrinkage and moisture dependent diffusivity justifies the interdependence of diffusivity and shrinkage due to water loss during drying. The behavior for yam is best explained by a combination of fractal moisture dependent shrinkage and moisture dependent diffusion, describing both the drying and rate curves better with good prediction of the high moisture regions. This assertion was reached as a result of low mean square error, standard error, percentage relative deviation, Akaike’s Information Criterion and high coefficient of determination. The results may indicate a varying mobility of wat...

GSTF Journal on Agricultural Engineering, 2014

Drying characteristics of banana slices were determined for 4, 6 and 8mm thickness in a conventio... more Drying characteristics of banana slices were determined for 4, 6 and 8mm thickness in a conventional oven dryer at temperatures between 50-70 °C. Six empirical models were used for fitting the experimental drying curve. The influence of banana thickness and temperature on the moisture diffusivity and drying rate were investigated. Temperature strongly affected moisture diffusivity and drying rate. Drying rate increased with decreased thickness while moisture diffusivity dropped at higher banana slice thickness. The Lewis model fitted well the experimental data.

Food Science and Quality Management, 2013

The study was conducted to formulate and optimize a consumer acceptable fresh Moringa leaves (ext... more The study was conducted to formulate and optimize a consumer acceptable fresh Moringa leaves (extract) beverage. A constrained three component mixture design consisting of fresh tender Moringa leaves extract, pineapple juice and carrot extract was used to optimize the formulation of the beverage based on sensory acceptability (color, taste, flavor, aftertaste and overall acceptability). A constant amount of ginger root distillate was used to improve the flavor of the beverage. The optimum component proportions consisting of 50-52% Moringa extract, 38-40% Pineapple juice and 10-12% Carrot extract was validated to be adequate and acceptable to consumers. The findings show that fresh Moringa leaves could be processed into acceptable beverage, to extend its beneficial and nutraceutical properties to many consumers.

Food Science and Quality Management, 2013

To determine the nutritional composition of fresh Moringa leaf beverage (50% moringa extract, 38%... more To determine the nutritional composition of fresh Moringa leaf beverage (50% moringa extract, 38% pineapple juice and 12% carrot extract) and assess the keeping quality. Proximate analysis, chemical analysis and shelf stability studies under three different storage conditions of temperature were conducted on the beverage. Fresh Moringa oleifera beverage recorded 2.9g/100ml of protein, 1.02mg of iron and 159.14mg/100ml of vitamins C. After 8weeks of storage 78% of vitamins C was still retained even under the most severe storage condition (sunlight). There was no microbial growth under all the conditions of storage, and the product was still acceptable. Fresh Moringa oleifera beverage is therefore an excellent means of distributing nutrients to the malnourished and other consumers.

The experimental equilibrium moisture content of yam (Dioscorea rotundata; cultivar: Dente) at te... more The experimental equilibrium moisture content of yam (Dioscorea rotundata; cultivar: Dente) at temperatures of 25°C and 50°C were determined at relative humidity from 0% to 95% employing the dynamic vapor sorption analyzer. Wet yam samples with about 68% initial moisture content were used, first for desorption and subsequently for sorption. Water activity decreased with increased temperature at constant equilibrium moisture content. The desorption and adsorption isotherms were fitted by the Guggenheim-Anderson-de Boer (GAB), Henderson, Halsey, Oswin, Smith, Brunauer-Emmett-Teller (BET) and Peleg models. On the basis of the fit the Peleg, GAB and Oswin models were most suitable for describing the observed data. When the focus is on drying, the GAB (3 parameters) and empirical Peleg model (4 parameters) performed best. Of these, GAB is preferable because it has fewer parameters, which, moreover, have a physical meaning. .

African Journal of Food Science, Oct 31, 2013

The proximate nutrients, calorific value, mineral nutrients and lipid characteristics of the seed... more The proximate nutrients, calorific value, mineral nutrients and lipid characteristics of the seed pastes of four (4) peanut (Arachis hypogaea) varieties namely: Sinkarzie, F-mix, JL 24 and Manipintar were investigated. Crude protein values ranged between 23.62% (±0.34) in Sinkarzie to 28.88% (±0.24) in JL 24. Crude fat ranged between 38.11% (±0.47) in JL 24 to 48.79% (±0.20) in Sinkarzie. Carbohydrate content ranged between 11.54% (±0.18) for Sinkarzie to 19.65% (±0.55) in JL 24. The energy content in kCal/100 g sample ranged between 537.06 in JL 24 to 581.54 in Manipintar. Calcium contents (mg/100 g) ranged between 23.14 (±0.49) in Manipintar to 128.25 (±2.90) in F-mix. At room temperature (25°C), all the oils from the four groundnut varieties were pale yellow coloured liquids with nutty odour. Saponification value (mg KOH/g oil) ranged from 144.70 (±0.63) in JL 24 to 208.97 (±0.58) in Sinkarzie. Iodine value (mg/100 g) ranged from 79.10 (±0.15) in Sinkarzie to 86.93 (±0.26) in F-mix. Percentage free fatty acids (% FFA) ranged from 8.09% (±0.20) in Manipintar to 14.21% (±0.10) in F-mix. The results indicate that while the groundnut seeds could be used in fighting malnutrition, the oils obtained from the seeds could also be used for domestic and industrial purposes.

Journal of the Ghana Science Association, 2006

Agricultural Engineering International: The CIGR Journal, 2018

The experimental equilibrium moisture content of yam ( Dioscorea rotundata; cultivar: Dente ) at ... more The experimental equilibrium moisture content of yam ( Dioscorea rotundata; cultivar: Dente ) at temperatures of 25 and 50°C were determined at relative humidities from 0 to 95% employing the Dynamic Vapour Sorption analyzer. Wet yam samples with about 68% initial moisture content were used, first for desorption and subsequently for sorption. Water activity decreased with increased temperature at constant equilibrium moisture content. The desorption and adsorption isotherms were fitted by the GAB, Henderson, Halsey, Oswin, Smith, BET and Peleg models. On the basis of the fit the Peleg, GAB and Oswin models were most suitable for describing the observed data. When the focus is on drying, the GAB (3 parameters) and empirical Peleg model (4 parameters) performed best. Of these, GAB is preferable because it has fewer parameters, which, moreover, have a physical meaning.

Applied Sciences, 2019

This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (... more This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (SAD) compared to solar drying (SD) and open sun drying (OSD). The evaluation concerns the drying cycle for batches of yam, the effect on vitamin C, color and composition. As SAD can be applied during the night, by using air dehumidified by passing through a bed of silica gel, the cycle time for drying batches of yam can be reduced over 20–25% compared to SD and halved compared to OSD. SAD is thereby most effective during the first nights of drying when the driving force is the highest. Composition was not affected by drying methods but did affect vitamin C content. Vitamin C retention is not significant different for SD and SAD, but with a slight preference for SD. For three yam cultivars (‘Pona’, ‘Lilii’ and ‘Dente’), ‘Lilii’ dried fastest and ‘Dente’ drying slowest. SAD maintained 16 the whitish color of yam better than the other drying methods.

Drying Technology, 2017

Coupled partial differential equations were developed to investigate which collector lengths are ... more Coupled partial differential equations were developed to investigate which collector lengths are appropriate for drying and adsorbent regeneration under prevailing Ghanaian weather. Unlike approaches based on empirical data, the numerical model is more flexible. Effects of operational and design variables on outlet temperature and performance were systematically studied. Collector length and air speed affect performance indicators. Operational overall heat loss coefficient, an important characteristic of the collector, is not constant but varies during the day. With plausible physical parameters, the model describes the experimental data well. Collector lengths of 1.5 and 4.5 m suited drying and regeneration, respectively.

American Journal of Food Technology, 2011