Effect of Drying Method and Variety on Quality of Cassava Starch Extracts

Cassava tubers are main sources of calories and dietary fibre for Nigerians. Cassava tubers are highly perishable and need to be processed immediately after harvest. Cassava can be used for human consumption, livestock feed or industrial purposes. Cassava starch is one of the main industrial products of cassava processing. The long drying times for cassava starch production during sun drying have necessitated the need for alternative drying methods. However, the quality of the starch obtained from these alternative drying methods needs to be investigated. Starch was produced from four different varieties (TME 1, TMS 30572, TMS 01/1235 and TMS 01/1181) of cassava using two drying methods (sun and oven drying at 40oC). The physical (yield and moisture content), functional (water binding capacity, swelling power and solubility) and pasting properties of the starch produced were investigated. The moisture content varied from 9.24 to 10.48%, with oven dried TME 1 having the lowest values and sun dried TMS 01/1181 having the highest value. The yield of starch obtained from drying the four varieties using the two drying methods increased from 458.5 to 687.2g per kg of cassava tuber. The water binding capacity, swelling power and solubility increased from 97.97 to 99.83 g water/g sample, 11.69–14.19 g/ml and 10.20 – 12.96% (g soluble solids/ g DM of whole starch sample) respectively, for the different varieties dried using the two drying methods. Peak viscosity, trough, break down, final viscosity, peak time and pasting temperature values for the four cassava varieties were in the range of 335.76–619.89 RVU, 135.67–192.35 RVU, 199.38–433.99 RVU, 196.01–257.72 RVU, 3.23–3.91 min and 70.05–72.95oC, respectively for the two drying methods. The values obtained from the cassava varieties considered were generally significantly different (except colour) which shows significant effect of cassava variety used on starch properties. Also, cassava starch samples dried at lower temperature have better functional and pasting properties. This indicates that alternative drying methods should be used at temperatures lower than 40oC in order to obtain products of high quality.Key words: Physico-chemical properties, Drying, Cassava, variet

Effect of drying temperatures and pre-treatments on drying characteristics, energy consumption, and quality of bell pepper

Abstract: The effect of air temperature (50°C, 60°C, 70°C, 80°C and 90°C) and pre-treatments (steam, water palm oil-water, groundnut oil-water blanching) on the drying characteristics and quality of bell pepper was investigated.  The results were fitted to six thin-layer drying models and Parabolic model gave the best fit.  The pretreated samples dried faster than untreated samples and had lower values of total energy needed and specific energy requirement.  The ascorbic acid content, color and rehydration index varied from 129.1 to 316.8 mg/100 g dry matter, 0.1 to 0.9, 22 to 33 mL and pretreated dried pepper generally had higher values than untreated samples.   Keywords: modeling, energy consumption, Rehydration index, color, peppe

Effect of Soaking Water Temperature and Time on some Rehydration Characteristics and Nutrient Loss in Dried Bell Pepper

Sun-dried bell pepper was rehydrated at soaking water temperatures of 31°, 37°, 55°, 72° and 90°C, respectively. As the soaking water temperature increased from 31 to 72°C, rehydration ratio and coefficient of rehydration increased from 4.26 to 5.93 and 64.56 to 93.49 respectively while a further increase in soaking temperature to 900C, resulted in a decrease from 5.93 to 4.57 and from 93.49 to 75.77 respectively for the two parameters. At higher soaking water temperatures, larger amounts of vitamin C leached into the soaking water. However for Ca and Fe larger amounts were leached into the soaking water at lower soaking temperatures.

Modeling of hot-air drying of pretreated cassava chips

Tunde-Akintunde T. Y, A. A Afon(Department of Food Science and Engineering, Ladoke Akintola University of Technology, PMB 4000, Ogbomoso, Oyo State, Nigeria)Abstract: Effects of pretreatment (soaking and boiling) on cassava chips dried in a hot air drier at temperature of 60℃ and constant air velocity of 1.5 m/s were investigated.  Mass transfer during air-drying of pretreated cassava chips was described using the Fick’s diffusion model.  Drying took place entirely in the falling rate period.  The form of pretreatment was observed to have an effect on drying rate of the samples.  In order to select a suitable drying model for prediction of the drying kinetics of dried cassava chips, four thin-layer drying models were fitted to the experimental data.  The Page model best described the drying behaviour of pretreated cassava chips with high correlation coefficient values.  The effective moisture diffusivities of the pretreated samples varied from 7.31×10–7 – 8.06×10–7 m2/s.Keywords: modeling, cassava chips, pretreatment, batch dryingCitation: Tunde-Akintunde T. Y, and A. A. Afon. Modeling of hot-air drying of pretreated cassava chips.  Agric Eng Int: CIGR Journal, 2010, 12(2): 34-41.&nbsp

Nutritional and sensory qualities of soymilk kunnu blends

Kunnu, a beverage popular among the Northern Nigerians has a low protein value because it is made from cereals. This may  have a negative effect on the nutritional status of the people who drink it, especially on the growth rate of infants who are given kunnu as a weaning drink. This is because protein is an essential component of the balanced diet required for growth.  Research work carried out on the improvement of the nutritional value of cereals, shows that the fortification of  carbohydrate-rich foods with protein-rich foods improves its nutritious value. As a result of this, a study was carried out to fortify kunnu with soymilk and the effect on its nutritional and sensory properties was evaluated. Kunnu and soymilk were  prepared and it was fortified with soymilk in the ratio 1:1, 2:1, 3:1 and 4:1, and the proximate composition (protein, fat, ash and moisture content), chemical  composition (pH, specific gravity and sedimentation rate) and mineral content (calcium,  magnesium, phosphorus and iron content) were determined. The pH,  protein and mineral content increased as the amount of soymilk added. The pH value ranged from 4.8 to 4.3, while the protein content increased from 2.35 to 2.45%. The calcium and magnesium content also increased from 0.08 to 0.15% and 0.18 to 0.29% respectively. The fat and ash content,  however, decreased respectively from 2.8 to 2.0, and 0.91 to 0.891 with an increase in addition of soymilk. The proximate, chemical and mineral content were significantly different at P < 0.05 while the sensory properties were not significantly different at the same level. The sensory properties (colour, taste, texture, flavor and general acceptability) were, however, observed to decrease with the increase in fortification level of soymilk. The results obtained show that the fortification of  kunnu with  soymilk will result in a more nutritious beverage, but it may have a low level of acceptance with the local populace.Keywords: fortification, kunnu, soymilk, blendsLe Kunnu, une boisson populaire chez les Nigérians du Nord, a une basse valeur en protéines parce qu’il est fabriqué à partir de céréales. Ceci peut avoir un effet  négatif sur l’état nutritionnel des personnes qui le boivent. Il peut avoir un effet négatif surtout sur le taux de croissance des enfants en bas âge à qui l’on donne du kunnu comme boisson de sevrage, étant donné qu’une protéine est une composante essentielle d’un régime alimentaire équilibré requis pour la croissance. Des travaux de recherche menés sur l’amélioration de la valeur nutritive des céréales montrent que la fortification d’aliments riches en  hydrates de carbone par des aliments riches en protéines améliore sa valeur nutritive. Comme résultat de ceci, une étude a été menée en vue de fortifier le kunnu avec du lait de soja et l’effet sur ses propriétés nutritives et sensorielles a été évalué. Le kunnu et le lait de soja ont été préparés et le kunnu a été fortifié avec du lait de soja dans la proportion 1:1, 2:1, 3:1 et  4:1. La composition rapprochée (la teneur en protéines, graisses, cendre et humidité), la composition chimique (pH, gravité spécifique et taux de sédimentation) et la teneur en minéraux (calcium, magnésium, phosphore et fer) ont été déterminées. La teneur en pH, en protéines et en minéraux augmentait au fur et à mesure que la quantité de lait de soja augmentait. La valeur du pH se situait entre 4,8 et 4,3, tandis que la teneur en protéines augmentait de 2,35 à 2,45%. La teneur en calcium et en magnésium a également augmenté de 0,08 à 0,15% et de 0,18 à 0,29%  respectivement. Par contre, les matières grasses et la teneur en cendre ont baissé de 2,8 à 2,0, et de 0,91 à 0,891 avec une augmentation en plus du lait de soja. Les teneurs  rapprochées, en matières chimiques et minérales, étaient très différentes à P < 0,05 tandis que les propriétés sensorielles  n’étaient pas très différentes au  même niveau. Cependant, il a été observé que les propriétés sensorielles (couleur, goût,  texture, saveur et acceptabilité générale) baissent avec l’augmentation du niveau de fortification par du lait de soja. Les  résultats obtenus montrent que la fortification du kunnu par du lait de soja aura comme résultat une boisson plus nutritive,  mais qui peut avoir un niveau insuffisant d’acceptation auprès de la population locale. Mots-clés: fortification, kunnu, lait de soja, mélanges 

Study on Drying Kinetics of Fermented Corn Grains

Corn grains were fermented for three days and later drained and dried at 600C, 650C and 700C in a convective hot air dryer. Kinetics of drying was investigated using Fick’s second law. Drying pattern was observed to be in the falling rate period. Non linear regression analysis software (SPSS), was used to fit in the experimental data and the coefficient of determination was found to be greater than 0.90 for all the models except Midilli. The values of R2, RMSE, MBE and reduced chi square showed that Logarithm model best described the drying behaviour of the samples. Keyword: fermented corn, hot air drying, mathematical modeling, laboratory tunnel drye

Effect of drying conditions on energy utilization during cocoyam drying

Cocoyam samples soaked in sodium metabisulphite (SM) and water blanched (WB) were oven dried at 50, 60 and 70° C and microwave power levels of 385, 540 and 700 W while untreated samples were sun dried. The effect of drying on selected properties of cocoyam was studied. The drying time generally reduced with increase in drying temperature and power level used. The use of SM pretreatment resulted in lower drying times compared with WB pretreatment. Effective moisture diffusivity values (Deff) for all the drying conditions varied from 5.27 x 10-8 to 2.07 x 10-6 m2/s and SM samples had higher values than WB samples.  Activation energy values for oven drying were 37.41 KJ/mol and 61.79 KJ/mol and that for microwave drying were 38.59 and 41.91W/g for SM and WB samples respectively.  The energy consumption varied from 125.1 to 142.8 kWh and 308 to 396.7 Wh while that of specific energy requirement varied from 86.2 to 106.5 kWh/kg and 1.49 to 2.03 KJ/kg water for oven drying and microwave drying respectively

Modelling the Water Absorption Characteristics of Different Maize (Zea Mays L.) Types during Soaking

Water absorption characteristic of six different types of maize namely; dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn during water soaking were studied at four different temperatures of 30, 40, 50 and 60 o C.The water absorption data fitted very well into both Peleg’s and Becker's models as to correspondingly determine the saturation moisture content (hydration equilibrium moisture content) and moisture diffusivity. The water absorption capacity and saturation moisture contents of each maize type increased as the water soaking temperature increased. The absorption kinetics followed the Fick's law of diffusion during the first hours of soaking. The determined diffusion coefficients values varied from 10.6 to 13.5 × 10-11 m2/s for sweet corn, 6.74 to 8.88 × 10-11 m2/s for white flour, 5.27 to 7.09 × 10-11 m2/s for yellow flour, 4.44 to 5.79× 10-11 m2/s for popcorn, 4.25 to 5.69 × 10-11 m2/s for dent white corn and 3.28 to 4.68 × 10-11 m2/s for dent yellow corn, respectively. An Arrhenius–type equation was used to relate the moisture diffusivity (diffusion coefficient) of dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn to temperature, and the energy of activation for dent corn (white and yellow), corn flour (white and yellow), popcorn and sweet corn was estimated. The values determined were 8.17, 9.59, 7.83, 8.45, 6.61 and 8.01 kJ/mol for dent white corn, dent yellow corn, white corn flour, yellow corn flour, sweet corn and popcorn, respectively. Keywords: Maize varieties; Water absorption; Peleg’s model; Becker’s model; Arrhenius-type equatio

DEVELOPMENT OF A TRAY DRYER FOR FRUITS AND VEGETABLES USING ZIG-ZAG AIR FLOW CONFIGURATION

 Post harvest losses in fruits and vegetables in developing countries like Nigeria is high due to poor storage and processing facilities. The use of cabinet dryer for dehydration of fruits and vegetables to improve their shelf life has a drawback of non-uniformity in drying along the length of trays. Hence an effort was made to solve this problem by using a zigzag air flow pattern configuration. A cabinet dryer of capacity21kg/batch was designed and developed. The dryer was tested with okra slices using zigzag air flow pattern configuration. At an air flow rate of 8.8m3/s and 600c it took about 9 hours to reduce the moisture content from 79.55% (w.b) to 6.03%(w.b). Results obtained showed that drying of the okra slices took place in the falling rate period. The drying efficiency of the dryer was found to be 70%