Influence of Blanching on the Drying Characteristics of Convective Hot Air Dried Aerial Yam (original) (raw)
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Effect of Drying and Blanching Parameters on Drying Rate of 'Poundo' Yam
2013
This study was carried out to determine the effects of drying and blanching parameters on drying rate of 'poundo' yam. The 'poundo' yam was produced from white yam (Dioscorea rotundata) using an electrically powered experimental dryer. The product was dried to an average moisture content of 12 % w.b. The moisture loss and the drying rate were determined. The drying rate was subjected to statistical analysis using 3 x 3 x 3 factorial design to study the effects of drying temperatures (55 o C, 60 o C and 65 o C), blanching temperatures (80 o C, 90 o C and 100 o C), and blanching durations (10 minutes, 20 minutes and 30 minutes) on drying rate. It was observed that the drying temperature, blanching temperature, blanching duration and interaction between the three factors had significant effect on the drying rate at 5 % level of confidence. It is therefore established that increase in drying temperature irrespective of pre-treatment methods leads to decrease in drying time.
The effects of SSB (superheated steam blanching) time (0, 3, 6, 9 and 12 min) and drying temperature (50, 60, 70 and 80C) on drying kinetics and quality of yam slices under air impingement drying were investigated in this paper. Results indicated that the positive effect of SSB on drying rate might be overshowed by the negative effect of starch gelatinization and appropriate SSB could accelerate drying rate, whereas the effect of excessive SSB is reversed. The moisture effective diffusivity ranged from 1.1540 ¥ 10 -9 to 2.8431 ¥ 10 -9 m 2 /s, calculated using Fick's second law of diffusion. The activation energy determined from the slope of the Arrhenius plot, ln(D eff ) versus 1/(T + 273.15), was 20.925 kJ/mol. Moderate increase in SSB time or decrease in drying temperature can improve the whiteness index of dried yam slices, whereas increase in SSB time and drying temperature can decrease the rehydration ratio of dried yam slices.
Convective hot air drying of blanched yam slices
International Journal of Food Science & Technology, 2008
In this study, a laboratory convective hot air dryer was used for the thin layer drying of blanched yam slices and experimental moisture ratio was compared with Newton, Logarithmic, Henderson and Pabis, modified Henderson and Pabis, approximation of diffusion, modified page 1, two-term exponential, Verma et al. and Wang and Singh models. Among all the models, the approximation of diffusion model was found to satisfactorily describe the kinetics of air-drying of blanched yam slices. The increase in air temperature significantly reduced the drying time with no constant rate period but drying occurs in falling rate period. The effective diffusivity values varied between 7.62 • 10)8 to 9.06 • 10)8 m 2 s)1 and increased with increase in temperature. An Arrhenius relation with an activation energy value of 8.831 kJ mol)1 showed the effect of temperature on moisture diffusivity.
Effect of boiling, thickness (0.5 and 1cm) and temperature on drying time of Dioscorea bulbifera was investigated in a fabricated hot air drier at a temperature range of 50 -70°C. . The drying process was conducted in triplicates and average values recorded. The average moisture ratio was used to plot the drying characteristics curves for the temperature range studied with dimensionless moisture ratio against drying time. Drying took place mainly in the falling rate period whiles increased slab thickness influenced drying time for both the boiled and fresh yam slabs at all temperatures. Boiling was shown to have led to a decrease in the rate of moisture movement which led to increase in drying time of the yam slice at both thickness (0.5, 1cm). Drying time subsequently reduced with increase in hot air temperature. 70°C is therefore recommended for drying aerial yam. These results will provide food processors with information to determine the best processing conditions for the dioscorea bulbifera which will finally lead to elimination of waste.
Effect of Temperature, Drying time and Thickness of Sliced Yam on Weight Loss of Yam during Drying
Drying is one of the most effective post harvest operations being carried out on agricultural products especially on tubers to preserve its shelf life. In this research, drying process in yam was investigated using drying temperature, time of drying and the thickness of the sliced tuber. The Response Surface Methodology (RSM) was employed to analyzed the result of the investigation. Empirical results shows that the linear effect of thickness of sliced tubers, and the interaction of temperature and time of drying had significant effect on weight loss of the sliced tubers at p 0.05. Furthermore, the quadratic effect on the drying time and temperature had significant effect on weight loss. The three factors manipulated during the drying process accounted for 94.2% of the variations observed in the final weight loss of the dried chips.
Effects of Pre-Treatment on Drying Rate and Protein Content of Yam Slices
An experiment to evaluate the drying rate of pretreated yam slices at varying temperatures was conducted at the Federal University of Technology, Akure. The yam slices were subjected to blanching by soaking in hot water at temperatures of 80 0 C, 90 0 C and 100 0 C for 10 minutes and later dried in a cabinet type dryer fitted with an electric heater. The drying process was done at three levels of temperatures (100 0 C, 110 0 C, 120 0 C) and time (4hrs, 5hrs and 6hrs). The experimental results show that the blanching temperature have significant effect on both the drying rate and protein content at 5 level of significance It was also observed from the result of the analysis that samples blanched at 80 0 C had the highest rate of water loss and protein content when compared to other treatments. The least values of drying rate was obtained at the 90 0 C blanching temperature. INTRODUCTION Yams (Dioscorea spp.) are major carbohydrate sources for most people in the West and Central Afri...
Air Drying Characteristics of Aerial Yam ( Dioscorea bulbifera )
The study investigated the air drying characteristics of aerial yam in a fabricated air dryer within a temperature range of 50 to 70°C. Prior to drying, the sample was divided into two portions; one part was boiled at 100°C for 20min and the other part left fresh. The drying data was fitted to twelve well-known thin layer drying models. Among the models used, the Midilli et al.,Verma et al., Diffusion Approach, Wang and Singh, Parabolic and Simplified Fick's Diffusion models were found to be the best models to predict the moisture ratio values during the drying process with high capability. The effective moisture diffusivity was found to vary between the range of 1.401 ×10-10 m 2 /s to 6.720 x 10-10 m 2 /s for the fresh yam slabs and 7.223 x 10-11 m 2 /s and 2.306 x 10-10 m 2 /s for the boiled yam slabs over the temperature range of 50 to 70°C. The values for activation energy were 28.42kJ/mol, 30.33kJ/mol for fresh yam samples of thicknesses of 0.5cm and 1cm respectively, whereas the values for boiled yam were 6.77kJ/mol and 15.37kJ/mol for slabs of 1cm and 0.5cm thicknesses respectively. Pre-treating the aerial yam by boiling will be beneficial in the optimisation of processing method for the Dioscorea bulbifera.
Thin-layer drying kinetics of yam slices, physicochemical, and functional attributes of yam flour
Journal of Food Process Engineering, 2020
This study aimed to investigate the effect of temperature (50-80 C) on the drying behavior of yam slices and to evaluate the physicochemical and functional properties of yam flour. The results revealed that higher temperature enhanced the drying rate and moisture diffusivity (2.01 × 10 −10-4.25 × 10 −10 m 2 s −1) and the drying process occurred entirely in the falling rate period. Twelve thin-layer drying models were employed to fit the drying data using statistical parameters; coefficient of determination (R 2), root mean square error, chi-square (χ 2), sum of squares residual, and mean bias error. The results suggested that logarithmic for 50 C (R 2 =0 .9990) and parabolic for 60-80 C (R 2 =0 .9977-0.9991) were the best models that can adequately explain the drying behavior of yam slices. Different physicochemical and functional properties of yam flour were significantly affected by the drying temperatures. However, the developed yam flour exhibited a satisfactory range of nutritional contents, such as protein (4.79-5.97%), fat (0.59-0.74%), ash (5.57-6.60%), fiber (0.83-1.96%), starch (65.59-73.93%), carbohydrate (85.69-87.53%), and total phenolics (10.68-11.88 mg Gallic Acid Equivalent/100 g (GAE/100 g). Therefore, the drying kinetic results and the physicochemical quality of developed yam flour could be useful for its industrial production. Practical Applications: Yam is one of the leading root crops in the world and used as staple food in many countries. Postharvest storage and transport of the raw yam are one of the main problems in developing countries. The objective of this study was to investigate the effect of drying temperature on the thin-layer drying kinetics of yam slices and to evaluate a suitable drying model for describing the drying process together with the food compositions, total phenolics, and other functional and color characteristics. This study revealed a useful outcome that could convince the food producers for industrial production and consumers to consider the yam flour as a suitable alternative to rice, wheat, or corn flour for the formulation of high-quality health food products, such as bakery, confectionery, snack, noodle, soup, and other products.
Air drying characteristics of Aerial yam (Dioscorea bubifera)
The study investigated the air drying characteristics of aerial yam in a fabricated air dryer within a temperature range of 50 to 70°C. Prior to drying, the sample was divided into two portions; one part was boiled at 100°C for 20min and the other part left fresh. The drying data was fitted to twelve well-known thin layer drying models. Among the models used, the Midilli et al., Verma et al., Diffusion Approach, Wang and Singh, Parabolic and Simplified Fick’s Diffusion models were found to be the best models to predict the moisture ratio values during the drying process with high capability. The effective moisture diffusivity was found to vary between the range of 1.401 ×10-10 m2/s to 6.720 x 10-10 m2/s for the fresh yam slabs and 7.223 x 10-11 m2/s and 2.306 x 10-10 m2/s for the boiled yam slabs over the temperature range of 50 to 70°C. The values for activation energy were 28.42kJ/mol, 30.33kJ/mol for fresh yam samples of thicknesses of 0.5cm and 1cm respectively, whereas the values for boiled yam were 6.77kJ/mol and 15.37kJ/mol for slabs of 1cm and 0.5cm thicknesses respectively. Pre-treating the aerial yam by boiling will be beneficial in the optimisation of processing method for the D.bulbifera.
Single-Layer Drying of Purple Yam (Dioscoreaalata L.) Slices
Bulgarian Journal of Agricultural Science, 2018
Muhidong, J., S. Salengke and A. Surestyana, 2018. Single-layer drying of purple yam (Dioscoreaalata L.) slices. Bulg. J. Agric. Sci., 24 (1): 145–150 This research was intended to fi nd the best fi tted model to represent the drying behaviors of purple yam slices during singlelayer drying process. The research was conducted at Food Processing Laboratory of Agricultural Engineering Department, Hasanuddin University – Indonesia. Two levels of drying temperature (40 and 50°C) under two different air velocities (1.0 and 2.0 m.s-1) were applied. A tray dryer (Model EH-TD-300 Eunha Fluid Science) was utilized as the main equipment. The moisture ratios resulted from each drying treatment combination was determined and nine different thin-layer models were fi tted to these moisture ratios. The results indicated that all models performed well as shown by their high R2 values (> 0.9) with small χ2 and RMSE values. However, among all models, the Midili-Kucuk model consistently showed the b...