Drying Of Potato Research Articles

Modeling of Time Dependent Variation of Moisture Content, Density, Porosity and Specific Volume during Drying of Apple and Potato

Modeling of Time Dependent Variation of Moisture Content, Density, Porosity and Specific Volume during Drying of Apple and Potato In this work, drying experiments were conducted for one variety of apple (Fuji) and three varieties of potato, namely, Kufri Chipsona-1, Kufri Himsona and Kufri Bahar at temperature 60, 70 and 80ºC in the tray dryer. The effect of temperature on drying characteristics and quality parameters of the dried apple and potato slices was determined. For investigating the drying characteristics of apple and potato, an appropriate drying model was presented by modifying existing drying model. A non-linear regression procedure was employed to fit several drying models available in the literature to the experimental data. The models were compared according to chi-square ( χ 2 ), coefficient of determination ( R2 ) and root mean square error (RMSE). Results based on our model had close resemblance with experimental observations. Drying constant was correlated with temperature by using exponential equation.

Local root abscisic acid (ABA) accumulation depends on the spatial distribution of soil moisture in potato: implications for ABA signalling under heterogeneous soil drying.

Patterns of root abscisic acid (ABA) accumulation ([ABA]root), root water potential (Ψroot), and root water uptake (RWU), and their impact on xylem sap ABA concentration ([X-ABA]) were measured under vertical partial root-zone drying (VPRD, upper compartment dry, lower compartment wet) and horizontal partial root-zone drying (HPRD, two lateral compartments: one dry, the other wet) of potato (Solanum tuberosum L.). When water was withheld from the dry compartment for 0-10 d, RWU and Ψroot were similarly lower in the dry compartment when soil volumetric water content dropped below 0.22cm(3) cm(-3) for both spatial distributions of soil moisture. However, [ABA]root increased in response to decreasing Ψroot in the dry compartment only for HPRD, resulting in much higher ABA accumulation than in VPRD. The position of the sampled roots (~4cm closer to the surface in the dry compartment of VPRD than in HPRD) might account for this difference, since older (upper) roots may accumulate less ABA in response to decreased Ψroot than younger (deeper) roots. This would explain differences in root ABA accumulation patterns under vertical and horizontal soil moisture gradients reported in the literature. In our experiment, these differences in root ABA accumulation did not influence [X-ABA], since the RWU fraction (and thus ABA export to shoots) from the dry compartment dramatically decreased simultaneously with any increase in [ABA]root. Thus, HPRD might better trigger a long-distance ABA signal than VPRD under conditions allowing simultaneous high [ABA]root and relatively high RWU fraction.

Comparison of Three Blanching Treatments on the Color and Anthocyanin Level of the Microwave-Assisted Spouted Bed Drying of Purple Flesh Sweet Potato

Browning and a serious drop in anthocyanin level occur during microwave-assisted spouted bed drying (MWSB) of purple-flesh sweet potato (PFSP) cubes. Blanching pretreatment inhibits browning and also affects the drying behavior. Effects of microwave blanching (MWB), hot water blanching (HWB), and steam blanching (SB) were examined experimentally. The results showed that MWB leads to rapid peroxidase (POD) degradation, reduces the drying time, and yields highest anthocyanin level after MWSB drying. However, the color of the dried product was not as bright and purple as those obtained by HWB and SB treatments. Microwave blanching can improve the MWSB drying process to maintain the anthocyanin level in dried products while reducing the drying time.

Characterization of Thin Layer Hot Air Drying of Sweet Potatoes (I pomoea batatas L.) Slices

The effect of drying temperature (50, 60, 70 and 90C) and sample thickness (0.3, 0.4, 0.6 and 0.8 cm) on characterization of hot air drying of sweet potato slices were investigated. Results indicated that drying took place in the falling rate period. The average values of effective moisture diffusivities of sweet potato slices ranged from 3.66 × 10−10 to 2.11 × 10−9 m2/s within the given drying temperature range. The average activation energy values were 13.48–16.50 kJ/mol for sample thickness of 0.3–0.8 cm. Twelve thin layer drying models were fitted using experimental drying data. The goodness of fit for models was evaluated using the values of coefficient of determination (R2), root mean square error, chi-square (χ2) and mean relative percent deviation (P). Results showed that fitting accuracy of Hii et al. model was better than other models. Practical Applications Sweet potato (Ipomoea batatas L.) is widely grown in many countries. In developing countries, there are many problems related to storage and transport of the raw sweet potatoes. The objective of this study was to investigate the effect of drying temperature and sample thickness conditions on the thin layer drying of sweet potato, and to evaluate a suitable drying model for describing the drying process. In addition, the effective moisture diffusivity and Ea in the drying process of sweet potato slices were calculated.

Shrinkage and porosity effects on heat and mass transfer during potato drying

Fruits and vegetables are porous in nature and undergo pronounced shrinkage during convective drying process. Therefore, shrinkage and porosity should be taken into consideration while predicting heat and mass transfer. This work was conducted to study shrinkage and porosity changes along with simultaneous heat and mass transport during the process. Potato slices were subjected to drying for 7h at 62°C. It was observed that shrinkage varies linearly with respect to moisture content and reduction in radial dimension of potato slices was around 35%. Porosity undergoes rapid increase after attaining certain moisture content in final stages of drying. The work was extended to study the influence of shrinkage and porosity on heat and mass transfer. Simulated results were validated with experimental values. This model can be employed to predict temperature, moisture, density profiles and to study shrinkage and porosity of various fruits and vegetables.

Experimental Studies for Convective Drying of Potato

An experimental facility was built at the Indian Institute of Technology Delhi in order to examine the characteristics of convective drying of a moist object. The test facility consists of an inlet section, a divergent and convergent section, a settling chamber, a test section, and an outlet section. Initial moisture content and time-dependent moisture content of a rectangular shaped moist object (4 cm × 2 cm × 2 cm) are measured by this test facility. The potato slice was selected as a sample moist object. Moisture content was measured at different air temperatures of 40, 50, 60, and 70°C with an air velocity of 2 m/sec. The density of potato slice was determined for various drying temperatures. The volume shrinkage during drying decreased almost linearly with moisture content. The percentage air pores and porosity increased gradually with decreasing moisture content and increasing drying air temperature. Volumes of water, air, and solid content of potato were determined at different drying air temperatures. The results are validated with theoretical data.

Modeling of mass transfer performance of hot-air drying of sweet potato (Ipomoea Batatas L.) slices

In order to investigate the transfer characteristics of the sweet potato drying process, a laboratory convective hot air dryer was applied to study the influences of drying temperature, hot air velocity and thickness of sweet potato slice on the drying process. The experimental data of moisture ratio of sweet potato slices were used to fit the mathematical models, and the effective diffusion coefficients were calculated. The result showed that temperature, velocity and thickness influenced the drying process significantly. The Logarithmic model showed the best fit to experimental drying data for temperature and the Wang and Singh model were found to be the most satisfactory for velocity and thickness. It was also found that, with the increase of temperature from 60 to 80?C, the effective moisture diffusion coefficient varied from 2.962?10-10 to 4.694?10-10 m2?s-1, and it fitted the Arrhenius equation, the activation energy was 23.29 kJ?mol-1; with the increase of hot air velocity from 0.423 to 1.120 m?s-1, the values of effective moisture diffusion coefficient varied from 2.877?10-10 to 3.760?10-10 m2?s-1; with the increase of thickness of sweet potato slice from 0.002 m to 0.004 m, the values of effective moisture diffusion coefficient varied from 3.887?10-10 to 1.225?10-9 m2?s-1.

Investigation into solar drying of potato: effect of sample geometry on drying kinetics and CO2 emissions mitigation.

Drying experiments have been performed with potato cylinders and slices using a laboratory scale designed natural convection mixed-mode solar dryer. The drying data were fitted to eight different mathematical models to predict the drying kinetics, and the validity of these models were evaluated statistically through coefficient of determination (R(2)), root mean square error (RMSE) and reduced chi-square (χ (2)). The present investigation showed that amongst all the mathematical models studied, the Modified Page model was in good agreement with the experimental drying data for both potato cylinders and slices. A mathematical framework has been proposed to estimate the performance of the food dryer in terms of net CO2 emissions mitigation potential along with unit cost of CO2 mitigation arising because of replacement of different fossil fuels by renewable solar energy. For each fossil fuel replaced, the gross annual amount of CO2 as well as net amount of annual CO2 emissions mitigation potential considering CO2 emissions embodied in the manufacture of mixed-mode solar dryer has been estimated. The CO2 mitigation potential and amount of fossil fuels saved while drying potato samples were found to be the maximum for coal followed by light diesel oil and natural gas. It was inferred from the present study that by the year 2020, 23% of CO2 emissions can be mitigated by the use of mixed-mode solar dryer for drying of agricultural products.

Influence of shrinkage on convective drying of fresh vegetables: A theoretical model

The aim of the present work was the formulation of a theoretical model predicting the behavior of a convective drier over a wide range of process conditions. The proposed approach was based on the coupling of a transport phenomena model, describing the simultaneous transfer of momentum, heat and mass both in the drying chamber and in the food, and of a structural mechanics model aimed at estimating food sample deformations, as due to moisture loss. The effects of food shrinkage on drying performance were ascertained by analyzing the spatial distributions of temperature, moisture content, strain and stress, as a function of operating conditions. The agreement between model predictions and a set of experimental data collected during drying of cylindrical potatoes was good as far as the time evolutions of food average moisture content and of its main dimensions, i.e. length and diameter, were concerned.

Kinetics of dehydration of potato and development of baked product based on dehydrated potato

The aims of this study were to determine the kinetics of dehydration of high yielding potato variety (Diamont), to investigate the various process parameters influencing mechanical drying of potatoes and to develop baked product from the dehydrated potato. From the developed equation it was found that the diffusion co-efficient increased with the increase in temperature. The exponential relationship between diffusion co-efficient (De) versus inverse absolute temperature (Tabs-1), activation energy (Ea) for diffusion of water HYV potato was found to be 7.98 Kcal/gm-mole. The influence of loading density as well as thickness of the product on drying rate were determined and the power law equations which described the relationship between drying rate constant and thickness gave an n-value of 0.4586 for HYV of potato. Organoleptic taste tests demonstrated that among biscuits made of various proportion of potato flour and wheat flour, the results of test panel showed that biscuit made of equal proportion (1:1) of potato flour and wheat flour secured the highest score (8.0). All the other samples of each type of product were also accepted by the panelists either as “like moderately” or “like slightly”.DOI: http://dx.doi.org/10.3329/jbau.v10i2.14923 J. Bangladesh Agril. Univ. 10(2): 303-312, 2012

Performance Evaluation and Process Optimization of Potato Drying using Hot Air Oven

The effect of various process parameters on drying behavior of Potato (Solanum tuberosum) was studied, and the optimization of process parameters based on quality was investigated. Experiments were conducted to characterize the drying behavior of Potato cubes at various temperatures, potato cube sizes and blanching chemical treatments. The various drying models were evaluated for their suitability and Midilli’s model was found to be best describing the drying characteristics of Potato cubes. A full second order model was developed for all the response variables, viz. Rehydration ratio, shrinkage percentage and mean sensory scores of overall acceptability and found to be significant at 1% level of significance. The effect of process variables was investigated at individual, linear, interactive and quadratic levels for each response. The data was optimized by ‘Design Expert 7.0’ for all the responses. Compromise optimum level of process variables for the responses were 80°C (1), 1cm cube size (-0.87) & KMS (0). The corresponding values of the responses were 4.584, 24.979 & 5.000 respectively.

Characterization of Fusarium spp. Causing Potato Dry Rot in China and Susceptibility Evaluation of Chinese Potato Germplasm to the Pathogen

Dry rot is a serious potato disease and causes significant losses in China. Research efforts on potato dry rot have been very limited as well as the attempts to characterize the pathogen in the major potato production regions of China. A total of 260 Fusarium isolates were identified in 698 potato tubers collected in six important potato production regions of northern China, out of which five different Fusarium species, Fusarium sambucinum, F. avenaceum, F. oxysporum, F. equiseti, and F. acuminatum, were isolated. The identification of each species was confirmed by sequencing analysis of ∼700 bp DNA fragment derived from the translation elongation factor-1 alpha gene. F. sambucinum was found to be the predominant species accounting for 56% of the isolates. Different pathogenicity was found to be associated with five most common Fusarium species. Sixty-seven clones used in China were identified as susceptible to F. sambucinum, indicating little scope for developing resistant cultivars using the currently available potato germplasm.

Energetic Analysis of Drying Biological Materials with High Moisture Content by Using Microwave Energy

One of the most important parameters in the drying process is the efficiency of energy transfer. Although it is well known that the absorbed component of the referred energy in the dehydration process under microwave conditions is theoretically lower—especially during the falling rate period of drying—by an order of magnitude than that of convective drying, the real efficiency of energy transfer in the microwave field depends on numerous—partly unknown—factors. In this study, the most significant relations between the energy transfer efficiency and the drying parameters were investigated. During the experiments, two power levels were used to study the effects of domain variables in apple, potato, and onion dehydration processes. The results showed that variations in microwave power level played an important role in overall drying kinetics. Based on the recorded data, we determined the typical energy efficiency factors for microwave drying of apple, potato, and onion. The specific energy consumption was calculated to compare the energy efficiency of a single measurement series. It was evident that by applying higher power levels, the energy utilization was more efficient. Furthermore, we theoretically proved and experimentally showed the nonthermal effects of the microwave energy.

Transport in deformable food materials: A poromechanics approach

A comprehensive poromechanics-based modeling framework that can be used to model transport and deformation in food materials under a variety of processing conditions and states (rubbery or glassy) has been developed. Simplifications to the model equations have been developed, based on driving forces for deformation (moisture change and gas pressure development) and on the state of food material for transport. The framework is applied to two completely different food processes (contact heating of hamburger patties and drying of potatoes). The modeling framework is implemented using total Lagrangian mesh for solid momentum balance and Eulerian mesh for transport equations, and validated using experimental data. Transport in liquid phase dominates for both the processes, with hamburger patty shrinking with moisture loss for all moisture contents, while shrinkage in potato stops below a critical moisture content.

Kinetics of potato drying using fluidized bed dryer

The effect of air temperature and two different shapes (cuboidal and cylindrical) with 3 aspect ratio of each shape on the drying kinetics of potato (Solanum tuberosum) in fluidized bed dryer was investigated. Drying was carried out at 50, 60 and 70°C at 7m/s air velocity. Drying data were analysed to obtain effective diffusivity of moisture transfer. During drying moisture transfer from potato were described by Fick's diffusion model. Two mathematical models were fitted to experimental data. The Page model gave better fit than simple exponential model. The Arrehnious activation energy value expresses the effect of temperature on diffusivity.

Improvement of water transport mechanisms during potato drying by applying ultrasound

The drying rate of vegetables is limited by internal moisture diffusion and convective transport mechanisms. The increase of drying air temperature leads to faster water mobility; however, it provokes quality loss in the product and presents a higher energy demand. Therefore, the search for new strategies to improve water mobility during convective drying constitutes a topic of relevant research. The aim of this work was to evaluate the use of power ultrasound to improve convective drying of potato and quantify the influence of the applied power in the water transport mechanisms. Drying kinetics of potato cubes were increased by the ultrasonic application. The influence of power ultrasound was dependent on the ultrasonic power (from 0 to 37 kW m(-3) ), the higher the applied power, the faster the drying kinetic. The diffusion model considering external resistance to mass transfer provided a good fit of drying kinetics. From modelling, it was observed a proportional and significant (P < 0.05) influence of the applied ultrasonic power on the identified kinetic parameters: effective moisture diffusivity and mass transfer coefficient. The ultrasonic application during drying represents an interesting alternative to traditional convective drying by shortening drying time, which may involve an energy saving concerning industrial applications. In addition, the ultrasonic effect in the water transport is based on mechanical phenomena with a low heating capacity, which is highly relevant for drying heat sensitive materials and also for obtaining high-quality dry products.

On-farm evaluation of the impact of drying and storage on the carotenoid content of orange-fleshed sweet potato (Ipomea batata Lam.)

Drying of orange-fleshed sweet potato was evaluated under African rural conditions. Three locally built dryers (open-air sun, tunnel and shade) were tested using Resisto and MGCL01 varieties in Mozambique. Total carotenoid losses were low in all dryers being 9.2% on average. After drying, sweet potato chips were stored in a traditional way (jute bags inside a mud house). Chip size (thin, thick chip or slice) had a significant effect on drying (P < 0.05) but not on storage and variety had an effect on both. Total carotenoid losses during storage were much higher being 83.7% on average, after 4 months, with main individual carotenoids fitting a first-order kinetics degradation. Globally, carotenoid losses on-farm or on-research station were of similar level.

Hot Air Drying Characteristics of Sweet Potato Using Moisture Sorption Isotherm Analysis and Its Quality Changes During Drying

Changes in the quality of sweet potato during hot air drying, such as L-ascorbic acid, sugar content, surface color and hardness, and drying characteristics, were investigated at temperatures of 30, 40, 50, and 60°C. Equilibrium moisture contents (EMC) of sweet potato samples in the desorption process were measured by a static method at the four aforementioned temperatures and six selected relative humidity levels. Using both the measured moisture content data in the drying test and the EMC values, hot air drying characteristics of sweet potato was estimated. Changes in L-ascorbic acid content of sweet potato during hot air drying was measured, wherein a first-order reaction rate equation was applied to model the change in decomposition of L-ascorbic acid content. In addition, surface color, sugar content, and surface hardness were also measured. The total color change (?E) of the samples was observed to decrease as drying temperature was increased. The effects of sample sugar concentration on surface hardening during hot air drying of sweet potato are discussed.

Trichothecene Mycotoxins Associated with Potato Dry Rot Caused by Fusarium graminearum

Fusarium graminearum, a known producer of trichothecene mycotoxins in cereal hosts, has been recently documented as a cause of dry rot of potato tubers in the United States. Due to the uncertainty of trichothecene production in these tubers, a study was conducted to determine the accumulation and diffusion of trichothecenes in potato tubers affected with dry rot caused by F. graminearum. Potato tubers of cv. Russet Burbank were inoculated with 14 F. graminearum isolates from potato, sugar beet, and wheat and incubated at 10 to 12 degrees C for 5 weeks to determine accumulation of trichothecenes in potato tubers during storage. Twelve of the isolates were classified as deoxynivalenol (DON) genotype and two isolates were as nivalenol (NIV) genotype. Trichothecenes were detected only in rotted tissue. DON was detected in all F. graminearum DON genotype isolates up to 39.68 microg/ml in rotted potato tissue. Similarly, both NIV genotype isolates accumulated NIV in rotted potato tissue up to 18.28 microg/ml. Interestingly, isolates classified as genotype DON accumulated both DON and NIV in the dry rot lesion. Potato tubers were then inoculated with two isolates of F. graminearum chemotype DON and incubated up to 7 weeks at 10 to 12 degrees C and assayed for DON diffusion. F. graminearum was recovered from >53% of the isolations from inoculated tubers at 3 cm distal to the rotted tissue after 7 weeks of incubation but DON was not detected in the surrounding tissue. Based in this data, the accumulation of trichothecenes in the asymptomatic tissue surrounding dry rot lesions caused by F. graminearum is minimal in cv. Russet Burbank potato tubers stored for 7 weeks at customary processing storage temperatures.

Modelling of air drying of fresh and blanched sweet potato slices

SummaryEffects of blanching, drying temperatures (50–80 °C) and thickness (5, 10 and 15 mm) on drying characteristics of sweet potato slices were investigated. Lewis, Henderson and Pabis, Modified Page and Page models were tested with the drying patterns. Page and Modified Page models best described the drying curves. Moisture ratio vs. drying time profiles of the models showed high correlation coefficient (R2 = 0.9864–0.9967), and low root mean squared error (RMSE = 0.0018–0.0130) and chi‐squared (χ2 = 3.446 × 10–6–1.03 × 10–2). Drying of sweet potato was predominantly in the falling rate period. The temperature dependence of the diffusion coefficient (Deff) was described by Arrhenius relationship. Deff increased with increasing thickness and air temperature. Deff of fresh and blanched sweet potato slices varied between 6.36 × 10–11–1.78 × 10–9 and 1.25 × 10–10–9.75 × 10–9 m2 s–1, respectively. Activation energy for moisture diffusion of the slices ranged between 11.1 and 30.4 kJ mol–1.