Drying Of Potato Research Articles

Three-dimensional morphological changes of potato slices during the drying process

Hot air drying is a common method for drying potato slices. In this paper, the three-dimensional (3D) morphological changes incurred during hot air drying of potato slices were investigated. The effect of drying on the thickness and diameter of potato slices was of special interest. The results showed that the potato slices underwent stages of regular warping, collapse, and curling during the drying process. After classifying the numerical variation in characteristics into the standard deviation in mean height (SDMH) and the rate of change in mean height (RCMH) of potato slices, the RCMH was selected to describe the 3D morphological changes in the potato drying process. A critical point and a termination point for RCMH of potato slices in the drying process were observed. Samples varied widely after the critical point was reached. A logarithmic function model was used to assess differences in the RCMH at the critical point and the termination point. The R-squared (R2) value of 0.9 suggested a strong correlation between the parameters of the experiment and changes in slice thickness and diameter. The model proposed in this paper could accurately characterize the late-stage changes in potato slice qualities during hot air drying of potato slices.

Экспериментальные исследования сушки картофеля с применением предварительной точечной электропорации

Экспериментальные исследования сушки картофеля с применением предварительной точечной электропорации

Thermodynamic and mathematical analysis of modified Luikov's equations for simultaneous heat and mass transfer

Interface thermodynamic and mathematical analysis of modified Luikov equations (MLEs) for simultaneous heat and mass transfer in solids were developed. The thermodynamic relations at interface show that air-(wet solid) equilibrium relation may be mathematically approximated by two linear segments. These linear relations conduced to the possibility that MLEs have analytical solution for 1D rectangular, 1D radial cylindrical and 1D radial spherical coordinates system; and, the existence of a topology between solutions. The implications of MLEs thermodynamic and mathematical analysis on lumped equations were discussed. Experimental evolution of moisture and temperature during potato drying were compared with MLEs analytical (for one single linear stage at interface) and numerical (for the 2 linear stages) solutions.

Thermodynamic analysis of potato drying process in a microwave dryer

Thermodynamic analysis of potato drying process in a microwave dryer

Application of cold filamentary microplasma pretreatment assisted by thermionic emission for potato drying

Cold filamentary microplasma (CFM) pretreatment assisted by thermionic emission (TE) is a promising, cold drying technology for agricultural products. Such novel pretreatment method based on local electroporation process in the air gap. Brief theory and treatment mechanism are explained. A fractional factorial design 33 was used to determine the effect of CFM treatment assisted by TE parameters such as pulse frequency (F = 40, 80 and 120 Hz), pretreatment duration (D = 60, 120 and 180 s) and temperature of thermionic source (T = 700, 850 and 1000 °C) on drying time and drying rate of potato samples. Maximal CFM pretreatment effect was observed at frequency of 80 Hz, treatment duration of 120 s and temperature of thermionic source of 1000 °C, and the corresponding drying rate and drying time were 35·10−5 (kg/kg s−1) and 130 min. The use of CFM treatment had minor effects on the main quality characteristics (total sugar and starch content) of potato samples. Fourier-transformed infrared spectroscopy confirmed the absence of any modifications of functional group composition of potato samples after CFM pretreatment. Results indicate that cold pulsed filamentary microplasma can enhance the drying rate and decrease drying time without changes in quality characteristics. Practical applicationsCold filamentary microplasma pretreatment assisted by thermionic emission can improve the efficiency of potato drying. Furthermore, it has potential application for reducing energy consumption in drying. CFM pretreatment could be potentially applied for agricultural products drying.

Microwave and Blanching Pretreatments for Hot Air Drying of Orange-Fleshed Sweet Potato Slices (Ipomoea batatas).

Microwave and steam blanching as pretreatments to hot air drying of orange-fleshed sweet potato (OFSP) were studied. The air-drying experiment was performed at constant temperature of 70°C and airflow of 1.0 m/s. The effective moisture diffusivity varied from 1.5 × 10−9 to 4.4 × 10−9 m2/s, and 1.1 × 10−10 to 7.9×10−10 m2/s, for the microwave and blanched assisted hot air drying, respectively. The activation energy obtained for the various microwave-assisted hot air drying was 29.1 W/mm for 4 min, 68.1 W/mm for 3 min, and 79.7 W/mm for 2 min. Ascorbic acid degradation and formation of brown pigments in the OFSP slices were lower in microwave than in steam blanch-assisted drying. Microwave-assisted drying of OFSP is best governed by Page model, MR = exp(−ktn), while the blanch-assisted followed the logarithmic model, MR = a exp(−kt) + c. To produce better quality OFSP flour, it is recommended to cut the tubers into 3 mm slices, microwave at a power of 630 W for 2 min or blanch for 1 min, 43 seconds prior to hot air drying.

Effects of intermittent radio frequency drying on structure and gelatinization properties of native potato flour

Radio frequency (RF) treatment technology has now been studied and used for kinds of food products as its rapid and volumetric heating effects. It is meaningful to study the characteristics of potato drying with a new RF treatment method. In this study, intermitted RF combined treatments were used to get high-efficiency dehydration effects for potato drying, but the impact and mechanism of RF radiation on drying efficiency or quality is still unknown. To explore the drying characteristics, the effects of different RF radiation and the associated intermittent periods on the characterization of color, crystalline, thermal, pasting, rheology, and structural properties of potato flour were systematically studied. Longer RF radiation period (7 min) has a positive effect on drying efficiency and quality. The effect of intermittent period was not as significant as that of RF radiation, but a slightly increasing trend of the quality properties with intermittent period also indicated the tempering effect. The combined action of RF intermittent treatment on potato drying was found and investigated in this study, which may support RF drying processing improvement.

Energetic and exergetic analysis of a convective drier: A case study of potato drying process

Abstract This research work focused on the evaluation of energy and exergy in the convective drying of potato slices. Experiments were conducted at four air temperatures (40, 50, 60 and 70°C) and three air velocities (0.5, 1.0 and 1.5 m/s) in a convective dryer, with circulating heated air. Freshly harvested potatoes with initial moisture content (MC) of 79.9% wet basis were used in this research. The influence of temperature and air velocity was investigated in terms of energy and exergy (energy utilization [EU], energy utilization ratio [EUR], exergy losses and exergy efficiency). The calculations for energy and exergy were based on the first and second laws of thermodynamics. Results indicated that EU, EUR and exergy losses decreased along drying time, while exergy efficiency increased. The specific energy consumption (SEC) varied from 1.94 × 105 to 3.14 × 105 kJ/kg. The exergy loss varied in the range of 0.006 to 0.036 kJ/s and the maximum exergy efficiency obtained was 85.85% at 70°C and 0.5 m/s, while minimum exergy efficiency was 57.07% at 40°C and 1.5 m/s. Moreover, the values of exergetic improvement potential (IP) rate changed between 0.0016 and 0.0046 kJ/s and the highest value occurred for drying at 70°C and 1.5 m/s, whereas the lowest value was for 70°C and 0.5 m/s. As a result, this knowledge will allow the optimization of convective dryers, when operating for the drying of this food product or others, as well as choosing the most appropriate operating conditions that cause the reduction of energy consumption, irreversibilities and losses in the industrial convective drying processes.

The influence of processing conditions on kinetics, anthocyanin profile and antioxidant activity of purple sweet potato subjected to hot air drying

AbstractPurple sweet potato is rich in anthocyanins. The influence of hot air drying on the physical properties, anthocyanin profile and antioxidant capacity of purple sweet potato was explored at six different temperatures (60, 70, 80, 90, 100, and 110°C), three different paving densities and six different dimensions. The results show that the hot air drying kinetics of purple sweet potato were best described by the Page model. The samples dried at 60°C had the highest rehydration rate (2.64), and there was no significant difference between 80 and 60°C. There were no significant differences among the colors of the samples dried at 60, 70, 80, and 90°C, but they were quite different from that dried at 110°C. Four anthocyanins were identified by HPLC–MS/MS as cyanidin 3‐sophoroside‐5‐glucoside, peonidin 3‐sophoroside‐5‐glucoside, cyanidin 3‐p‐hydroxybenzoylsophoroside‐5‐glucoside and peonidin 3‐p‐hydroxybenzoylsophoroside‐5‐glucoside and determined by HPLC‐DAD, and the anthocyanin contents of the samples dried at 80°C were 609.08 ± 3.26, 82.75 ± 0.33, 265.88 ± 0.93, and 179.74 ± 1.35 mg/100 g DW, respectively. The highest ORAC antioxidant capacity was found in samples dried at 80°C (130.94 ± 2.59 μmol TE/g). Based on these studies, 80°C is most suitable for the hot air drying of purple sweet potato.Practical applicationsPurple sweet potatoes have good antioxidant capacity, which is good for health and loved by consumers. Fresh purple sweet potatoes are not easy to store, but the storage time can be prolonged after hot air drying. This study detected the influence of hot air drying on the drying kinetic, color, rehydration, microstructure, and anthocyanin content of purple sweet potato. Compared with dimension and paving density, the influence of drying temperature is greater. Among six temperatures, 80°C is most suitable for the hot air drying of purple sweet potato. This study provides a theoretical basis for the development and utilization of purple sweet potato as a functional food.

Modeling the drying of ultrasound and glucose pretreated sweet potatoes: The impact on phytochemical and functional groups

The influence of ultrasonic frequency (20 kHz) and glucose pretreatments either alone or in combination on the drying of sweet potato slices (3 mm) using a hot-air dryer at 60 °C was tested to study the kinetics modeling, phytochemicals, antioxidant activities, and functional and textural changes of the final dried product. The results indicated that total phenolic content and total flavonoid content were significantly higher in glucose-pretreated samples while antioxidant activities were higher in ultrasound- and glucose-pretreated samples. For vitamin C, much degradation occurred in the glucose-pretreated samples when compared with the other pretreated samples apart from the control. Enzymatic browning made a minor contribution to the ultrasound/glucose-pretreated samples, while no significant differences were noted in the glucose-pretreated samples. A modified Henderson and Pabis (MHP) model, followed by the two-term and Hii models, fitted best among the 15 selected mathematical models. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the presence of glucose, phenols, and flavonols in all samples. Microstructural analysis confirmed the hardness (N) in the final glucose-pretreated samples due to glucose layers and less cell damage.

Numerical Simulation of the Drying Kinetics of Sweet Potato to Prevent the Growth of the Fungi Rhizopus oryzae

Sweet potatoes are prone to fungi Rhizopus oryzae that results in fast spoilage upon delivery due to its moisture content which can develop fungi that can give foul odor and color. The decrease in moisture content can prolong the shelf-life of the sweet potato. This problem can be addressed by a drying process where a hot tray air dryer was used. Sweet potatoes were cut to 5x5x30 mm uniformly and dried it at 40°C, 50°C, 60°C until the constant weight of the batch was obtained. Laplace Transform Model, Non-Linear Decomposition Model, and Page Model are the three mathematical model that were compared to determine what is the best fit for the drying of the sweet potato. Based on data gathered, Page Model is the best fit at 60˚C. Page Model fitted best from the other two models with an average drying time of 115 minutes and 46 mins to obtain the desired moisture content of 10%.

Optimization of the blanching of potato (Solanum tuberosum L) slices by response surface methodology: Effect on the vitamin C content and drying kinetics

Potatoes (S. tuberosum L) is one of the most important tuber crops in the world. However, its high moisture content and inadequate storage and processing techniques have a negative influence on its quality and availability throughout the year. This work was carried out to optimize the blanching behavior and drying kinetics of potato slices. Fresh potato slices (5, 10 and 15 mm) were blanched at 70, 80 and 90°C for 1, 3 and 5 min following a 3k level full factorial design. The loss in Vitamin C was used as a quality marker for the optimization process. The influence of blanching on the drying behavior of potato slices was carried out at 50, 60 and 70°C. Results showed that blanching parameters had a significant (P < 0.05) effect on vitamin C loss. Optimum blanching conditions were blanching temperature of 80oC, blanching time of 3 min and a slice thickness of 10 mm which gave an average loss in Vitamin C of about 2.6%. Drying data were successfully fitted to three different thin layer drying models. The use of blanching as a pretreatment before the drying of potato is recommended because it reduces the drying time by 30%.

Evaluation of optimization techniques in predicting optimum moisture content reduction in drying potato slices

The use of artificial intelligence models in predicting the moisture content reduction in the drying of potato (Ipomoea batata) slices was the focus of this work. The models used were adaptive neuro fuzzy inference systems (ANFIS), artificial neural network (ANN) and response surface methodology (RSM). The parameters considered were drying time, drying air speed and temperature. The capability and sensitivity analysis of the three models were evaluated using the correlation coefficient (R2) and some statistical error functions such as the average relative error (ARE), root mean square error (RMSE), Hybrid Fractional Error Function (HYBRID) and absolute average relative error (AARE). The result showed that the three models demonstrated significant predictive behaviour with R2 of 0.998, 0.997 and 0.998 for ANFIS, ANN and RSM respectively. The calculated error functions of ARE (RSM = 1.778, ANFIS = 1.665 and ANN = 4.282) and RMSE (RSM = 0.0273, ANFIS = 0.0282 and ANN = 0.1178) suggested good harmony between the experimental and predicted values. It was concluded that though the three models gave adequate predictions that were in good agreement with the experimental data, the RSM and ANFIS gave better model prediction than ANN.

Consideration of Size and Dimension in the Evaluation of Transfers during Convective Drying of Sweet Potato

This work is interested in solving the complex problem of understanding mass transfers in biological media. The contribution of the initial sample size is taken into account. Transfers are established more efficiently in small samples. Thus, from the first 50 minutes, the cubic sample at 1 cm stop is already at 50% while the sample at 4 cm edge is at about 90% of its initial water content. Likewise the shape is combined with the size. But it is revealed that if we fix similar characteristic dimensions, we can bypass the notion of initial shape. Thus the cubic samples 4 cm of edges. 4 cm diameter of spherical shape, 4 cm × 4 cm height-diameter cylindrical one, all dry identically.

Suitability of potato varieties grown from true seed and seed tubers for chips making using a microwave oven

One of the basic concepts of microwave drying of potato (Solanum tuberosum) chips is to achieve desired chip colour and texture, within a short period. In this study, chips (1 mm thickness) of true potato seed (TPS) (‘BARI TPS-1’) and seed potato (‘Asterix’) varieties were heated for 0, 10, 20, 30, 60, 90, 120, 180 and 300 s by a microwave oven, and the changes in chips were analysed physiologically and histologically to investigate the suitability of TPS tubers as processing potato. Although potato chip crispiness of both potato varieties increased continuously throughout the heating treatment, crispiness of ‘BARI TPS-1’, increased more slowly than that of ‘Asterix’, indicating that TPS chips became less rigid and fluffy after microwave heating than that of ‘Asterix’ chips. SEM images of starch granules showed slower swelling and deformed structure in TPS than in ‘Asterix’, suggesting that TPS can retain crisp texture longer than ‘Asterix’. Although there was no substantial increase of a* and b* value in both potato chips, a lower value of L* and crispiness in TPS, suggests TPS chips lose crispiness and colour within a shorter period of microwave heating than ‘Asterix’.Key words: Colour, crispiness, Solanum tuberosum, TPS

Far Infrared Drying Characteristics of the Microwave-Steamed Sweet Potato

In this study, we aimed to investigate far infrared drying characteristics of microwave-steamed sweet potatoes and to establish optimum far infrared drying conditions. The sweet potatoes steamed by microwave for 15 min were far-infrared-dried to a final moisture content of 25 ± 0.5% (w.b.) base on the dried sweet potato sold on the market. The thickness conditions were 2 conditions of 8 mm and 10 mm. The far infrared drying conditions were drying temperature of 60, 70, and 80 °C and air velocity of 0.6 and 0.8 m/s. Optimum microwave steam time for sweet potatoes was 15 min. The far infrared drying time of microwave-steamed sweet potatoes showed a tendency to shorten as the drying temperature was high, the air velocity was fast, and the thickness was thinner. The color difference was lower in the condition of low drying temperature, the slow air velocity, and the thin thickness. Soluble solids contents after far infrared drying increased by 3.09~6.49 Brix compared with that of before drying. Moreover, the soluble solids contents were increased with thinner thickness, higher drying temperature, and slower air velocity. The energy consumption to remove 1 kg of moisture was decreased in the condition of high drying temperature, slow air velocity, and thin thickness. The using of microwave steam process instead of conventional water steam process as pre-treatment before the drying of sweet potato was considered to have the advantage such as decreased drying time, lower color difference, and lower energy consumption.

Effect of Non-Conventional Drying Methods on In Vitro Starch Digestibility Assessment of Cooked Potato Genotypes.

Potatoes (Solanum tuberosum L.) are a good dietary source of carbohydrates in the form of digestible starch (DS) and resistant starch (RS). As increased RS content consumption can be associated with decreased chronic disease risk, breeding efforts have focused on identifying potato varieties with higher RS content, which requires high-throughput analysis of starch profiles. For this purpose, freeze drying of potatoes has been used but this approach leads to inaccurate RS values. The present study objective was to assess the starch content (RS, DS and total starch (TS)) of three cooked potato genotypes that were dried using freeze drying and innovative drying techniques (microwave vacuum drying, instant controlled pressure drop drying and conductive hydro-drying) relative to freshly cooked potato samples. Depending on the genotype, all drying methods showed one or more starch measures that were significantly different from freshly cooked values. The combination of ultrasound and infrared assisted conductive hydro-drying was the only method identified to be associated with accurate assessment of DS and TS content relative to fresh samples. The drying treatments were all generally associated with highly variable RS content relative to fresh controls. We conclude that freshly cooked samples must be used for selecting varieties with a high proportion of RS starch as drying of cooked potatoes leads to unreliable RS measurements.

Experimental Investigation of Drying Potato for Karaikal Climatic Condition

Vegetables play an important and irreplaceable role in the human beings daily life and other living animals on the planet. Henceforth, wastage of vegetables should be kept away by developing techniques for conservation and preservation of vegetables to an extended period. In this article, a double slope solar dryer was designed and fabricated at the terrace of the science block, NIT Puducherry, Karaikal. The decrease in the wetness content of specimens in the double slope solar dryer was empirically inspected for Karaikal climatic conditions. The effect of double slope natural convective based solar dryer in drying of potato compared with open sun drying operation adjacent each other in similar condition. Experiments were carried out to determine the dryer surface temperatures, air temperature, and the percentages of the wet basis wetness content from 11.00 am to 6.00 pm for two days. In the investigation, it was clear that designed and fabricated double slope natural convective solar powered dryer removed the high wetness content about 52.29% and in open drying technique it removed wetness content of 42.99% from the potato slices on first day. On second day similar weighted samples were investigated wetness removed by solar dryer is 51% and 43.92% in open drying. So developed solar dryer removed high amount wetness content and quality of dried potato slices was high when compared to open sun dehydrating. Accordingly, the developed double slope natural convective based solar dryer can be effectively utilized to dry the vegetable samples.

Multi‐frequency ultrasound and sequential infrared drying on drying kinetics, thermodynamic properties, and quality assessment of sweet potatoes

AbstractDifferent ultrasound frequencies as pretreatments with different infrared drying temperatures were tested for drying of sweet potatoes to study the drying kinetics, mathematical modeling, energy activation, and thermodynamic properties of dried sweet potatoes. The treated samples showed a significant reduction in drying time by 110 to 60 min as compared to the control ones. Hii model, Page model, and Silva models found satisfactorily described the drying kinetics among 13 different tested mathematical models. The effective diffusion varied from 1.01 × 10−06 to 9.21 × 10−06, while the lowest activation energy recorded as 24.69 kJ/mol in samples pretreated with 40 kHz. The enthalpy and Gibbs free energy decreased with the increase in drying temperature while entropy decreased and obtained as negative during drying. In addition, the moderate ultrasound frequency of 40 kHz positively and significantly (p < 0.05) influenced the surface color, enzyme inactivation, enzymatic browning, and microstructure of dried sweet potatoes.Practical applicationsThis study investigated the impact of sequential ultrasound (US) frequencies and infrared (IR) temperatures. The study provides significant evidence that the US in combination with IR not only reduces drying time but also improve the quality of the dry product on moderate US frequency. Higher US frequency (60 kHz) at higher temperature did not significantly improve the drying time but also showed big pores in SEM analysis.

Impact of mineral ions on the release of starch and gel forming capacity of potato flakes in relation to water dynamics and oil uptake during the production of snacks made thereof.

Potato flakes (PFs) are made by boiling, mashing and subsequent drying of steam peeled potatoes. Their cold-water swelling starch readily develops viscosity upon hydration. That potato starch amylopectin (AP) contains esterified phosphate groups results in rapid swelling and high viscosity of PF suspensions. This study is the first report on the impact of sodium, calcium and aluminum chloride on (i) the physicochemical properties of PFs and (ii) the water dynamics in relation to oil uptake in the production of deep-fried crisps made thereof. Adding 125 μmol cation/g PF dry matter (dm) of these salts to PF suspensions (8.0% dm) in a Rapid Visco Analyzer (RVA) decreased the peak viscosities by 5% (sodium chloride) and 20% (calcium or aluminum chloride). While monovalent cations shield the negative charges of the phosphate monoesters on the starch chains, divalent and trivalent cations bridge phosphate groups of adjacent AP molecules and thereby reduce swelling even further. Moreover, the latter ions result in up to 20% higher RVA cold paste viscosity readings even if they do not affect amylose (AM) aggregation. They thus enhance the gelation of PFs by AP bridging. For producing deep-fried crisps, PFs, emulsifier and maltodextrin were hydrated, mixed, sheeted into dough, and deep-fried. Including the above dosage of calcium ions in its recipe increased the specific strength of the dough sheet by about 15%. Time domain proton nuclear magnetic resonance analysis of dough sheets showed that these ions increase the rigidity of the starchy gel network while AM crystallization remains largely unaffected. This is evidence that ionic cross-linking of AP directly strengthens the dough sheet. Moreover, the calcium ions lowered the lipid content of the deep-fried crisps by about 5% due to stronger interaction of starch polymers with water. Ionic cross-linking of AP thus improves the gel forming capacity of PFs and strengthens the starchy gel network during manufacturing of potato-based snacks resulting in crisps with a significantly lower lipid content.