Solar Dehydration Research Articles

Inactivation kinetics of Bacillus cereus and Aspergillus niger spores in dehydrated onion shreds after pulsed light and infrared treatments

Fresh onions are dehydrated to increase their shelf-life. Primarily, open dehydration techniques like solar dehydration come with the problem of contamination through natural air convection. A solar conduction dryer that uses conduction, convection, and radiation for dehydration of food samples is exploited in this study. The food samples are often contaminated by Bacillus and Aspergillus species spores. As a remedy, pulsed light treatment as a non-thermal technology and infrared treatment as a thermal technology are studied and compared. Bacillus cereus and Aspergillus niger spores are chosen as a representative of bacterial and fungal contamination in onions. Dehydrated onion shreds with varying water activities (0.4, 0.5, 0.6) were treated. The spore inactivation was best described by Weibull model as compared with first-order model. Scanning electron microscopy images of the microbial cells showed surface distortions on the bacterial and fungal spores. The effect of the treatment technologies on the colour, flavour (thiosulphinate and pyruvic acid concentration), total phenolic and flavonoid content, and ascorbic acid concentration are compared. Overall, pulsed light treatment showed promising inactivation with a maximum log reduction of 4.5 log B. cereus spores·g−1 and 3.1 log A. niger spores·g−1 at 2.131 J·cm−2 in samples with water activity 0.6. The inactivation rate increased with an increase in water activity. The colour was better retained in pulsed light treated samples. The thiosulphinate content (9.24 μmol·g−1), total phenolics (0.268 mg GAE·g−1), and flavonoid content (0.344 mg QE·g−1) in the sample were improved upon pulsed light exposure.Graphical

A Review Paper on CFD Analysis of Solar Dehydration System

A Review Paper on CFD Analysis of Solar Dehydration System

دراسة التأثير الحراري لعملية تجفيف الطماطم باستخدام نظام الطاقة الشمسي

This study developed a hybrid solar greenhouse dryer (lean-to) incorporated with a solar collector and photovoltaic (PV) system for smallholder processors of tomatoes and evaluated the thermal performance of forced convection mixed-mode solar dryer with two pretreatments of fresh tomatoes (halves and slices) with salt and sugar. Tomatoes dipped in a 40% sucrose solution for 72 hours before drying exhibited a greater initial drying rate than those treated with salt. The hourly average incident solar radiation without a reflector was 673.8 (±214.2) W/m2 outside and 754.6 (±284.5) W/m2 inside the lean-to solar dehydrator during operation. The incident solar radiation in the collector ranged from 390.3 to 1156.0 W/m2, indicating higher levels at the tilt angle. The hourly average air temperatures outside and inside the solar dehydrator and solar collector during the experiment, respectively, were 30.7 (±2.3), 52.7 (±10.1), and 30.7 (±2.3), 79.7 (±26.9)°C for the salt treatment and 31.0 (±2.0), 55.1 (±15.3), and 31.0 (±2.0), 84.8 (±28.0)°C for the sugar treatment. Thus, the solar dehydrator and the solar collector raised the dehydrating air temperatures over the outside for the salt and sugar treatment by an average of 22.0, 49.0, 24.1, and 53.8ºC, respectively. The average hourly air-relative humidity inside the solar dehydrator was 33.5%, while outside was 47.2%. The pretreated tomatoes had an initial moisture content of 93.1% (w.b). The solar dehydrator's thermal efficiency was 72.21%, and its drying efficiency was 56.48%. Consequently, solar energy contributed 84.28 and 71.18% of the generated heating power. The solar dehydrator lost 15.72 and 28.82% of its remaining solar energy due to exhausted air. The solar dehydrator had a daily average energy of 59.375 kWh, and the heating power was 47.473 kWh during the experimental period (29 h).

Effect of pre-drying treatments on the quality of solar-dehydrated tomato (Lycopersicon esculentum L.) fruits

Preserving surplus highly perishable products, such as tomatoes, through processing is an effective method, especially during periods of excess supply. Pre-treatment is commonly employed before the drying of agricultural goods to deactivate enzymes, expedite the drying process, and enhance the quality of the resulting dried products. An experiment was done to assess the impact of applying Sodium Metabisulphate, Sodium Chloride, and lemon juice as treatments on the quality of solar-dehydrated tomato (SDT) fruits. The trial consisted of four treatments, organized in a completely randomized design with three replications. The findings demonstrated a substantial increase in protein, crude fat, and total soluble solids levels in the treated samples compared to the control. Moisture content reduced from 96.70 %(wb) to 3.4 % for (db) for the sample pretreated with 5 % lemon juice which was higher than NaCl, SMBS, and Control samples with 3.1 %, 3.2 %, and 3.3 % (db) The experiment has shown that pre-drying treatment of tomato fruits with SMBS, and Lemon juice leads to increased levels of protein with 0.79 g in the treated sample, crude fat recorded at 3.2 % in the lemon juice sample, 10.72% of ash content in lemon juice, and 6.0% of total soluble sugars in lemon juice. Nevertheless, the Lemon juice, NaCl, and control samples exhibited comparable characteristics in terms of color, flavor, taste, and overall acceptability In contrast, the SMBS treatment resulted in superior color with 7.1 %, taste 7.2 %, and 8.3 % for general acceptance as indicated by a significant difference (p = 0.05). Hence, employing solar dehydration as a method to preserve the quality and extend the storage life of treated tomato fruits can serve as a viable technological alternative. Producers, processors, and traders of tomato fruits in Ghana can benefit from using Sodium Metabisulphate, Sodium Chloride, and lemon juice treatments.

Optimization of olive pomace dehydration process through the integration of computational fluid dynamics and deep learning

ABSTRACT This study introduces an innovative approach to optimize the dehydration process of olive pomace by combining computational fluid dynamics (CFD) and deep learning. Through CFD, it identifies the optimal air inlet velocity in a prototype of a passive direct solar dehydrator for olive pomace, which allows for the reduction of its moisture content for subsequent use as biomass. The prototype was simulated in ANSYS software, and this simulation consisted of the following steps: prototype design, meshing, selection of physical models, material assignment, boundary condition simulation, and validation of results with data obtained from the prototype. Following this process, it was concluded that the optimal air inlet velocity to the dehydration chamber is 0.1 m/s. Concurrently, an artificial neural network model was used to analyze data from sensors in the physical prototype, revealing that solar radiation and ambient temperature are the most influential variables on the temperature of the dehydration chamber. This analysis resulted in a predictive model for the optimization of the dehydration process, with a correlation coefficient of 0.9699 for temp_up and 0.9710 for temp_down, and a Willmott coefficient of 0.9999, demonstrating a high concordance between the model’s predictions and the experimental data. The model’s input variables include solar radiation, ambient temperature, and both external and internal air humidity. This integration of CFD and deep learning offers a promising methodology for improving olive pomace dehydration systems and the industry in general.

Performance Assessment of Affordable Solar Dehydrator for Sustainable Energy

Dehydration has long been the preferred method of food preservation over all other techniques. In contrast to other techniques, dehydration uses heat to evaporate extra water from food. This can be simply obtained through solar energy. This work aims to apply appropriate engineering methods to use solar energy for food dehydration efficiently. This work prioritizes both food quality and cost equally. In addition, it features a backup system that operates at night to continuously dehydrate food items with drying times longer than 12 hours, in contrast to previous approaches that are either costly or result in lower-quality products. So, the solar collector is designed at an optimum angle of 27ᵒ with an area of 0.5153 m² to collect useful heat from the sun that develops enough temperature difference to dehydrate some selected food. Experiment results show that the desired purpose is greatly achieved by comparing the dehydrated products with the conventional or commercially available products.

Crystallization Cycles in Masonry Walls: Experimental Technique to Develop Accelerated Aging on a Real Scale

Moisture in historic built heritage is one of the main degenerative agents, because it supports or manifests itself through multiple pathologies. Current knowledge allows for the diagnosis and assessment of the problem, but there are deficiencies in the evaluation of corrective systems due to the time it takes for moisture to become significant. In response, this study proposes an experimental methodology that aims to reproduce the accelerated aging of real scale specimens under laboratory conditions. Thereby improving the understanding of the impact of moisture related deterioration on masonry structures. To achive this, eight masonry walls were constructed and subjected to eight cycles of sulfate crystallization. They were saturated with different sulfate concentrations (5% or 10%) and exposed to different drying conditions (outdoor or solar dehydrator) in order to identify the factors favoring sulfate crystallization and the resulting deterioration. The progress of the experiments was monitored using a hygrometer, a thermographic camera and photogrammetry. The results indicate that it is possible to induce efflorescence in real scale specimens. Temperature and moisture monitoring helped identify the solar dehydrator as a more effective drying treatment. While digital photogrammetry was considered inefficient for quantifying volumetric damage, since this technique can present errors greater than 2%, a value exceeding the observed wear. Reason why the weight of material detached at the end of the experiment was recorded and a positive correlation between the increase in sulfate concentration and the use of the dehydrator was observed. Finally, pertinent considerations are made to improve the experimental conditions.

CFD investigation of the behavior of a solar dryer for the dehydration of olive pomace

ABSTRACT CFD investigation of the behavior of a solar dryer for the dehydration of olive pomace Solar dehydration is a process that reduces the percentage of moisture in the product without using nonrenewable energy. The present research analyses the behavior of olive pomace in the drying process. This process is important due to the need to reduce its humidity since with low humidity, olive pomace has good energy potential and can be used as biomass. The drying curve is determined in which a reduction from 67.34 to 40.73% of humidity can be observed in 12 days of dehydration, and the lower heating value curve and the elemental analysis of the olive pomace sample collected in the olive mill are determined experimentally in the solar dehydrator and in a laboratory. The dehydrator is analyzed with the help of computational fluid dynamics in ANSYS Student software. In this study, attention was focused on observing the effects produced by variations in the height of the dehydration chamber, and it was determined that the optimal height of the dehydration chamber is 300 mm.

OPTIMIZATION OF THERMO-FLOW IN A SOLAR FOOD DEHYDRATOR USING COMPUTATIONAL TECHNIQUES

A solar food dehydrator converts solar energy into heat required to remove moisture from food. This study involved development of an optimized design for a solar dehydrator using computational techniques. A computer-aided design of six (6) different configurations of the dehydrator was developed, and a remotely-installed heat capture device was modelled and analysed using MATLAB. The results show that the Parabolic Trough Collector (PTC) could be used in effectively transferring heat remotely to a dehydrator. The temperature of air leaving the heat exchanger increases in proportion to the increase in the temperature of the heating fluid entering the heat exchanger. Computational Fluid Dynamics (CFD) in Ansys Fluent was employed to aid in the study of airflow and temperature distribution. The hot air was simulated at 2 m/s and 350 K inlet conditions. The CFD simulation results showed significant variations in the air velocity distribution and temperature for different configurations of the dehydrator. The back inflow - front outflow configuration provided the most uniform distribution of heated air in the drying chamber, with minimal variation on each tray. This uniformity was also observed in the distribution of static temperature. The back inflow – side outflow configuration showed a similar performance in flow and temperature distribution. However, the bottom inflow – top outflow and bottom inflow – front outflow configurations showed uneven velocity and temperature distribution inside the drying chamber. Supply of airflow across the trays horizontally provides best airflow and temperature distribution in solar dehydrators and thus highly recommended.

Camu-Camu Flour Processed in Conventional Oven and Solar Dryer: Quality Product and Accessible Low Technology Products as an Opportunity to Family Agriculture

The culture of camu-camu fruit is one of the most promising in the Amazon region; with proper industrialization the fruit could contribute to local food security, which raises excellent opportunities to further elaborate products with higher aggregate value to introduce to population living in natural producing areas. The aim of this research was to carry out a comparison of the agro-industrial and nutritional quality of fruit flour prototypes and residues from the processing of camu-camu dehydrated in a conventional electric oven and an alternative solar dryer, verifying the possibility of obtaining a standardized flour product with the techniques used. The camu-camu fruits was harvested in March of 2018 at Morena Lake, Boa Vista municipality, Roraima State, Brazil and, processed into flour at Embrapa Laboratories. Furthermore, an analysis of moisture, soluble solids, titratable acidity, pH, color and N, P, K, Ca, Mg, S, Cu, Zn, Mn, Fe and B contents of the flour, were carried out and evaluated. The experimental design was completely randomized in a factorial scheme, evaluating three raw materials by two drying methods. The data was statistically validated using an analysis of variance, when there was statistical difference, the means of agroindustrial and elemental characteristics were compared by the T (0.05) and Tukey (0.05) tests. The main quality differences in the interaction between raw materials and drying methods are in moisture, soluble solids, titratable acidity, color and P, K and Ca contents. In general, the macro and microelement contents of the camu-camu flour dehydrated in a hot air oven with forced ventilation, and in a low-cost convection solar dehydrator presented the following order N > K > P > Ca > S > Mg > Mn > Fe > B > Zn > Cu. The evaluated camu-camu flours are presented as alternatives for the integral use of the fruit and processing residues, having satisfactory qualities, with the possibility of being used in agro-industrial products.

Efecto de dos métodos artesanales de carbonización en la elaboración de carbón a partir de semilla de aguaje (Mauritia flexuosa)

The production of coal from biomass emerges as a sustainable alternative, both to take advantage of waste and to protect the environment. This research aims to take advantage of aguaje seeds to make ecochar. First, the seeds (from Pucallpa and Yurimaguas) were characterized proximally. They were then characterized morphologically (length, diameter, and weight), both fresh and dehydrated. In the second part,the carbonization was carried out, using a Completely Random Design with factorial arrangement. The first factor was the state of the seed (fresh and dehydrated), and the second was the carbonization method (open and boxed), the response variable being yield. In the third stage, briquettes were made, mainly evaluating the calorific value. The results showed that solar dehydration similarly reduced the weight of the seeds. The state of the seed and the carbonization method have a significant effect on the yield, being the best treatment with dry seed and open carbonization (yield 25.77%). This treatment also obtained the highest calorific value (6716.93 cal/g) in the final briquettes, higher by almost 25% than that of traditional briquettes.

Armillaria mellea (Vahl. : Fr.) P. Kumm. a non-timber forest resource in the Ñhöñho culture: promoting sustainable development and ethnomycotourism

Background. The indigenous and mestizo communities in Mexico have used Armillaria mellea as a non-timber forest resource, mainly as food; ecologically it is an abundant species in forests. For this reason, we establish A. mellea as a species with cultural importance and a high potential for the development of sustainable regional and ethnomycotourism projects. Methods. The field work was carried out in the Ñhöñho communities of Texquedó and Xahai, Querétaro; Mexico. Semi-structured surveys were applied to local specialists in collecting mushrooms. Species were identified at the taxonomic level. Participation-action workshops were held for the organization and development of ethnomycotourism events. Results. A total biomass of 107.11 kg of A. mellea was collected with the support of the “hongueros” (local mushroom collectors) during the rainy seasons of 2017, 2018 and 2019. A greenhouse-type solar dehydrator was designed to process the mushrooms with a minimum dehydration capacity of 30 and a maximum of 100 kg of fresh mushrooms; and value-added products were designed with edible wild mushrooms. On the other hand, tours and mushroom collections (edible and inedible) were designed with local specialists, academics and visitors; promoting and laying the foundations for the development of ethnomycotourism with an approximate economic income per year in each community of 700 to 1200 dollars. Finally, as a result of this project, the non-profit civil organization; Ethnomycology, Research and Community Development A.C. Conclusion. Mushrooms constitute the basis for the planning of regional sustainable projects, as means of revaluing traditional systems, and strengthening the local economy, as well as conservation and management under a biocultural approach. Keywords. Mycotourism, Ethnomycotourism, Value-added products, Edible wild mushrooms, Otomí, Mexico

Dehydration: An efficient process for ensuring food conservation in vulnerable regions

Approximately 860 million people throughout the world currently live in extreme hunger and poverty due to income reductions, unemployment, and layoffs from the COVID-19 pandemic, all of which disproportionately affect disadvantaged homes (Unated Nations, 2022). One of the objectives of the World Bank (2022) for 2030 is to end extreme poverty and promote shared prosperity. In Mexico, there are 55.7 million people in poverty, extreme poverty, high or very high marginalization, and vulnerable situations on account of lack of food, healthcare, housing, and employment (CONEVAL, 2020). However, there is no immediate solution to rid the world of poverty and food shortage. In this project, we propose to combat the issue of poverty and food inequality with a system for conserving food that takes advantage of the solar energy available in the most disadvantaged and marginalized regions. The solar dehydration used to naturally dry fruits, vegetables, and animal proteins after the harvest will contribute to the food supply, do no harm to the environment, and create an alternative job source.

Design and Performance Evaluation of Hybrid Photovoltaic Thermal Solar Dehydrator

This paper reported on the design and performance evaluation of a hybrid photovoltaic thermal solar dehydrator. The dehydrator is designed to suit the needs of household users and small industries and works using a hot air mechanism. The design process commenced with the initial sketches to collect related ideas and design concepts. The design was then proceeded to concept evaluation through a decision matrix to select the best option. The final design was then converted via computer-aided design (CAD), SolidWorks 2021 to a 3D model and fabricated into a full-scale prototype. The drying performance of the dehydrator on food was evaluated and compared with traditional drying under the meteorological conditions of Panchor, Muar, Malaysia. Heat accumulated inside the dehydrator resulted in a temperature of 44.1 degrees Celsius which is 20 % higher than the ambient temperature. The performance analysis demonstrated that the drying speed of a hybrid solar dehydrator is moderately slower than traditional drying, but it provided a more hygienic drying environment and preserved the color and nutrition value of food products.

Design and Performance Evaluation of Hybrid Photovoltaic Thermal Solar Dehydrator

This paper reported on the design and performance evaluation of a hybrid photovoltaic thermal solar dehydrator. The dehydrator is designed to suit the needs of household users and small industries and works using a hot air mechanism. The design process commenced with the initial sketches to collect related ideas and design concepts. The design was then proceeded to concept evaluation through a decision matrix to select the best option. The final design was then converted via computer-aided design (CAD), SolidWorks 2021 to a 3D model and fabricated into a full-scale prototype. The drying performance of the dehydrator on food was evaluated and compared with traditional drying under the meteorological conditions of Panchor, Muar, Malaysia. Heat accumulated inside the dehydrator resulted in a temperature of 44.1 degrees Celsius which is 20 % higher than the ambient temperature. The performance analysis demonstrated that the drying speed of a hybrid solar dehydrator is moderately slower than traditional drying, but it provided a more hygienic drying environment and preserved the color and nutrition value of food products.

Validation of Solar Dehydrator for Food Drying Applications: A Granny Smith Apple Study

Food loss is a global issue that may be alleviated with effective dehydration strategies. Solar dehydration, rather than traditional sun-drying, is one method that could allow for the safe, efficient preservation of food materials. In this study, passive solar dehydration was achieved using a psychrometric chamber to model the environment of sub-Saharan Africa, where the temperature was the major focus (24.3 °C to 29.4 °C). A mass decrease of 88.56% was achieved within 9 hours. Microbial testing (total aerobic bacteria, Gram-negative bacteria, and total yeasts and molds) demonstrated no difference (all negative) between food stored at 4 °C and dehydrated food, indicating that the dehydrator introduced no new contamination. A 16.0% decrease in vitamin C (VC) concentration was observed due to the lability of VC. Insight into the visual appeal of the food samples was provided by measuring browning values, where it was found that dehydrated green apples are significantly less brown than the sample exposed to air for the same length of time. Passive solar dehydrators could provide a simple method to reduce food waste and maintain nutritional content and visual appeal.

Effect of pretreatments on solar dehydration of different varieties of apple (Malus domestica)

In this study, four different apple varieties were dried in a solar tunnel dryer using four different methods. Apple slices were immersed in a solution consisting of 0.5% ascorbic acid, 0.5% sodium metabisulphite, and 0.5% citric acid for 3 min. Constant measurements were performed in various parts of the dryer for drying air temperature, solar irradiation, air velocity, and relative humidity during drying. The change in the mass of apples was measured on a daily basis. Furthermore, ten mathematical models were used to study the drying process, which were Newton, Page, Henderson and Pabis, logarithmic, diffusion, two-term, two-term exponential, Midilli, Alibas, and logistic equation. Then, these models were compared in terms of their performance levels based on correlation coefficient (R<sup>2</sup>), chi-square value (χ<sup>2</sup>), and root mean square error (RMSE) between moisture ratios (MR) that were observed and predicted. Furthermore, we observed that the Alibas model and the two-term model revealed the ratio of drying in a satisfactory way for all drying methods.

Drying of Carrot Strips in Indirect Solar Dehydrator with Photovoltaic Cell and Thermal Energy Storage

Minimizing agricultural losses, accompanied by employing technologies capable of taking advantage of solar energy, are the current challenges of the Antofagasta region of Chile due to having an average solar irradiance of 7.2 kWh/m2 per day. With this objective, using an indirect solar dryer with storage of thermal energy in the form of sensible heat, the effect of drying on the quality of carrot strips was studied using chromatic coordinates CIEL*a*b*, the color difference (ΔE), the relationship between redness/yellowness (R = a*/b*), browning index (BI), whiteness index (WI), chroma (C), hue angle (h°) and drying kinetics. The experimental drying data were fitted to 15 typically employed nonlinear regression models. The ΔE = 14.11 ± 0.14 between the carrots in the dry and fresh conditions represented a detectable color change, the R ratio increased from 0.75 to 0.89, the BI index decreased from 209.82 ± 0.62 to 148.38 ± 0.26 and the WI index increased from 24.5 ± 0.11 to 31.8 ± 0.17, indicating color affectations due to the process. The coefficients of determination, (R2) close to 1 and the values closest to 0 of χ2, SSE and RMSE, led to the best fit corresponding to the Weibull distribution model. In addition, it was found that the operation of the drying installation in the hours without incident solar radiation maintained the drying temperature values throughout the process.

Near infrared spectroscopic and aquaphotomic evaluation of the efficiency of solar dehydration processes in pineapple slices

Parallel transformation tests on pineapple slices using two micro drying plants (M1 and M2) operating with solar energy were carried out. Method M1 consisted of an active fan at the top, whose ventilation rate depended on the internal temperature. Method M2 had a continuously working fan at the bottom. The dehydration performance of these two micro-plants was compared by collecting spectra from pineapple slices in reflectance mode (900–1600 nm) at three different times: (0) process start, (1) during the process [48 h] and (2) process end [56 h]. Simultaneously, dry matter, titratable acidity (SH°), pH and aw(water activity) were measured. For these parameters, significant differences ( p < 0.05) were detected between the fresh (t = 0) and the dried product (t = 56). Near infrared (NIR) spectroscopic analysis was carried out according to previously published methods. Spectral data in the wavelength region from 1300 to 1550 nm underwent statistical processing to perform aquaphotomics evaluation and chemometric analysis using PCA (Principal Component Analysis) and LDA (Linear Discriminant Analysis). The aquagrams highlighted differences among fresh, half-dried and dried slices where water molecules were highly organized between the water matrix coordinates C1 to C3 at t = 0 and C2 to C6 for the other evaluated times. The PCA could explain about 98% of the total variance in the PC1–PC3 scores plot. And the additional LDA classified the NIR spectra with an accuracy of 100, 98 and 83% for t = 0, t = 56-M1 and t = 56-M2, respectively. Such preliminary results suggest the applicability of Aquaphotomics and chemometrics for the continuous monitoring of fruit drying processes using an adequate NIR probe. Further experiments are already in progress.

Closed flow solar dehydration with the use of silver nanoparticles: Application for the production of Pouteria lucuma flour

In this research, a closed-flow solar dehydrator with a refrigeration moisture extraction system was evaluated, likewise, the dehydration temperature time was optimized by evaluating three types of heat transfer fluids. The dehydration equipment included devices to absorb thermal energy from incident sunlight, such as a trombe wall and a parabolic cylindrical collector, and a thermo bank system. In addition, the influence of three types of heat transfer fluids (water, oil and oil nanofluid + silver nanoparticles) was evaluated. This dehydration system was applied to process the Pouteria lucuma fruit. The results indicate the reduction of the dehydration time by 58.19% using nanofluid. This treatment prevents the modification of the physicochemical properties of the product and helps preserving its organoleptic properties.