Drying Of Pepper Research Articles

Drying of red pepper slices in a solar greenhouse dryer and under open sun: Experimental and mathematical investigations

Abstract The present work is mainly focused on the study of the solar drying of red pepper grown in the North of Tunisia. A new mixed mode solar greenhouse dryer (SGD) with forced convection was used in the drying experiments. To further understand the characteristics of the SGD, an open sun drying experiment was conducted under the same climatic condition. The results show that the constant rate period is absent from the experimental drying curves. The experimental drying curves show only the falling rate period. Thus, the drying time which was three days in the open sun decreased to two days in the SGD. The drying data were fitted to eight different mathematical models. The fit quality of the proposed models was evaluated by using the coefficient determination (R2), reduced chi-square (χ2) and root means square error (RMSE). Among the models, Modified Henderson and Pabis model for the forced solar drying and the open sun drying was found to best explain the thin-layer drying behaviour of pepper slices. The instantaneous thermal efficiency of the solar collector varied between 30% and 80%, at a mass flow rate of 0.047 kg/s. The overall energy efficiency of the solar dryer was 34%. Finally an economic evaluation was calculated using the criterion of payback period which was found very small 1.02 years compared to the life of the dryer (SGD) 20 years.

Hydrodynamics investigation of pepper drying in a swirling fluidized bed dryer with multiple-group twisted tape swirl generators

The present work aims to investigation the behavior of drying peppers in a swirling fluidized bed dryer (S-FBD) fitted with multiple twisted tape swirl generators. A multiple-group twisted tape swirl generator was located at the air inlet at the bottom of the bed. The effects of the superficial air velocity (U*=U/Umf = 1.0, 1.1 and 1.2) on the moisture content (MC), moisture content ratio (MR) and drying rate (DR) were examined. The experimental results showed that the S-FBD can reduce the moisture content of peppers more rapidly than a conventional fluidized bed dryer (FBD). The S-FBD gave a higher DR and decreased drying time compared to that of a FBD. The results also indicated that operation at higher superficial air velocities resulted in a greater DR, especially at the beginning stage of the drying process. For the S-FBD, the reduced of MC, MR and DR at a high superficial air velocity (U*=U/Umf = 1.2) was better than at low superficial air velocities (U* = 1.0 and 1.1). Furthermore, five different drying models were evaluated to predict the performance of the S-FBD.

Modelling of vacuum drying of cherry pepper

Drying is a complex phenomenon and study of drying kinetics and modelling is very important for describing the moisture movement with respect to time and predicting the dryer performance. Considering this fact, vacuum drying characteristics of cherry pepper was studied at different drying temperatures (50, 60 and 70oC). Cherry pepper were dried from initial moisture content of about 400% (dry basis) to 13 – 14.5% (dry basis) at different temperatures at 630 mm Hg vacuum. Time required to dry cherry peppers at 50, 60 and 70p C plate temperatures were 19 h, 9.75 h and 8 h respectively. Moisture reduction of cherry pepper at various temperatures was modelled using thin-layer models viz. Lewis, Page, Modified Page and Henderson and Pabis model. Based on highest value of coefficient of determination, lowest values of reduced chi square and root mean square error, Modified Page model was found to be the best fit. Moisture diffusivity increased from 6.27 × 10-10 to 1.9× 10-9m2s-1 as plate temperature increased from 50 – 70oC. Activation energy was estimated to be 50.98 kJkgmol-1.

Prediction of Mathematical Models of the Drying Kinetics and Physicochemical Quality of the Chili Pepper

The present work had as objective to determine the kinetics of drying of the chili pepper, to adjust different mathematical models to the experimental values as a function of the water content and to characterize the same in it’s in natura form and after the drying in the temperatures of 60, 70 and 80 °C. The samples were weighted periodically until reaching the equilibrium. The mathematical models of Wang and Singh, Henderson and Pabis, Newton, Page and Thompson were adjusted to the experimental data. The best adjustment was determined in relation to the highest values of the coefficient of determination (R2) and Mean Square Deviation (MSD). The obtained results showed that the drying of the pepper is influenced by the temperature of the drying air. It is concluded that the model of Henderson and Pabis was the one that best fit to the experimental data. The increase of the drying temperature promoted a reduction in the time required for the peppers to reach the moisture of the hygroscopic balance. The parameters of acidity, lipids and proteins remained close at the different drying temperatures used, however higher when compared to the samples in natura. It can be noticed that ashes and vitamin C have suffered considerable decrease as the temperature increased, as a result of the chemical transformations that occurred in the peppers due to heat exposure and loss of moisture.

Cold plasma pretreatment enhances drying kinetics and quality attributes of chili pepper (Capsicum annuum L.)

Chili pepper is difficult to dry as the outermost surface is covered with an epicuticular wax layer, which hinders moisture transfer. Chemical dipping pretreatments and thermal blanching methods are often employed to enhance its drying process. However, chemical pretreatments hold the issues of chemical additives residue and thermal blanching methods tend to result in a high loss of bioactive compounds. Cold plasma is an ionized gas that contains different electrons, ions, and reactive neutral species. In current work, the feasibility of cold plasma as a non-thermal pretreatment technology for chili pepper drying is explored. The effects of different cold plasma pretreatment time (15, 30, 45, 60 s) on hot air drying kinetics and quality attributes of chili pepper, such as colour, red pigment retention, antioxidant activity, and microstructure were investigated. Results indicate that cold plasma can enhance the drying rate and the exposure time of 30 s achieves the optimum result. Microstructure observations show the existence of micro-holes, which explain how plasma treatment can enhance the drying kinetics. Quality attributes showed that the colour parameters had no significant changes under various treatment times. The retention of red pigment content was improved by plasma treatment of 30 s, whereas longer exposure times had a negative effect. The antioxidant activity of samples increased with the increase of cold plasma exposure time. Results indicate that cold plasma is a promising pretreatment technology for chili peppers as it enhances drying kinetics and quality attributes of chili pepper.

Thermal Degradation Kinetics of Capsaicin on Blanching-Brine-Calcium Pretreatment Red Chili Pepper Drying

Post-harvest red chili pepper (Capsicum frutescens) has highly capsaicin as bioactive compound and moisture content. However, capsaicin is the responsible bioactive compound in chili for hot sensation that easy to degrade by partial oxidation caused introduction of heat in drying process. The objective of this research was to investigate kinetics of capsaicin degradation in the drying process under blanching-brine-calcium pretreatment and various temperatures. For this purposes, chili provided local farmer was pretreated using blanching-brine-calcium pretreatment. Afterward, they were dried at 40, 50, 60, and 70 oC for 8 hours. Degradation of capsaicin content was observed every 2 hours using Thin Layer Chromatography (TLC). Results showed kinetics of capsaicin degradation was categorized as second order reaction. At the same temperature and time, capsaicin retention of blanching-brine-calcium pretreated chili has highest value. The temperature dependence of the capsaicin degradation rate was analyzed using Arrhenius correlation. The activation energy for degradation rate of capsaicin during drying was around 45.10367 kJ/mol.K. It indicated the degradation rate increased as well as increased the temperature at the same time.

Kinetics and Mathematical Modeling of Microwave Drying of Sri Lankan Black Pepper (Piper nigrum)

Drying characteristics of black pepper (Piper nigrum) was investigated in a microwave drying system. Drying experiments were carried out at three different microwave power levels, 180, 360 and 540 W and the moisture content was measured at different time intervals. Experimental results were fitted to seven thin layer drying models; Newton, Page, Henderson and Pabis, Logarithmic, Midilli et. al., Weibull and Kaleta et. al.. Statistical indicators; Coefficient of determination (R2), Root mean square error (RMSE) and reduced chi square values (c2) showed Midilli et. al., Weibull and Kaleta et. al. models give better fit to the experimental values. Drying rate constants and the equation constants were compared and analyzed. Similarities of the drying models were observed and discussed with respect to the equation parameters. The absence of the constant drying rate period in drying curves show the drying of black pepper lies totally in the falling rate period where the drying rate is controlled by the moisture diffusion. Maximum drying rates observed were 0.02, 0.05 and 0.08 kg moisture/kg of dry material/ min at 180, 360 and 540 W power levels. Results revealed drying rate constant and the effective moisture diffusivity values increases with the microwave power level. Drying rate constants were 0.03, 0.09 and 0.16 min-1 and the effective moisture diffusivity values were 2.43 x 10-10, 4.87 x 10-10, 1.42 x 10-9 m2/s for power levels of 180, 360 and 540 W respectively. The Activation energy of black pepper calculated based on the Arrhenius equation is 86.7 W/g.

The effect of ultrasound-assisted vacuum drying on the drying rate and quality of red peppers

Ultrasound-assisted vacuum (USV) drying is a promising method to increase heat and mass transfer rate. This study aimed to examine effects of USV drying on the drying rate and some quality parameters of red peppers at 45, 55, 65, and 75 °C. The results were compared with USV control drying (vacuum drying without ultrasound treatment) and the other drying methods. The USV drying shortened the drying period to 25% and increased the effective moisture diffusivity (Deff) to 89% when compared by USV control drying. The dehydration kinetics of the red peppers were successfully described using seven thin layer drying models for all of the dehydration methods, and the logarithmic model had the best fit for the USV drying, with highest R 2 and lowest RMSE values. The total yeast and mold counts were significantly reduced following the USV drying in comparison with the USV control drying. This study suggested that USV drying could be used effectively in drying of red pepper with high drying rate and no significant bioactive compound degradation compared to USV control.

Analysis the Results of Control and Elimination of Coal-Burning-Borne Endemic Fluorosis in Chongqing City

Objective: Discuss the analysis of the results of control and elimination of coal-burning fluorosis in Chongqing, and evaluate the effect of prevention and control. Methods: Dean’s method was used to investigate the fluorosis for the local children whose ages ranged from 8 to 12 years old, the use of improved stoves in residential households, the drying of corn and pepper for human consumption, and the results were evaluated and discussed according to the national standard for the control and elimination of coal-burning fluorosis. Results: The prevalence rate of dental fluorosis borne-disease in children whose ages ranged from 8 to 12 years old was about 11.28% in 661 historically diseased villages in 100 townships and in 13 districts and counties of Chongqing city. The correct utilization rates of improved stoves, qualified improved stoves, and qualified stoves were 100%, 98.82%, and 99.45%, respectively. The correct drying rates of corn and pepper for human consumption were 99.88% and 99.75% respectively. There are 24 uncontrolled villages, 225 controlled villages, and 412 villages in eliminated disease zones in administrative villages. There are 4 villages and counties in uncontrolled, 4 in controlled, and 5 eliminated areas in districts and counties. Conclusion: Fluorosis borne-disease caused by coal-burning in Chongqing has reached the control and elimination targets of the twelfth Five-year plan.

Effect of blanching-brine-calcium pretreatment on red chili pepper drying

The red chili pepper drying aims to remove moisture content up to 11% (wet basis). Dried chilies can be easy to distribute and have longer shelf life because it can be protected from decaying by enzymatic and microbial activity. Pretreatment in drying is one of alternative to decrease drying time. This present study was carried out on effect of blanching-brine-calcium pretreatment toward drying kinetics in chili. In this case, chili provided from the local market was pretreated with blanching, dehydrated osmotic with brine, calcium dipping pretreatment and combination of them. The chili products were dried in tray dryer at 40°C, 50°C, 60°C and 70°C for 8 hours afterward. Result showed that Lewis model is suitable drying model. The blanching-brine-calcium pretreated chili can be well and faster dried with activation energy was 36.4290 kJ/mol and k0 was 7.8712. At 70°C, red chili pepper needed 6.467 hours todry. Thus, the blanching-brine-calcium pretreatment can be potential to reduce the energy cost for drying as well as retain the quality.

Degradation rate of vitamin B6 on red chili pepper drying by blanching-brine-calcium pretreatment

Drying is one of the alternatives to prevent spoilage in red chili pepper by removing moisture content. Red chili pepper (Capsicum frutescens) has complex nutrition components such as vitamins and bioactive compound. However, vitamin B6 content in chili can degrade significantly in drying process by heat. This research studied degradation rate of vitamin B6 in chili drying process under various pretreatments and temperatures. In this study, post-harvest chili before dried was pretreated by blanching, osmotic dehydration with brine, immersing in calcium chloride solution and the combination of all them. They were dried in tray dyer at various temperatures 40°C, 50°C, 60°C and 70°C. Degradation of vitamin B6 content was analyzed every 2 hours by High-Performance Liquid Chromatography for 8 hours. Results showed that blanching-brine-calcium pretreatment was expected to reduce drying time and retain high content of vitamin B6 in red chili pepper. The degradation rate of vitamin B6 in chili followed second-order reaction. The degradation rate was influenced by temperature change referring to Arrhenius equation with activation energy was about 31.97 kJ/ mol K and constant rate (k0) was 3.769. Therefore, the vitamin B6 retention can be estimated at various pretreatments, times and temperatures. Furthermore, the favorable drying conditions can be evaluated.

Red pepper (Capsicum annuum L.) drying: Effects of different drying methods on drying kinetics, physicochemical properties, antioxidant capacity, and microstructure

ABSTRACTResults of an experimental study are presented and discussed for pulsed vacuum drying (PVD), infrared-assisted hot air-drying (IR-HAD), and hot air-drying (HAD) on drying kinetics, physicochemical properties (surface color, nonenzyme browning index, red pigments, rehydration ratio, water holding capacity, and ascorbic acid), antioxidant capacity (ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity), and microstructure of red pepper. As expected, the drying time decreased with an increase in drying air temperature, IR-HAD needed the shortest drying time, followed by HAD and PVD. The effective moisture diffusivity (Deff) of red pepper under PVD, HAD, and IR-HAD was computed to be in the range 1.33–5.83 × 10−10, 1.38–6.87 × 10−10, and 1.75–8.97 × 10−10 m2/s, respectively. PVD provided superior physicochemical properties of dried red pepper compared to samples dried by HAD and IR-HAD. In detail, PVD yielded higher rehydration ratio, water holding capacity, red pigment and ascorbic acid content, brighter color, lower nonenzyme browning index, and comparable antioxidant capacity compared to samples dried by HAD and IR-HAD at the same drying temperature. Furthermore, PVD promoted the formation of a more porous structure, while HAD and IR-HAD yielded less porous structure. The current findings indicate that PVD drying has the potential to produce high-quality dried red pepper on commercial scale.

Hydrodynamics study on drying of pepper in swirling fluidized bed dryer (SFBD)

Malaysia is one of the pepper producer with exports quantity reaching more than 90000 tonnes between 2010 until 2016. Drying of pepper is mandatory before their export and at present, pepper was dried by sun drying to reduce cost. This conventional drying method was time consuming and may take four days during rainy season, which retards the production of pepper. This paper proposes the swirling fluidized bed drying (SFBD) method, which was known to have high mixing ability and improved solid-gas contact to shorten the drying time of products. A lab scale SFBD system was constructed to carry out this study. Hydrodynamic study was conducted for three beds loadings of 1.0 kg, 1.4 kg at a drying temperature of 90°C. The SFBD has shown excellent potential to dry the pepper with a relatively short drying time compared to the conventional method. Batch drying for the bed loads studied only took 3 hours of drying time only. It was found that bed higher bed loading of wet pepper requires longer drying time due to higher amount of moisture content in the bed. Four distinct regimes of operation were found during drying in the SFBD and these regimes offer flexibility of operation. The total bed pressure drop was relatively low during drying.

Modeling and simulated design: A novel model and software of a solar-biomass hybrid dryer

Solar-biomass hybrid dryers are widely used as environmentally friendly alternatives to fossil fuel dryers for the preservation of agricultural food products. However, the design and optimization of hybrid dryers often involve construction of expensive prototype systems and time-consuming studies. This study presents a novel hybrid dryer model and a dryer design and simulation software, which can be used to improve hybrid dryer design efficiency. The methodologies adopted are those of functional analysis, mathematical modeling and virtual prototyping, with SolidWorks employed for CAD modeling, and Matlab for numerical simulations and implementation of mathematical models into a user interface. The software package has as main functions (a) dimensioning the hybrid dryer, which comprises a solar collector, combustion reactor and tunnel drying chamber, (b) cost analysis and financial appraisal, and (c) temperature dynamic simulation in the system. The novel software has been successfully employed to dimension a hybrid dryer for drying of green pepper.

Modelling the Drying Characteristics and Kinetics of Hot Air-Drying of Unblanched Whole Red Pepper and Blanched Bitter Leaf Slices

The objective of this study was to investigate the drying characteristics and kinetics of red pepper and bitter leaf under the influence of different drying temperatures. The drying experiments were carried out at dry bulb temperature of 35, 45, 55 and 75oC, respectively in an oven dryer. The results showed that as drying temperature increased, drying rate also increased and the drying time decreased. It was observed that un-sliced red pepper and sliced bitter leaf would dry within 2.5-12 h and 1.67-7 h, respectively at temperature ranging from 75 to 35oC. The drying of red pepper and bitter leaf was both in the constant and falling rate period. Four semi-empirical mathematical drying models (Newton, Page, Henderson and Pabis, and Logarithmic models) were fitted to the experimental drying curves. The models were compared using the coefficient of determination (R^2) and the root mean square error (RMSE). The Page model has shown a better fit to the experimental drying data of red pepper and bitter leaf, respectively as relatively compared to other tested models. Moisture transport during drying was described by the application of Fick’s diffusion model and the effective moisture diffusivity was estimated. The value ranges from 15.69 to 84.79 × 10-9 m2/s and 0.294 to 1.263 × 10-9 m2/s for red pepper and bitter leaf, respectively. The Arrhenius-type relationship describes the temperature dependence of effective moisture diffusivity and was determined to be 37.11 kJ/mol and 32.86 kJ/mol for red pepper and bitter leaf, respectively. A correlation between the drying time and the heat transfer area was also developed.

Effect of high-humidity hot air impingement blanching (HHAIB) on drying and quality of red pepper (Capsicum annuum L.).

Effects of high-humidity hot air impingement blanching (HHAIB) under different times (30, 60, 90, 120, 150, 180, 210, and 240s) on drying characteristics and quality attributes of red peppers in terms of surface colour, red pigment content, microstructure and texture were investigated. Results showed that polyphenol oxidase (PPO) residual activity of the samples decreased with increasing blanching time; it was decreased to 7% after 120s. A first-order fraction model described PPO inactivation well. Suitable HHAIB time can reduce drying time extensively. Pepper surface colour was influenced by different treatments. In terms of red pigment content, there was no significant difference for blanching time under 120s, whereas over blanching (blanching time ⩾150s) can significantly reduce the red pigment content. Microstructure observations indicate that superficial micro-cracks occur, which explain, why HHAIB enhances drying rate. The firmness, hardness, and gumminess of the samples decreased with increase of HHAIB time.

Drying of chilli pepper in various conditions

Fresh red pepper was blanched with water (at 90 °C for 3 min), 5% potassium carbonate and 2% ethyl oleate (both at 20 °C for 1 min) and then dried either with forced hot air (at 55, 65 and 75 °C) or solar energy. Then the effects of different variables on the kinetics and quality parameters of dehydrated red chilli pepper were studied. The peppers blanched with boiling water or ethyl oleate and dried at 75 °C had the lowest drying time and their quality indicators (vitamin C, colour values, shrinkage percentage, and rehydration rate) were not significantly different. However, peppers blanched with potassium carbonate and dried at 55 °C had the highest content of this vitamin and also colour scores among different treatments. While the untreated samples (blank) dehydrated either with hot air at 55 °C or solar energy had the lowest shrinkage (%), they did not have significant difference (P<0.01) with the water-blanched samples dried at 65 °C.

Microwave- and infrared-assisted convective drying of green pepper: Quality and energy considerations

This article presents the results of combined convective-, microwave- and infrared drying of green pepper. Five drying programs with different application of microwave and infrared radiation were used to dehydrate this biomaterial. The pure convective drying was a reference test. The aim of the study was to analyze the effect of hybrid drying on drying kinetics, energy consumption and quality of the product. The quality of the dried bioproduct was assessed based on the vitamin C retention, water activity, total color change and the ability to rehydration. The experiments proved that convective drying assisted with both microwave and/or infrared radiation significantly shortened the drying time, allowed better preservation of vitamin C content, improved the color of the product, and saved energy consumption compared to pure convective drying.

Drying of seeds through oscillating infrared heating

ABSTRACTOscillating infrared (IR) drying of onion, white mustard, sweet pepper, and wheat seeds as well as the effect of this drying method on the seeds’ stimulation have been studied. It was found that oscillating IR drying was highly advantageous for onion seeds which possess the lowest germination degree and germination energy. The influence of initial moisture content of the onion seeds, the duration of the oscillating IR drying, and the processing temperature on the stimulation effect have been established. The most favorable stimulation temperature was determined. It was shown that this stimulation effect holds unchanged for at least eight months. A mathematical model for drying kinetics based on the solution of the mass conductivity equation was proposed and the method of the process engineering calculation has been developed and validated for onion and mustard seeds. The necessary experimental data on mass conductivity and concentration equilibrium for onions and mustard seeds have been obtained.

Influência das características do ar na cinética de secagem de pimenta variedade bico

ResumoA pimenta bico, pertencente à espécie Capsicum chinense, é muito utilizada na culinária brasileira no preparo de diversos pratos e também em conservas. Por se tratar de um alimento altamente perecível, faz-se necessária a utilização de métodos para a sua conservação, destacando-se o processo de secagem. O presente trabalho teve como objetivo determinar e analisar a cinética de secagem da pimenta bico em diferentes condições de temperatura e velocidade do ar de secagem. A pimenta foi submetida ao processo de secagem por meio de um secador de bandejas em camada delgada, com velocidade do ar de secagem controlada a 1,0; 1,5 e 2,0 m/s e temperatura de 40, 50 e 60 °C. As pimentas foram colocadas no interior do equipamento em bandejas removíveis de aço inoxidável e as amostras, pesadas periodicamente até o equilíbrio ser atingindo. Os modelos matemáticos de Page, Henderson e Pabis, Midilli e Kucuk, Thompson e Aproximação da difusão foram ajustados aos dados experimentais. O melhor ajuste foi determinado em função dos maiores valores do coeficiente de determinação (R2), menores valores de desvio médio relativo (P) e do erro médio estimado (SE). Os resultados obtidos mostraram que a secagem da pimenta é influenciada pela velocidade e temperatura do ar de secagem, visto que quanto maior a temperatura do ar de secagem, mais rapidamente obtém-se o equilíbrio de umidade das amostras. O modelo de Midilli e Kucuk foi o que se ajustou melhor aos dados experimentais. Os valores de difusividade efetiva encontrados variam de 1,65 × 10–10 a 5,01 × 10–10 m2/s e a energia de ativação varia de 98,42 a 108,13 kJ/mol.