Post-harvest technologies
M. Namjoo; M. Moradi; M. A. Nematollahi; H. Golbakhshi
Abstract
In this study, the air drying of cumin seeds was boosted by cold plasma pre-treatment (CPt) followed by high-power ultrasound waves (USp). To examine the impact of included effects, different CP exposure times (0, 15, and 30 s), sonication powers (0, 60, 120, and 180 W), and drying air temperatures (30, ...
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In this study, the air drying of cumin seeds was boosted by cold plasma pre-treatment (CPt) followed by high-power ultrasound waves (USp). To examine the impact of included effects, different CP exposure times (0, 15, and 30 s), sonication powers (0, 60, 120, and 180 W), and drying air temperatures (30, 35, and 40 ºC) were selected as input variables. A series of well-designed experiments were conducted to evaluate drying time, effective moisture diffusivity, and energy consumption, as well as color change and rupture force of dried seeds for each drying program. Numerical investigations can effectively bypass the challenges associated with experimental analysis. Therefore, the wavelet-based neural network (WNN), the multilayer perceptron neural network (MLPNN), and the radial-basis function neural network (RBFNN), as three well-known artificial neural networks models, were used to map the inputs and output data and the results were compared with the Multiple Quadratic Regression (MQR) analysis. According to the results, the WNN model with an average correlation coefficient of R2 > 0.92 for the train data set, and R2 > 0.83 for the test data set provided the most beneficial tool for evaluating the drying process of cumin seeds.
Post-harvest technologies
A. Khalaj; E. Ahmadi; S. Mirzaei; F. Ghaemizadeh; R. Abbaszadeh
Abstract
IntroductionGrape is a major horticultural crop with a high nutritional value in the world. The optimal geographic and climatic conditions in Iran have positioned it as one of the most important regions for grape cultivation in the world. Black rot, caused by Aspergillus niger, is a highly destructive ...
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IntroductionGrape is a major horticultural crop with a high nutritional value in the world. The optimal geographic and climatic conditions in Iran have positioned it as one of the most important regions for grape cultivation in the world. Black rot, caused by Aspergillus niger, is a highly destructive fungal disease that affects the grapes by targeting wounded areas. It causes crushing of the grapes, the falling of berries, and reduces transportation and storage properties (Ponsone et al., 2011). Various methods, such as fumigating bunches with sulfur dioxide and storing them in a modified atmosphere, have been used to control fungal rot and prolong the shelf life of grapes. However, each method has its limitations. Grape fumigation with sulfur gas is harmful to human health (Duarte-Sierra et al., 2016) and the efficiency of modified atmospheric storage on rot control and maintaining the quality of grapes depends on the type of variety, storage temperature, and especially gas concentration (Himelrick, 2003).Given the lack of efficiency in traditional methods, it is imperative to introduce modern techniques that can effectively disinfect microorganisms. These advanced methods offer several advantages, including the preservation of crop quality, an increase in crop shelf life, the promotion of good health, and substantial economic benefits. A technique of this type includes using non-thermal (cold) plasma (NTP) technology to eliminate food microorganisms (Bourke et al., 2018). The effect of cold plasma at atmospheric pressure on the reduction of bacterial populations in food products such as lettuce, tomato, strawberry, and cherry tomato has been reported (Bermúdez-Aguirre et al., 2013; Pasquali et al., 2016; Ziuzina et al., 2014). Research has shown that cold plasma can effectively inactivate Aspergillus in various orchard and agricultural products (Butscher et al., 2016; Ghorashi et al., 2020; Selcuk et al., 2008). The effect of cold plasma on the quality characteristics of the product during the post-harvest period has also been investigated. Blueberries treated with cold plasma for less than 15 minutes showed remarkable results: after 10 days, the fruit exhibited reduced lipid peroxidation and darkening, with no impact on the total anthocyanin content, pH, or firmness of the product (Hu et al., 2021). In a study by Rana et al. (2020), it was found that subjecting strawberries to 15 minutes of cold plasma with packaging after 5 days of storage at 25°C had no significant impact on pH, TSS, and moisture content of the fruit.The review of the literature reveals the absence of research on fungal disease control and grape quality evaluation following the use of NTP. This study aims to investigate the efficiency of plasma treatment in reducing the infection with Aspergillus fungi, along with examining the physical, chemical, and mechanical properties of Fakhri grape.Materials and MethodsThis research was conducted as a completely randomized design in a factorial experiment at four plasma levels (0, 10, 20, and 40 s) and five storage periods (1, 2, 3, 4, and 5 weeks) with three replications at 4°C. A plasma generator was first designed and manufactured in this study. A specifically designed and fabricated plasma application probe was also developed for grape berries. The individual grape berries were then sterilized with 1% sodium hypochlorite under a laminar hood for 2 minutes. Afterward, they were rinsed three times with sterile distilled water to remove any remaining disinfectant residue from their surfaces. Sterilized berries were immersed in Aspergillus spore suspension with 105 spores.ml-1 concentration. Finally, all samples were dried on paper filters and prepared for different plasma treatment durations (0, 10, 20, and 40 s). The treated samples were stored at 4°C, and the infection percentage and microbial load were measured on a weekly basis. To assess the preservation quality, chemical parameters such as pH, TSS, and TA, physical parameters (color change and weight loss), and mechanical properties were measured every week. Additionally, thermal imaging was performed weekly.Results and DiscussionPlasma application during storage significantly reduced the infection percentage and microbial load in Aspergillus-inoculated samples. At the end of the storage period, the infection percentage and microbial load in the 40-second plasma treatment were 5% and 2.5 CFU g-1 respectively, while in the control group, the infection percentage was 100% and the microbial load was 4 CFU g-1. At the end of the storage period, the lowest pH level in the plasma was observed for 40 s plasma. This could be attributed to effective contamination control, as fungal contamination leads to alkalization of the environment. The highest amount of TSS was also observed in control and 40 s plasma. But in the 10 and 20 s plasma treatment, the process of changes was gradual and not significant. The higher TSS level of control and 40 s plasma can be due to the weight loss caused by the spread of contamination and moisture leakage caused by damage to the tissue. This decrease in moisture leads to an apparent increase in the TSS index. Research has shown that plasma primarily affects the surface characteristics of products, and when applied with the appropriate voltage and duration, it does not alter the internal chemical properties (Hu et al., 2021). Over time, weight loss increased in all treatments. This increasing trend during the storage period is higher in control and 40 s plasma compared to 10 and 20 s plasma. Therefore, the weight loss in the control can be due to the spread of contamination and aging of the product over time. However, the weight loss in the 40-second plasma treatment can be due to the destruction of the fruit tissue caused by longer duration of the plasma application.In the current research, by increasing the duration of plasma application to 40 s, a significant decrease in L*, a*, and b* indices and an overall change in the color of the product was observed. Research shows that in blueberries, inappropriate duration of plasma treatment causes the loss of wax on the fruit surface and leads to darkening of the product (Hu et al., 2021). The highest and lowest changes in temperature drop were observed in the control treatment (5°C) and 10 and 20 s plasma (3 and 3.5°C, respectively). According to research, an increase in fungal contamination leads to a decrease in humidity, increases weight loss, and subsequently a decrease in product temperature. A decline in mechanical characteristics was noted for the control and plasma treated samples during the storage period. The lowest value for indicators was observed in the 40 s plasma treatment. However, no significant difference was observed in samples treated with plasma for less than 20 seconds compared to the control group up to the middle of the storage period. According to a report by Misra et al. (2014), plasma application can reduce tissue softness. Therefore, optimizing its plasma duration and intensity is very important (Pan et al., 2021). ConclusionOur experiments aimed to investigate the effect of NTP treatment on controlling Aspergillus infections while preserving the quality properties of Fakhri grapes. The obtained results are important for two main reasons. Firstly, an innovative probe was designed for plasma applications, specifically tailored to the shape and size of individual grapes in order to thoroughly cover them with plasma. Secondly, application of plasma was carried out for the first time and yielded valuable results, indicating that this technique can control fungal infections and preserve the chemical, physical, and mechanical properties of grapes.
Post-harvest technologies
M. Pourbagher; R. Pourbagher; M. H. Abbaspour-Fard
Abstract
Today, almost half of the total human food, especially in Asia, is directly supplied from grains, and nearly 70% of the cultivated area of the world, which is one billion hectares, is used for growing grains. Therefore, non-destructive methods must be found and developed to increase seed quality in agriculture ...
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Today, almost half of the total human food, especially in Asia, is directly supplied from grains, and nearly 70% of the cultivated area of the world, which is one billion hectares, is used for growing grains. Therefore, non-destructive methods must be found and developed to increase seed quality in agriculture and industry. Cold plasma is a novel and efficient method that can be used in the agricultural and food sectors for the inactivation of surface microorganisms and the excitation of seeds. This review presents a summary of the effectiveness of cold plasma treatment on the characteristics of four important cereal plants: wheat, rice, corn, and barley. The focus is on the effects of this treatment on seed germination, surface property changes, water uptake of seeds, growth parameters of root, shoot, and seedling length, biomass parameters, and metabolic activities. By examining the research conducted by the researchers, it can be seen that the cereal seeds treated with cold plasma had better germination power, water absorption, shoot length, growth efficiency, shoot and root weight, and metabolic activity. This review can provide insight into the promising trends in utilizing plasma as a method to decrease the prevalence of harmful plant diseases transmitted through seeds and reduce the dormancy of hard seeds.
M. Fereydoni; H. Haji Agha Alizaheh
Abstract
IntroductionAs the world's population grows, more food need to be produced. Plasma technology is one of the methods that can improve plant growth. Cold plasma is effective in increasing growth and germination indices. In this article, the effect of cold plasma based on corona discharge was investigated ...
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IntroductionAs the world's population grows, more food need to be produced. Plasma technology is one of the methods that can improve plant growth. Cold plasma is effective in increasing growth and germination indices. In this article, the effect of cold plasma based on corona discharge was investigated on germination of Adel, Mansur, and Azad chickpea varieties.Materials and MethodsIn the corona discharge method, a relative vacuum should be used. Corona discharge is formed when there are pronounced spatial in-homogeneities in the electric field, in particular, when the electric field exceeds the breakdown threshold in a limited spatial region. This commonly occurs when highly asymmetric electrodes are employed, such as a point and a plane. Thermodynamically corona is a very non-equilibrium process, creating a non-thermal plasma. The avalanche mechanism does not release enough energy to heat the gas in the corona region generally and ionize it, as occurs in an electric arc or spark. Only a small number of gas molecules take part in the electron avalanches and are ionized, having energies close to the ionization energy of 1- 3 ev, the rest of the surrounding gas is close to ambient temperature. Corona discharge is a weakly ionized non-equilibrium plasma based on the avalanche mechanism. If it reaches a close distance with a conductive material or increase the electrical field, it can create longer breakdown streamers and eventually create sparks. The system is designed to convert 220V voltage with a frequency of 50 Hz to 12 kV voltage with a frequency of 9 kHz. Two electrodes with a 2 cm distance are in a vacuum chamber with a negative pressure of 20 pounds per square inch. And the samples are placed between two electrodes. Experiment was performed in form of a.factorial experimental design based on a CRD. In this plan, treatments are randomly placed in experimental units. The type of factorial experiment performed is 3×3×2×2 and multiplied numbers are factor levels. Seed production year factor in two levels, moisture factor in two levels, Seed variety factor in three levels, and exposure duration factor in three levels were examined. Plasma-exposed seeds and non-exposed seeds were grown under the same conditions. The samples were selected completely randomly. The samples were wetted 24 hours before exposure. Then all 18 chickpeas were placed in a dish in order to observe proper repetition. Samples from each dish were exposed to cold plasma under the same conditions between samples for a specified period of time. After exposing the samples to cold plasma, samples of all dishes under the same conditions at 30 °C and 300 lux environmental light were examined for germination evaluation. For this purpose, samples of each dish were placed in a cover of cotton cloth. They got wet every 4 hours. After 48 hours, all samples were examined and the root length of each sample was measured.Results and DiscussionThe results showed that seeds exposed to plasma for 60 seconds had a faster germination speed than those without exposure. Also, seeds that were exposed to plasma for 30 seconds had a longer root length than those without exposure. According to the results of statistical analysis, exposure to cold plasma for 30 seconds has increased root length in Adel chickpea variety up to 12.5% and in Mansour variety up to 18%.ConclusionAfter statistical analysis, appear that root length under the same conditions, during 30 seconds of exposure to cold plasma, is significant at 5% level from non-exposure and 60 seconds of exposure. Microscopic images of samples were examined on the outer surface and inner tissue of seed cell. Studies have shown that the outer surfaces of seeds exposed to cold plasma are smoother, less prominent and smaller contact angle than those without exposure to plasma. This change can increase the hydrophilicity of seeds. But cold plasma had no effect on cell tissue in terms of size and number.
