Nanotechnology (packaging films, biocomposites, solar cells)
N. Tajari; H. Sadrnia; F. Hosseini
Abstract
Polylactic acid (PLA) is a thermoplastic, biodegradable, and bioactive polymer obtained from renewable resources such as beets and potatoes. PLA is regarded as a polymer that is nearly brittle, which can restrict its applications in the packaging industry. The mechanical properties of this polymer can ...
Read More
Polylactic acid (PLA) is a thermoplastic, biodegradable, and bioactive polymer obtained from renewable resources such as beets and potatoes. PLA is regarded as a polymer that is nearly brittle, which can restrict its applications in the packaging industry. The mechanical properties of this polymer can be improved by adding nanoparticles and plasticizers. In this research, zinc oxide nanoparticles (1 wt% of PLA), Polyethylene glycol 400 (20 wt% of PLA), and Polysorbate 80 (0.25 wt% of the solution) were used to improve the mechanical properties of PLA films. The effects of these materials on the films were measured at two time points: the first month and the tenth month, with the aim of investigating physical aging, a precursor to polymer degradation. Statistical analysis was performed on the mechanical properties measured during these periods to identify significant differences between the produced films. Results showed that the highest tensile strength (82.99± 1.90 MPa, neat PLA), elongation at break (76.82± 27.22 %, PLA/PEG/ZnO), toughness (20.13± 7.89 J cm-3, PLA/PEG/ZnO), and Young's modulus (2.74± 0.10 GPa, neat PLA) were observed in the first month. Analysis of variance results regarding the effect of time on each film revealed that in most cases, the mechanical properties did not change significantly after ten months. Based on the stress-strain curves, it was found that the neat PLA film is among the resistant materials. The PLA/Polysorbate/ZnO film exhibited brittle behavior in the tenth month. The remaining samples exhibited characteristics that fell between resistant and ductile materials in both the first and tenth months.
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 ...
Read More
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.
M. Porabolghasem; A. Ghazanfari Moghaddam; F. Mozafari ghoraba
Abstract
IntroductionKnowledge of mechanical and viscoelastic properties of agricultural material will be helpful in the transportation and processing of these materials. Giant reed grass, also known as wild cane, is a tall, perennial, bamboo-like, grass that grows in wet areas. The giant reed grass can ...
Read More
IntroductionKnowledge of mechanical and viscoelastic properties of agricultural material will be helpful in the transportation and processing of these materials. Giant reed grass, also known as wild cane, is a tall, perennial, bamboo-like, grass that grows in wet areas. The giant reed grass can flourish in a wide variety of soils, including coarse sands, gravelly soil, heavy clay, and river sediment. This grass attains heights of 7 m and once established the stems can reach a thickness close to 3 cm. The stems of giant reed grass are used for different purposes. Traditionally the stems are used in the villages for fencing, roofing, and producing handcrafts. The modern uses of the giant reed stems include plywood, composites panels and paper production. The giant reed stems are not uniform and are made from many nodes. The number of nodes and the distance between nodes can affect the mechanical properties of the stems. In order to attain a suitable use of the stems in various industries, the physical and mechanical properties of the stems must be determined. Knowledge of mechanical and viscoelastic properties of agricultural material will be helpful in transportation and processing of these materials. The purpose of this research was to determine some relevant mechanical properties of the stems of giant reed grass with different nodes and moisture contents.Materials and MethodsIn this research, different mechanical and viscoelastic tests were performed on the stems of cane at various levels of moisture and number of nodes. The Burger-Voigt model with different number of elements was also used to model the creep behaviors of the stems. The cane stems were cut and divided to three groups of two, four, and six-node stems. The moisture contents of the stems were adjusted to three levels of 30, 40 and 50% (w.b.). After preparing the stems the mechanical tests were performed using an Instron testing machine with a three-point support. The creep tests were done by hanging a 10 kg weight at the middle of each stem. The experiments were done using factorial tests based on completely randomized design. The Young module, toughness, and the yield points of the stems were measured by the three-point method. These parameters were obtained from the stress-strain curves of the three-point compression bending tests. The results showed that the Young module was affected by both moisture and the number of nodes, but there were no interaction effects. The creeps of the stems under 10 kg loading were modeled using 3 to 5 elements Burger-Voigt models. In these models a combination of springs and dashpots are used to represent the stems. The curve fitting was performed using the MATLAB software and the goodness of fitness was verified using the fitted curves and calculating the coefficient of determinations.Results and DiscussionThe results by investigating the graphs and the ANOVA tests showed that the Young module was significantly affected by both moisture and the number of nodes. The obtained Young module for cane stem ranged from 572-1268 MPa. Both yield point and toughness were affected by both moisture and the number of nodes and their values were 65-250 N and 0.016-0.132 J.m-3, respectively. The creep test results indicated that the maximum deformation and maximum time for of the interaction of the two factors was insignificant. The maximum deformations ranged from 2.1-42.5 mm, and the maximum time for reaching the final deformation was 12.5-75 minutes for various moistures and the number of nodes combinations and showed that the 5-element Burger was best for explaining the viscoelastic behavior of cane stems (R2>0.97).ConclusionIn this research, some mechanical properties of the giant reed grass stems were measured and the creep behavior of the stem was modeled using 3-5 elements Burger-Voigt models. The results indicated a decrease in the Young module of the stems with increase with moisture content and increase in the Young module with increase in the number of nodes. On the other hand, the elongation of the stems increased with both number of the nodes and the level of moisture. The 5-element Burger-Voigt model was best fitted to the creep data.
M. H. Aghkhani; M. Baghani
Abstract
The eggshell of birds, as a natural shield and package, protects the tissues inside it from microbial and mechanical damages. Proper intake of calcium, as an important and effective factor in increasing the strength and quality of the eggshell, could reduce complications. In this paper, the effect of ...
Read More
The eggshell of birds, as a natural shield and package, protects the tissues inside it from microbial and mechanical damages. Proper intake of calcium, as an important and effective factor in increasing the strength and quality of the eggshell, could reduce complications. In this paper, the effect of dietary calcium at five different levels on engineering features of Japanese quail eggs in a in their first laying period was investigated. The values for an average of mass, volume, specific mass, shell thickness, major diameter, central diameter and rupture force along the longitudinal and transverse axes were measured. Rupture energy or toughness, slope of the rupture curve (hardness), deformation along the longitudinal and transverse axis to the point of rupture as well as longitudinal and transverse deformation of 450 tested quail eggs (3 period of time, 5 treatment of calcium, 5 replication, 6 observation) were measured. The characters of the specific mass, shell thickness, rupture force, and slope of the rupture curve of quail eggs indicate the strength of quail egg. In this study, variations in all parameters indicating shell strength at different levels of dietary calcium were consistent with each other. Five different treatments with 1.5%, 2%, 2.5%, 3%, and 3.5% calcium content were supplied for the study. By increasing the calcium content of the quail diet from 1.5 to 3 wt%, the volume and weight of quail eggs dropped and shell thickness was reinforced. According to the results, the shell strength of quail eggs along the transverse axis was slightly less than the longitudinal axis, but the flexibility and energy required for quail egg rupture were much greater across the longitudinal axis.
M. Ghasemi; M. Khojastehpour; M. H. Aghkhani
Abstract
Evaluation of mechanical and electrical properties of agricultural products plays an important role in equipment design and optimizing post-harvest operations. Among the crops, tomato and its products are the major processing industries in the world and its economic importance is increasing. Considering ...
Read More
Evaluation of mechanical and electrical properties of agricultural products plays an important role in equipment design and optimizing post-harvest operations. Among the crops, tomato and its products are the major processing industries in the world and its economic importance is increasing. Considering the importance of the quality and various post harvesting uses of tomato, the evaluation of mechanical properties including rupture force and deformation and the work done to establish the rupture of two tomato cultivars (Petoearly CH and Newton) were studied under penetration test based on the electrical conductivity. These properties were measured at three levels of 1, 3 and 5 days after harvesting. The evaluated mechanical properties of both cultivars were decreased by increasing the storage time. Interaction of cultivar and time were significant at the 1% level, for all mechanical parameters except the deformation failure in both cultivars. The electrical conductivity of both cultivars was decreased by increasing the storage time. Interaction of cultivar and time on the electrical conductivity of both cultivars were significant at the 1% level. Significant relationships were found at the 1% level between electrical conductivity and mechanical properties except for deformation of Petoearly CH cultivar. Among the mechanical parameters, rupture forces and rupture works of both cultivars were highly correlated with the electrical conductivity.
S. Kordi; A. Fadavi; M. Eskandari; M. Barari; M. Rafiee; A. Ashraf Mehrabi
Abstract
Mechanical properties of grain are influenced by various factors including soil nutrients and grain moisture content at harvest time. In order to reduce mechanical losses, the design of different processing operations should be performed based on the knowledge of factors influencing the mechanical properties. ...
Read More
Mechanical properties of grain are influenced by various factors including soil nutrients and grain moisture content at harvest time. In order to reduce mechanical losses, the design of different processing operations should be performed based on the knowledge of factors influencing the mechanical properties. The effects of urea fertilization methods and grain moisture content at harvest time on mechanical properties of dried corn were investigated in a field experiment as a strip split plot with four replications based on randomized complete block design at Khorram Abad Agricultural Research Station in 2010. The investigated factors were urea fertilization methods (urea foliar application and urea side-dress application), grain moisture content at harvest time (20, 30 and 40%) and four corn hybrids (NS 640, Konsur 580, Jeta 600 and control SC 704). The moisture content of dried grains due to different absorption property of the treatments was about 7±1 percent. The results showed that the interaction of fertilization methods and hybrid was significant (P < 0.05) for grain toughness. However, the grain moisture content at harvest time had significant effect on all studied traits except on grain firmness. The highest maximum fracture force, displacement at the maximum rupture force, energy consumption at maximum force point, specific deformation, rupture power and toughness were obtained at 20% grain’s moisture content Also, the results showed that NS hybrid had the highest maximum rupture force (219 N), displacement at the maximum fracture force (0.37 mm), energy consumption at maximum force (42.51 mj), rupture power (3.89 . 10-3W) and toughness (0.33 mj mm-3).
K. Hedayati; B. Emadi; M. Khojastehpour; Sh. Beiraghi-Toosi
Abstract
Sugar, which can be extracted from sugar cane and sugar beet, is one of the most important ingredients of food. Conducting more research to increase the extraction efficiency of sugar is necessary due to high production of sugar beet and its numerous processing units in northern Khorasan province. In ...
Read More
Sugar, which can be extracted from sugar cane and sugar beet, is one of the most important ingredients of food. Conducting more research to increase the extraction efficiency of sugar is necessary due to high production of sugar beet and its numerous processing units in northern Khorasan province. In this research, the effect of temperature, time and the frequency of ultrasonic waves on mechanical properties of sugar beet and its extraction rate of sugar in moisture content of 75% were studied. In this regard, an ultrasonic bath in laboratory scale was used. The studied parameters and their levels were frequency in three levels (zero, 25 and 45 KHz), temperature in three levels (25, 50 and 70 ° C) and the imposed time of ultrasonic waves in three levels (10, 20 and 30 min). Samples were prepared using planned experiments and the results were compared with control sugar beet samples. A Saccharimeter was used to measure the concenteration of sugar in samples. Two different types of probe including semi-spherical end and the other one with sharpened edges were used to measure mechanical properties. The studied parameters of frequency, temperature and time showed significant effect on sugar extraction and their resulted effect in optimized levels revealed up to 56% increase in sugar extraction compared with control samples. The obtained values of elastic modulus and shear modulus showed a decreasing trend. The obtained values of total energy of rupture, the total energy of shear, the maximum force of rupture, and the yield point of rupture showed an increasing trend. The frequency had no significant effect on the yield point of rupture and shear force.
E. Velayati; B. Emadi; M. Khojastehpour; M. H. Saeidirad
Abstract
The study of mechanical properties of Berberis not only is useful for design and optimization of transportation, processing and packaging equipment but also can prevent mechanical injuries and losses. In this study force, deformation, energy and toughness were measured at different moisture content levels ...
Read More
The study of mechanical properties of Berberis not only is useful for design and optimization of transportation, processing and packaging equipment but also can prevent mechanical injuries and losses. In this study force, deformation, energy and toughness were measured at different moisture content levels including 70-76, 45-50, 25-30 and 7-10 percent (w.b.). The decrease of moisture content caused increasing rupture force from 1.387 to 2.679 N, decreasing shape deformation from 3.387 to 2.413mm, increasing toughness from 4.297 to 8.220 J/cm3 and decreasing rupture energy from 0.921 to 0.661mJ. Effects of loading speed, force orientation and their interaction were investigated on just fresh Berberis fruit. It was indicated that only force orientation was effective on all investigated properties except toughness. The moisture content was identified as an effective parameter on terminal velocity. It decreased from 9 to 4.5 m/s with decrease of moisture content from 76 to 7 percent (w.b.).
