Nazanin Maryam Mohseni; Habibollah Mirzaee; Masoumeh Moghimi
Abstract
Introduction: Niger seed with scientific name of Guizotia abyssinica Cass from Asteraceae family is a dicotyledonous and one year plant that is one of the main and most important oil sources in Ethiopia and India. In different researches the amount of extracted oil from the seed of this plant has been ...
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Introduction: Niger seed with scientific name of Guizotia abyssinica Cass from Asteraceae family is a dicotyledonous and one year plant that is one of the main and most important oil sources in Ethiopia and India. In different researches the amount of extracted oil from the seed of this plant has been mentioned about 37 to 50 percent. The composition of fatty acid in this plant is similar to safflower and sunflower seed oil (of course with high percentage of Linoleic acid that may reach more than 85 percent). Generally, the mechanical press is one of the most popular methods for extracting oil from vegetable oil seeds all over the world. Increase in temperature will lead to more and faster extraction of oil from seeds and will increase the extraction efficiency. Microwave, is the non-ionized electromagnetic wave with frequency between 300 MHz to 300 GHz and are placed between the radio and infrared waves in the electromagnetic spectrum, consumers’ increasing demand for higher quality products and with minimized waste of nutrients in comparison with conventional thermal methods, caused an increase in use of non-thermal methods such as pulsed electric field methods. In current research it is tried to study the influence of pulsed electric fields and microwave pre-treatments on some characteristics of oil and meals obtained from Niger seed. Materials and methods: To perform this research, the Niger seeds (contain 40% oil) was prepared from local market of Fars Province (Iran). Then the external materials such as weed seeds, sand and stones were separated and removed manually and the seeds were treated with microwave pre-treatment with power of 900W and different procedure times (100 and 200 seconds), and pulsed electric field with two levels of electric field intensities of (250 and 500 kV/cm with 30 pulses). After performing these treatments, the seeds oil was extracted with screw press at the speed of 34 rpm then various experiments, such as the efficiency amount of oil extraction, refractive index, total phenolic compounds, oxidative stability, protein and ash of meals, were performed on the oil in a complete random model with three repetitions. Results and discussions: The comparing group mean test with Duncan’s method indicated that applying pulsed electric fields and microwave pre-treatments in lower times and intensities caused an increase in extraction efficiency. But with increase in the microwave time and also increase in the intensity of pulsed electric field, the efficiency of oil extraction was decreased in such a manner that when a pulsed electric field with intensity of 500 kV/m was used, the oil extraction had the lowest extraction efficiency. The increase of oil extraction efficiency using microwave can be related to more fracture or disintegration of cells which contain oil during treating with microwave. The reason for increase in the efficiency of oil extraction using the pulsed electric fields can be attributed to the electrical decomposition of cells and more permeability of them. A decrease in the oil extraction efficiency with excessive increase in the microwave time and intensity of electric field is probably attributed to more degradation of seeds internal structure and closure of oil outlet duct. Analysis of data obtained from oils refractive index indicated that the pre-treatment type didn’t have any significant influence on the oils refractive index (P>0.05) and the amount of refractive index was 1.478 for all of the measured samples (figure 2). Applying various pre-treatments, caused an increase in the amount of total phenol and oxidative stability of oils in the manner that the maximum amount of total phenol and oxidative stability was obtained from pulsed electric field pre-treatment with the intensity of 500 kV/m. The amount of tocopherol and antioxidant compounds can be the reason for this observation because of applying these pre-treatments. Variance analysis of data obtained from performing tests and experiments indicated that the influence of pre-treatment type on the amount of protein and meals ash was completely significant (P<0.01). Comparison of the means in data obtained from experiments showed that the maximum and minimum amount of protein and meals ash in the treated sample was obtained with 100 seconds microwave and the pulsed electric fields with 500 kV/m intensity, respectively, in other words, applying various treatments (in low times and electric field intensities of microwave and pulsed electric fields) in oil extraction led to an increase in the amount of protein and ash in comparison with non-treated sample and the reason of this fact can be attributed to the more extraction of oil from seeds and consequently an increase in the % protein and ash remained in the meals. Finally, the results of this research indicated that applying microwave (for 100 seconds) and pulsed electric field (with electric field intensity of 250 kV/m) can be very useful in extracting oil from Niger seed because of increase in the extraction efficiency and also increase of useful compounds in oil.
Sara Aghajanzadeh Suraki; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad; Abas Rezaei Asl
Abstract
Introduction: Tomato consumption is recommended due to its brilliant color, amazing taste, high antioxidants and vitamins content. Pectin methylesterase (PME) is known as a pasteurization index in tomato juice. This enzyme plays important roles in cloud stability, color, viscosity and organoleptic properties ...
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Introduction: Tomato consumption is recommended due to its brilliant color, amazing taste, high antioxidants and vitamins content. Pectin methylesterase (PME) is known as a pasteurization index in tomato juice. This enzyme plays important roles in cloud stability, color, viscosity and organoleptic properties of the juice. PME induces the cloud loss in the juice due to the formation of the insoluble calcium pectate; its inactivation is therefore needed to maintain the juice stability. Degradation of ascorbic acid (AA) in the juice is considered as a major challenge during thermal food processing procedures. Furthermore, during its degradation non enzymatic browning occurs, affecting the taste and color. Novel juice processing methods such as infrared (IR) heating and pulsed electric field (PEF) reduce the adverse effects of the conventional thermal method. Quick IR heating produces a juice having higher nutritional value and better quality. During PEF processing, the juice is subjected to high voltage electric pulses for a few microseconds to inactivate target microorganisms and enzymes. Considering the protein structure of the PME, PEF processing at a higher temperature can be effective in this enzyme inactivation. A quick pre-heating of the juice using IR heating was therefore applied in this study. Furthermore, the ohmic heating, occurring during PEF treatment, was not prevented. The synergistic effect of thermal treatment and a non-thermal one (continuous PEF system) on some physicochemical properties of tomato juice were investigated.
Materials and methods: Tomato juice, with an initial temperature of 30℃, was firstly preheated using a continuous IR heating system. During the IR treatment, a temperature controller was applied to set the outlet temperature of the juice to 40, 45 and 50℃. The preheated juice was then passed through a continuous PEF system. The process chamber of the PEF system consists of two parallel stainless steel electrodes with 0.55 mm distance. The length and width of the exposed electrode surface were 10 mm and 0.5 mm, respectively. A square-wave bipolar pulse with a width of 1 ms was selected to perform the treatment within the range of 22.73 to 36.36 kV/cm at 32 Hz. The outlet temperature of the juice was recorded using a data acquisition system during 3.52 s PEF treatment. The treated juice was cooled in an ice-water bath to minimize the effect of cooling period on PME inactivation. AA content, PME activity, cloud value and color of the juice were measured using iodine titration, Kimball, spectroscopy and image processing, respectively.
Results and discussion: Results showed that higher PME inactivation was observed in the juices treated at higher IR pre-heating temperature in combination to higher PEF intensity, resulting in higher cloud stability of the juice. While preheating of the juice decreased the AA content, PEF treatment has no significant effect reflecting the heat sensitivity of this vitamin. Furthermore, color aspects of the juice were more affected by heating treatment in comparison to the PEF processing. Browning index (BI) increased as the AA content decreased. By measuring the total color difference (TCD) it was shown that the PEF had no impact on color properties of the juice. Therefore, the synergistic effect between the IR heating and PEF treatment was also effective in producing the juice having the high nutritional value and better appearance.
