جستجوی مقالات مرتبط با کلیدواژه « امواج فراصوت » در نشریات گروه « مکانیزاسیون کشاورزی »

These days, most of the disinfectants used in the food industry such as chlorinated compounds are dangerous and harmful. Common methods of removing all types of pollution have many disadvantages for human health and the environment. It is possible to help preserve the environment and human health by replacing these methods with new ones such as ultrasound technology. Ultrasonic waves are non-thermal technology that helps increase microbial safety and prolong the shelf life of heat-sensitive foods with nutritional value and functional characteristics. Ultrasonic waves are known as one of the most effective disinfection methods for all forms of microbial and fungal contamination. These waves reduce the resistance of microorganisms by physically damaging them. Therefore, this study deals with the effect of high-power ultrasound waves on the population of two type of pathogenic microorganisms in the washing effluent of tomatoes. The selected bacteria included one type of gram-positive bacteria (Staphylococcus. aureus) and one type of gram-negative bacteria (Escherichia coli) to compare the effect of ultrasound waves on the two different types of bacteria with different cell walls.

In this research, irradiation of high-power ultrasound waves were applied to the water after washing the tomatoes. In this washing effluent, the impacts of ultrasonic power (100, 300, 500 W), radiation time (300, 750, 1200 s), and water temperature (0, 30, 60 °C) were examined on the survival of the S. aureus and Ecoli. The data analysis was done for each experimental runs, using the response surface methodology (RSM), to find the best model for estimating the difference in bacterial population (CFU) before and after irradiation.

The lack of fit was not significant in the analysis of variance and also the value of the explanation coefficient in the model for S. aureus and Ecoli were 0.9721% and 0.9206% respectively. This indicated the appropriate accuracy of the quadratic model in estimating the number of S. aureus and Ecoli remaining in the water after washing tomatoes (for the mentioned independent variables). Gram-negative bacteria (E coli), are composed of an inner thin peptidoglycan cell wall, surrounded by an outer lipopolysaccharide membrane. Gram-positive bacteria (S. aureus), lack an outer membrane but are made up of a multi-layered and very complex structure layers of peptidoglycan many times thicker than is found in the Gram-negatives. In general, the application of ultrasound waves causes to destruction of the mentioned bacteria. The main disinfection effect of ultrasonic waves on the population of S. aureus was power, while for Ecoli the main variable was temperature (based on the highest coefficient of quadratic equations/ 99% confidence level). Through physical, chemical and mechanical effects caused by acoustic cavitation, ultrasound is able to affect the bacterial suspension without producing a side product. The antimicrobial effect of ultrasound is achieved by a combination of chemical effects such as the production of active free radicals and thermal effects such as the production of local hot spots. The observations showed that increasing the temperature first increased and then decreased the effectiveness of ultrasound waves in the inactivation of bactetria. The negative effect of increasing temperature can be related to the decrease in the intensity of bubble explosion.

According to the results of the experimental tests in the average time (750 s), with the simultaneous decrease in temperature (from 60 to 0 ºC) and increase in power (from 100 to 500 W), the destruction effect of ultrasound waves on S. aureus and Ecoli was increased. In the perturbation curves, the simultaneous effect of all three parameters (temperature, time and power), were investigated at the middle points (30 ºC, 750 s and 300 W). At these points, power changes were more effective in reducing S. aureus population, while temperature changes were more effective on the reduction of E coli. The population of S. aureus and E. coli decreased by increasing power of ultrasonic waves. Temperature and power had a synergistic effect, that is, the increase of both parameters led to the decrease of bacteria population. Finally, the tested variables were optimized by desirability in the RSM to minimize the population of microorganisms (S. aureus and E coli simultaneously), and parameters (in the range) obtained for the ultrasonic power, time, and temperature were 300 W, 1200 s, and 0 °C respectively.

Orange is one of the most important citrus species in the economy and industry. This study aimed to dry the oranges with a combined pretreatment of osmotic solution and ultrasound waves to reduce the drying time and improve the quality of the dried product. In this study, a hot air dryer was used to investigate and optimize drying time, water reabsorption capacity of dried samples and shrinkage index of dried samples of orange slices. The samples were pretreated by immersing them in an osmotic solution with brix at three levels of 15, 30 and 45 degrees and applying ultrasonic waves to the samples at three-time levels of 10, 20 and 30 min in the ultrasonic bath. The pretreated samples were dried at three temperature levels of 70, 80 and 90℃ and three hot air velocities of 1, 1.5 and 2 m/s. The results showed that by increasing the concentration of an osmotic solution from 15 to 45 and increasing the ultrasonic time from 10 min to 30 min, the total drying time and the shrinkage index of the product decreased. The water reabsorption of the dried samples was dependent on the variables of ultrasonic time and osmotic solution concentration (P<0.01). The best state of water reabsorption, which was 8.9, occurred at 15° Brix and 30 min of ultrasound. The optimization results showed that the optimal point with the highest desirability index (0.808) occurred at 45° Brix of the osmotic solution, 30 min of ultrasound, 70°C and 1.07 m/s of hot air dryer.

Fish fillet is a corruption-sensitive product that requires several quality and hygiene reviews before consumption. Many methods of fish quality and freshness determined based on destructive and time-consuming tests require manpower and sample sizes. This study evaluated the ability of a non-destructive fusion method of ultrasound, electrical resistance measurement, and colorimetry to monitor the freshness of rainbow trout fillets at refrigerator temperature. For this purpose, the samples of fish fillets were prepared and stored in a refrigerator for 12 days, and physical tests such as ultrasound wave attenuation, electrical resistance, and colorimetry to determine the color component of the fillets in both color space of RGB and Lab, and sensory evaluation (color, taste, odor, and texture) were performed. Also, a chemical test was conducted to determine the fillets ash, protein, and fat during storage. Extracted data from physical tests were subjected to two classification models of neural network and decision tree for determining the best classification method according to the fillet freshness. Various single hidden layer neural networks with zero to ten neurons and decision trees with five algorithms of LMT, REP, J48, RANDOM FOREST, and RANDOM TREE were evaluated. In each model, physical test data were considered as input and storage days as output. Based on the results, the highest classification accuracy (100%) and the lowest mean error value (0.02) were obtained for the neural network with 6 neurons in the hidden layer, and correspondingly 100 percent and nearly zero for the decision tree with J48 algorithm The confusion table of both models also confirmed the classifiers' accuracy. The integrated non-destructive system presented in this study does not require sample preparation. It is accurate, relatively inexpensive, and can be used during the food and fishery process to determine their freshness.

In the present study, two methods were used to extract oil from seeds of Sardasht black grape with normal-hexane as solvent (with and without the use of ultrasonic waves). The results indicated that the optimum conditions to extract the oil when applying hexane as solvent without ultrasound were 30 °C, 60 min extraction time, 15:1 (ml/g) solvent to sample ratio, and mesh of 40 for sample size and 45 °C, 20 min extraction time, 10:1 (ml/g) solvent to sample ratio and sample size at mesh 40 when sonication is applied. The productivity rate in this method (solvent without ultrasound) was 17%. Similarly, the optimum state of extract oil by applying hexane solvent with ultrasonic included (temperature 30 °C, extraction time of 15 minutes, the ratio of solvent to the sample 15/1 (ml/g), the seeds sifted with mesh 40). The productivity rate in this method (solvent with ultrasound) was 25%.

The aims of this study were to assess the energy and economic flows of biodiesel production from olive pomace oil using transesterification method with ultrasound waves. For this purpose biodiesel production from this feedstock were examined through a life-cycle process with considering five main stages of agricultural production, transportation, olive oil extraction, pomace oil extraction and biodiesel production. The results revealed that total energy input were 2601.91 and 3805.04 MJ/ha based on mass-based allocation and economic-based allocation model, respectively. Total energy output (biodiesel as the final outcome) was found to be as 34898.36 MJ/ha. Some energy indicators for production of biodiesel include: energy efficiency, energy productivity, net energy and fossil energy ratio (FER), which were 1.34-0.92 (with no unit), 0.04-0.03 l/MJ, 1413.50-(-) 315.68 MJ/ha, 1(with no unit), respectively for mass-based and economic-based allocation. The share of indirect energy and non-renewable energy were higher than the share of direct energy and renewable energy. Analysis of economic performance indicates that total production value, gross return, net return, benefit to cost (ratio) and productivity were 3.24 million Rial/ha, 1.02 million Rial/ha, 1.01 million Rial/ha, 1.45 (with no unit) and 48.43 l/ million Rial respectively.

In this research, the effect of ultrasound-osmotic dehydration process in different conditions on the drying kinetics parameters of rhubarb was investigated. Before dying process, rhubarb samples were placed in contact of ultrasound-osmotic pretreatment and then dried by convection hot air dryer equipped with circulated fan. The results showed that using osmotic pretreatment at 40% sucrose solution along with 30 min sonication could the drying rate to reach maximum. After optimization and determination the best pretreatment for final drying, drying behavior of rhubarb in optimal conditions by ten empirical models such as Parabolic, Midli-kucuk, Silva et alii, Peleg and suchlike was fitted. The modelling results showed that, Midli-kucuk model due to the highest R2 and the lowest χ2 and RMSE were selected as goodness model to predict drying curve of rhubarb. The values of these parameters were estimated equal to 0.9957, 0.0032 and 0.0256, respectively.

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.