Food Technology
Narmela Asefi; Nasibeh Alirezaloo; Pouya Barman Veisi; Haleh Soraiyay Zafar
Abstract
Introduction Sweet Pepper (Capsicum annum) has a very important place among the vegetables produced in the world. Therefore, it is necessary to apply practical solutions to increase their sustainability to develop and improve production. The growing consumer rejection of chemical additives and the ...
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Introduction Sweet Pepper (Capsicum annum) has a very important place among the vegetables produced in the world. Therefore, it is necessary to apply practical solutions to increase their sustainability to develop and improve production. The growing consumer rejection of chemical additives and the demand for more natural products have increased attention to some methods, including the drying method. One of the physical changes that occur during the drying of food is its reduction in volume. Vacuum drying is a method in which water and other solvents that have been absorbed into the volume or surface of the material are removed. Combining vacuum with heating can be an effective way to dry; because in this case, a high level of dryness can be achieved without the need for a large increase in temperature. A thermal process that is applied to vegetables and fruits as a pre-process step for freezing, drying and canning to inactivating enzymes, modifying texture, preserving flavor and nutrients, and extracting Interstitial air. Materials and Methods This study aimed to investigate the impact of various factors ethyloleate (concentrations 0,2,4%), sodium chloride(concentrations 0,2,4%) and blanching on the drying kinetics, physical properties, chemical composition and nutrients of green bell pepper, dried under vacuum at 60°C and pressure of 10 kpa using the response surface methodology. At the end of the drying time, 10 g of the treated samples were weighted to investigate the drying kinetics and the rest of the samples were kept for analysis. To achieve the drying kinetics, the samples were taken out of the oven (Behdad Company, model 3494, made in Iran) at 30 minute intervals and weighed by a digital scale, and dried down to moisture content of 12% ., and then for relevant analyzes on dried samples, the samples were stored in plastic packages until the day of experiments. Investigation of independent and interaction effects of immersion in different concentrations of sodium chloride and ethyloleate solution on the kinetics and drying time separately in blanching and non-blanching samples on the parameters of color, chlorophyll content, phenolic substances and vitamin C remaining in dried Sweet peppers were evaluated using minitab16 software and response level method (RSM). Results and Discussion The results showed that the drying process occur in the range of falling rate and also effect blanching in boiling water for 3 minutes and immersed in an alkaline solution of ethyloleate and sodium chloride with concentrations of 2 and 4% for 1 minute, significantly increase the drying rate. In blanching and treated samples with 4% ethyloleate and sodium chloride, the drying time was about 3.5 hours, while the control sample was dried under the same conditions for 7.5 hours. Pretreatment of samples, showed the chlorophyll content, phenolic compounds and vitamin C were higher than the control sample. Due to the effectiveness of ethyloleate in the protection of ascorbic acid, phenolic compounds and residual chlorophyll, the highest amount of ascorbic acid with a value of 39.77 was related to the samples treated in ethyloleate solution with a concentration of 4% and 4% NaCl and the minimum value of 17.98 was related to the control treatment. The highest amount of residual chlorophyll was 23.6 in the pretreated samples with a concentration of 4% ethyloleate and 4% NaCl and the lowest amount was related to the control sample with a concentration of 12.9%. The color of the dried samples showed that the lowest amount of color changes was related to the non-blanching sample with 4% ethyloleate and 4% NaCl with a value of 4.94. While the blanching and ethyloleate solution had no positive effect on the color of pepper and dried samples were dark. Comparison of blanching with non-blanching shows that blanching samples cause darkening of the primary color of the samples.The best sample in terms of quality and speed of drying, was belonged to the samples which blanched, treated with 4% solution of ethyloleate and sodium chloride. Conclusion In order to achieve the best quality in vacuum drying of pepper samples, pretreatments of blanching and using a concentration of 4% solution of ethyloleate and sodium chloride showed the most desirable quality. The best quality of dried samples were obtained when subjected to constant temperature and pressure during drying conditions. The benefits obtained using the pretreatment of ethyloleate and sodium chloride as an appropriate method of drying include increasing the absorption of water, keeping the chlorophyll, phenolic compounds and vitamin C content with time-saving in drying.
Amir Gitiban; Narmela Asefi
Abstract
Introduction: Dried fruits are one of the most important non-oil exports and the efforts should be made to grow the economy of the country by increasing their exports to world markets. Meanwhile, quince juice contains various minerals including iron, phosphorus, calcium, potassium and rich in vitamins ...
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Introduction: Dried fruits are one of the most important non-oil exports and the efforts should be made to grow the economy of the country by increasing their exports to world markets. Meanwhile, quince juice contains various minerals including iron, phosphorus, calcium, potassium and rich in vitamins such as vitamins A, C and B vitamins. Drying of food is one of the ways to keep its quality and increase its shelflife. During this process, the removal of moisture through the simultaneous transfer of heat and mass occurs. By transferring heat from the environment to the foodstuff, the heat energy evaporates the surface moisture. The drying process has a great impact on the product. In recent years, new and innovative techniques have been considered that increase the drying rate and maintain the quality of the product and infrared drying is one of these novel techniques.. Infrared systems are emitting electromagnetic waves with a wavelength of 700 nm to 1 mm. The advantage of using infrared is to minimize waste and prevent product quality loss due to reduced drying time can be mentioned. The need to predict product quality in each process makes it necesary to model and discover the relationship between factors that can affect the final quality of the product. Artificial neural networks have been considered as a meta-innovative algorithm for modeling and prediction, which can be favored by the ability of these networks to model and predict processes The complexity and discovery of non-random fluctuations in data and the ability to discover the interactions between variables, economical savings in the use and disconnection of classical model abusive constraints (Togrul et al., 2004), the ability to reduce The effect of non-effective variables on the model by setting internal parameters is the ability to predict the desired parameter variations with minimum parameters (Bowers et al., 2000). Materials and methods: In this research, quince fruit (Variety of Isfahan) was purchased as the premium product of Isfahan Gardens and was kept at 0°C in the cold room prior to further experiments. The fruits were removed from the refrigerator one hour before processing and exposed to ambient temperature. After washing, surface moisture was removed by moisture absorbent paper and turned into slices with a constant thickness of 4 mm. The specimens were subjected to pre-treatment with an osmotic solution (vacuum for 70 minutes at a temperature of 40 ° C for 5 hours). For drying the samples, an infrared convective dryer with three voltages (800.400 and 1200 watts) and a constant speed of 0.5 m / s was used. In this way, the samples were placed under infrared lamps on a plate made from a grid and the weight of the samples was measured in a scale of 10 minutes by means of a scale and recorded on the computer. In order to achieve stable conditions in the system, the dryer was switched on 30 minutes before the process. The distance between the samples and the infrared lamp was fixed in all treatments at 16 cm. The drying process continued to reach a moisture content of 0.22 basis. To perform a puncture tests, quince slices were used in a Brookfield-based American LFRA-4500 tissue analysis device. In order to model these parameters in the drying process, the results of examining the quality of the samples, including the firmness of the tissue as well as the drying time, were used as network outputs. The power, concentration and pressure parameters were considered as network inputs. In this research, a multilayer perceptron network (MLP) was used. Due to its simplicity and high precision, this model has a great application in modeling the drying of agricultural products. Many functions in transmitting numbers from the previous layer to the next layer may be used (Tripathy et al., 2008). Result & discussion: The results indicated that the stiffness of the tissue is reduced in vacuum conditions with increased power. So, the least amount of stiffness was related to osmotic sample dried at 1200 watts. By increasing the infrared power, the stiffness of the tissue decreases, the reason for this is probably the volume increase phenomenon that occurs during the rapid evaporation of moisture through infrared rays from inside the tissue. The results showed that at the start of the drying process, due to the high moisture content of the product, the moisture loss rate is high. Gradually, with the advent of time and reduced initial moisture content, the rate of moisture reduction naturally decreases. At lower power, the drying time is longer and with increasing power, the drying time decreases due to the increase of the thermal gradient inside the product and consequently the increase in the rate of evaporation of the moisture content of the product. The results of this study showed that the neural artificial network, as a powerful tool, can estimate the stiffness parameters of the tissue and the drying time with high precision. The most suitable neural network structure to predict these parameters with a 3-7-2 topology along with logarithmic activation functions with a total explanation coefficient above 0.9923 represent the best results. Also, by increasing the drying capacity and using osmotic dehydration, the drying time and the stiffness of the tissue samples is decreased.
Aisan Falaki; Narmela Asefi
Abstract
Introduction: Nutrition research on the health benefits of substances in plant foods (phytochemicals) has recently advanced to a new stage, as ascorbic acid, these phytonutrients is abundant in citrus fruit, and all show physiologic actions that may contribute to cancer prevention. Citrus lemon is an ...
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Introduction: Nutrition research on the health benefits of substances in plant foods (phytochemicals) has recently advanced to a new stage, as ascorbic acid, these phytonutrients is abundant in citrus fruit, and all show physiologic actions that may contribute to cancer prevention. Citrus lemon is an important source of this nutritional qualityand it has low durability due to its high water content (87%). Therefore, some practical solutions such as drying could help to increase their sustainable necessary for improve production. Different drying methods have considerable impact on the quality of final product. Vacuum drying can preserved nutrients and increased the nutritional quality of the final product. This behavior could be related to drying process at low temperatures in the absence of oxygen. In vacuum drying, removal of moisture from food products takes place under low pressure. The lower pressure allow drying temperature to be reduced and higher quality to be obtained than with classical air conventional process at atmospheric pressure. Osmotic dehydration can be used to remove water from heat-sensitive products with low energy consumption at a low temperature. Since osmotic dehydration cannot remove whole moisture but it is good as a preliminary partial dehydration step. Higher osmotic concentration, long time and oxygen resulted in higher loss of antioxidant activity but fit osmotic concentration and time. The osmotic process has received considerable attention as a pre-treatment to reduce energy consumption and improve food quality, besides reducing the drying time in different research studies. The osmotic dehydration as a pre-treatment also inhibits enzymatic growing, retains natural color and retains volatile aromas during the subsequent drying. Sodium metabisulphite is an inorganic compound. It is used as antioxidant (through oxidation prevention) and preservative agent. The purpose of this study was to quantify the flow of soluble micronutrients, such as ascorbic acid, antioxidant agent during osmosis and its effects on the changes of organoleptic characteristics (flavor, taste, color and texture) in final product.
Materials and method: In this study, lemons (shirazi) of uniform quality were purchased from the local market Tabriz city (Iran) and stored at 4ºC then the local temperature reached before use. The prepared slices of lemon with a thickness of 4 mm, were immersed in a solution of sodium metabisulphite (1500ppm) for 10 minutes at room temperature. Then, the influence of three different osmotic solution, (40 % sugar, 15 % salt and 20%:%20 sugar/ salt) on osmotic dehydration (water loss and solid gain) prior to vacuum drying oven (Memmert, Schwabach, Germany) at temperature: 60C and pressure: 70mbar, were investigated the (Shulka and Singh, 2007) method. Moisture content was determined by the oven drying method (AOAC, 1990). The effects of various drying parameters such as osmotic solution and metabisulphite treatment on the quality of dried lemon slices were evaluated. Drying kinetics were presented in terms of the temperature of the product during drying, drying curve and drying time and quality aspects were studied in terms EC50 by the 2, 2-diphenyl-1-picrylhydrazyl absorption rate in spectrophotometer method (Cemeroglu, 2010), ascorbic acid by the 2, 6-dichlorophenol Indophenol titration method (Cemeroglu, 2010), shrinkage by the fluid movement (by ethanol) method (yasaemehrjerdi et al, 2012), and sensory evaluation by the ratings table method. Also the experiment was conducted according to a completely randomized design in triplicates. Data were evaluated by analysis of variance (ANOVA), using Design Expert software, and version dx7-trial.
Result & discussion: The result showed that the pretreatment with osmotic solution, has significant effect (level 1%) on physicochemical and organoleptic characteristics. In this study, shrinkage levels were reduced to an average of 20 percent because of the evolution of volume of dried lemon tissue throughout osmotic dehydration in osmotic aqueous solution were closely supported by microstructural and ultrastructural changes. The observed behavior of structural parameters could be partially explained in terms of the multicomponent diffusion process occurring during osmosis as well as the relaxation of structural stresses of the compressed viscoelastic cell walls. Water loss in samples immersed in sodium metabisulphite was increased, while EC50 (reduced EC50 amount that’s mean increased antioxidant capacity) and that ascorbic acid content were decreased. Also combined osmotic solution (salt 20%- sugar 20%), considerable in water loss and solid gain due to the combined osmotic solution were increased. Mass transfer in samples was increased by increasing the osmotic pressure using salt. The sugar solution can be preserved fruit nutrients and increased the sensory quality of the final product through preserved antioxidant capacity and ascorbic acid content. model presented the best fit for the observed data and sample immersion in sodium metabisulphite with sucrose osmotic solution selected. Since, changing the original taste of fruit in osmotic dehydration considered to be a negative factor. Therefore, the selection of the best solution must be based on the sensory properties. Based on the obtained results, the best osmotic solution for dried lemon was found to be the sugar solution.
