Food Technology
Azade Farazmand; Hossein Jalali; Ali Najafi
Abstract
Introduction Potato strips are one of the most widely consumed products, and due to their high oil content, they have caused public health concerns. Therefore, efforts to reduce oil absorption can alleviate these concerns to some extent. Edible coating is an effective way to reduce oil uptake, because ...
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Introduction Potato strips are one of the most widely consumed products, and due to their high oil content, they have caused public health concerns. Therefore, efforts to reduce oil absorption can alleviate these concerns to some extent. Edible coating is an effective way to reduce oil uptake, because the oil absorption is a surface phenomenon. Edible coatings should adhere well to the surface of the product and provide a uniform and complete coverage for the product. Preventing the migration of oxygen, carbon dioxide, aromas, oils, moisture, improving the appearance of food and mechanical properties. In this study, the possibility of reducing oil absorption in French fries was investigated using okra mucilage and chitosan as edible coatings. Material and Methods The okra was washed and then cut into about 1 cm pieces and poured into containers with lids. Then water in a ratio of 2:1 weight of okra was added to the container and completely covered its surface. The okra were refrigerated for 72 hours until the mucilage was completely extracted. Then the mucilage was smoothed. This solution was considered as 100% mucilage solution. To prepare a 50% solution of okra mucilage, 100% solution was mixed with an equal amount of distilled water and filtered. To produce a solution of 0.75 and 1.5% of chitosan, 7.5 and 15 g of chitosan powder was dissolved in 1000 ml of 1% acetic acid and then adjusted to pH 5. Then 5 g of glycerol was added as a plasticizer. The potato slices were first blanched in 0.5% calcium chloride solution at 90°C for 5 minutes. Then, they were immersed in coating solutions at 60°C for 5 minutes. After coating, the potato strips were fried at 180°C using a fryer and then various characteristics including coating percentage, oil absorption, and moisture content, texture firmness, peroxide value, acid number, color indices and sensory properties were examined. Design Expert 8.0.7.1 software was used to analyze the results and to draw the curves. Results and Discission The results showed that the increasing the amount of chitosan led to better coating formation in comparison with okra. The highest coverage was observed in the concentration of 1.2% chitosan and 0% okra mucilage (2.38%) and the lowest was observed in the control sample (0.11%). It was also observed that with increasing the concentration of chitosan and okra mucilage, the amount of oil absorption decreases. However, the amount of oil absorption in high concentrations of okra mucilage increased slightly. The highest oil uptake in the control sample was 20% and the lowest was observed in the sample of fried strips covered with 41% okra mucilage and 1.5% chitosan at 15.44%. The obtained model of oxidation index was not significant. The effect of okra mucilage and chitosan concentration on the texture of the samples (p <0.05) and the color indices of a* (p<0.01) and L* (p <0.05) were significant. For sensory attributes, the highest and the lowest taste score was observed for samples coated with 100% okra mucilage and 0.75% chitosan and samples coated with 18% okra mucilage and 0% chitosan respectively. Conclusion The aim of this project was to reduce the oil absorption of fried potato strips by coating them with chitosan and okra mucilage. Optimization to minimize the consumption of okra and chitosan mucilage showed that coating with 74% okra and 0.89% chitosan is suitable for coating potato slices. The desirability of this optimization was 71%, which is a reasonable percentage.
Hesam Omrani Fard; Mohammad Hossein Abaspour fard; Mehdi Khojastehpour; Ali Dashti
Abstract
Introduction: One of the new methods for improving the mechanical properties of bioplastics is the production of blending based bioplastics. Recent studies show that proteins, in combination with starch, form a strong network of hydrogen bonds and intermolecular interactions that resulted stable 3-D ...
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Introduction: One of the new methods for improving the mechanical properties of bioplastics is the production of blending based bioplastics. Recent studies show that proteins, in combination with starch, form a strong network of hydrogen bonds and intermolecular interactions that resulted stable 3-D materials. The big problem in the commercialization of blending based bioplastics is the lack of industrial machinery for the continuous production of bioplastics with the direct use of biopolymers. Industrial production of bioplastics is accompanied by increasing heat along with applying the pressure. It is necessary to know the kinetics of thermal degradation of bioplastics to study thermal behavior at different temperatures in order to design bioplastics processing devices and molding machines, software modeling of processes, mass and energy equilibrium, and optimizing energy consumption in the production process along with improving the thermal properties of the bioplastics.
Materials and methods: In this study, the dynamics thermal decomposition of bioplastics prepared from a mixture of potato whole flour-gelatin and glycerol with a control sample consisting of potato whole flour and glycerol was investigated and compared. The gelatin was extracted from chicken feet using chemical methods. In this research, two isoconversional models including Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were considered. Using each of these models, thermal decomposition kinetic parameters were calculated for bioplastic samples.
Result and discussion: The results showed that the maximum activation energy of the mixed bioplastics determined 162 and 150 kJ/mol by FWO method at the conversion ratio of 0.9 and 0.5 respectively, while it was 217 kJ/mol at the ratio of 0.6 for control bioplastics. The amounts of kinetic parameters calculated in this study, were able to determine the thermal behavior at different temperatures and the thermal decomposition process. Also, it can help to redesign and optimize the methods of molding and shaping of potato-gelatin based bioplastics by the use of existing machinery in the industry.
Fatemeh Roshani; Sara Movahhed; Hossein Ahmadi Chenarbon
Abstract
Introduction: Potato is raw food stuff with high popularity worldwide when deep fried. Deep frying is a fast budget process used for preparing savory food. In this process, oil is used both as a heating intermediate and as an ingredient producing calorific products. Nutrition has become a major health ...
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Introduction: Potato is raw food stuff with high popularity worldwide when deep fried. Deep frying is a fast budget process used for preparing savory food. In this process, oil is used both as a heating intermediate and as an ingredient producing calorific products. Nutrition has become a major health concern, particularly in developmental countries where obesity has turned into an ever-increasing problem, mostly among children. Deep frying is a widely-practiced method for cooking fast foods with desirable sensory properties. Frying is a process of simultaneous heat and mass transfer where heat is transferred by a combination of convection and conduction. At high temperatures, a great amount of moisture content is also lost as vapor, compensated by oil uptake in foods. Oil uptake of foods is an important concern associated with their moisture loss. Thus, it is important to examine moisture loss during frying. Today, the interest in production and consumption of low-fat French fries is on the rise. At the same time, the frying method has a great effect on quantitative and qualitative characteristics of foods. The final moisture content in French fries is about 38% of the product’s final weight. sufficient moisture content is therefore required in French fries to achieve both a soft moist core and a crunchy tasty crust. Numerous methods or pretreatments such as ultrasound and drying may improve these properties. Moreover, finding relationships between different variables during deep frying by modelling may provide an optimal control over process conditions thereby improving the quality of the final fried product. In the present study, effects of ultrasound and drying pretreatments on moisture content, oil uptake, activation energy and effective moisture diffusion coefficient in Satina potato slices during deep frying were investigated. Material and methods: 10kg of Satina potatoes were provided and stored at room temperature. Bahar vegetable frying oil containing cotton seed, sunflower and soybean oils was used for frying. For each experiment, potatoes were washed, peeled and sliced by a household French fry cutter with 1.2×1.2×4 cm dimensions. The cut samples were placed in a plate to avoid moisture loss and were washed with distilled water to remove surface starch before frying. The excess surface water was also removed by a hygroscopic paper. Then ultrasonic pretreatments at two frequencies of 20 and 40 kHz were applied for 15min, and the drying pretreatment was also conducted at 60°C for 15min. To fry the samples the fryer was filled with 1.5 lit of oil. The deep fryer was set to adjust temperature and frying time automatically. When the temperature reached the set value, 100-120g potato samples were placed in the frying basket, which was then submerged in oil automatically. The pretreated samples were fried at 170°C and 190°C for 5, 7 and 10 min. Oil uptake and moisture loss during frying were recorded at certain time intervals. Next, the fried samples were removed from the deep fryer and were placed on a mesh tray to remove the excess oil. The oil uptake and moisture content were analyzed. Oil content was measured by the Soxhlet method. It is based on extracting fat from foods using proper solvents. Moisture content was measured by drying in a convection oven at 105°C until reaching a constant weight. Moisture content and oil uptake of potatoes slices during deep frying were also modeled versus time. The factorial experiment was laid out in a completely randomized design with three replications, and means were compared using Duncan’s multiple-range test. SPSS 14 was used for statistical analyses. Results & Discussion: According to the results, samples pretreated with 20 kHz ultrasound at the same temperature and time conditions had higher moisture content than those treated with the 40 kHz frequency. The highest moisture content was found in samples pretreated with 20 kHz at 170°C for 5min. On the other hand, samples receiving 40 kHz ultrasound pretreatment showed higher effective moisture diffusion coefficient and activation energy than those receiving the 20 kHz pretreatment. The highest diffusion coefficient was achieved using 40 kHz at 190°C for 5min, whereas the highest activation energy was observed with 40 kHz at 170°C for 10 min. It should be mentioned that the effective diffusion coefficient was within the 6.95 × 10-8 – 8.80×10-8 m2/s (R2=0.99) range. Activation energy was also in the range of 13.161 – 16.307 kJ/mol (R2=0.99). Conclution: Samples pretreated with 40 kHz ultrasound showed the lowest oil uptake as compared with those pretreated with 20 kHz frequency. The highest oil uptake was observed for samples pretreated with 20 kHz at 170°C for 10 min. Through the multivariable regression analysis, it was found that the exponential model had the best fitting in predicting changes in moisture content and oil absorption.
Vahid Mohammadpour; Mohamad Taghi Hamed Mosavian
Abstract
Frying is an important unit operation used widely both in domestic and industrial cooking. Reduced pressure (vacuum), microwave, deep fat and pan frying are the most important methods of food frying. Final product has good organoleptic quality (colour, texture, and flavour). The accuracy of the knowledge ...
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Frying is an important unit operation used widely both in domestic and industrial cooking. Reduced pressure (vacuum), microwave, deep fat and pan frying are the most important methods of food frying. Final product has good organoleptic quality (colour, texture, and flavour). The accuracy of the knowledge of mass transfer parameters (effective diffusivity coefficient, dimensionless Biot number and mass transfer coefficient) in the case of frying is essential and important for designing, modeling and process optimization. This study is undertaken to develop a more realistic approach for determining mass transfer parameters during frying of potato slices for cylindrical coordinates. These parameters were evaluated from the plots of dimensionless concentration ratios against time in sunflower liquid oil at and . Effective diffusivity coefficient, dimensionless Biot number and mass transfer coefficient ranged between to , to and to , respectively. Effective diffusivity coefficient and mass transfer coefficient were found to increase with an increase in frying temperature, whereas Biot number decreased. An Arrhenius type of relationship was found between the frying temperature and effective diffusivity coefficient.
