Food Engineering
Hassan Sabbaghi
Abstract
Introduction: Doughnuts are fried foods that absorb significant amounts of oil, and commercial doughnuts made from wheat flour typically contain 24 to 26 percent oil. The use of additives, especially hydrocolloid compounds, in reducing the oil uptake in doughnuts is a practical method because there is ...
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Introduction: Doughnuts are fried foods that absorb significant amounts of oil, and commercial doughnuts made from wheat flour typically contain 24 to 26 percent oil. The use of additives, especially hydrocolloid compounds, in reducing the oil uptake in doughnuts is a practical method because there is no need to make changes in the industrial design of the equipment. Usually, the level of these compounds used to achieve the desired properties in food systems is less than 2% dry basis. When these compounds are added to the dough, they form a gel as soon as possible, which has a high water holding capacity in contact with hot oil, and this will be effective in maintaining and controlling the moisture content of the product and preventing oil penetration. Controlling moisture outflow from the product reduces the rate of moisture migration and compounds from the food into the frying oil, and subsequent peroxidation reactions in the oil consumed are reduced, thus increasing the useful life of the oil. Therefore, in this study, the effect of xanthan gum and carboxymethylcellulose on doughnut quality characteristics was studied. Materials and Methods: For this purpose, in the formulation of doughnut dough, xanthan gums, carboxymethylcellulose and a combination of these two gums (50:50) were used at the rate of 0.5, 1 and 1.5 percent based on the weight of the dry matter of the dough. The doughnut dough was prepared and molded. The fermentation was carried out for 30 minutes under similar industrial conditions (40°C and 40% humidity). Then the frying process at 180°C, icing and packaging were performed, respectively. The moisture content of the dough and doughnuts, the oil uptake of doughnut, density, color and the porosity ratio of the samples were measured. Also, the qualitative characteristics of shelf life, including soft tissue assessment, non-absorption of icing and non-growth of mold were investigated within 14 days. Statistical analysis was performed in a completely randomized design (p<0.05). Results and Discussion: The results showed that, the moisture content of the samples always increased with elevating the percentage of hydrocolloid compounds. Oil absorption decreased with increasing gum percentage and the lowest oil content was observed in the samples containing xanthan gum. Unlike xanthan, the density decreased and the volume increased with elevating the percentage of carboxymethylcellulose gum. Therefore, the highest porosity and softness of the tissue were found in samples containing carboxymethylcellulose. The brightness parameter (L*) was higher in samples containing xanthan, which could be due to the higher moisture content. The red parameter (a*) was also higher in the samples containing xanthan, which due to the higher compression of the product, a relatively more red pigment was observed with increasing xanthan level. The yellowness parameter (b*) in xanthan-containing samples was lower due to reduced oil absorption. The intensity of the color changes (dE) decreased as the percentage of gums increased. Non-absorption of icing was less in hard sample containing xanthan, which could be due to xanthan's competition with gluten in suction of surface water. Mold growth was not observed for any treatment. Overall, the best additive ratio of xanthan gum was 0.5% in terms of reduced oil absorption. Also, the use of carboxymethylcellulose at the level of 0.5% alone could improve the softening of the product texture and made the doughnut with larger volume. Simultaneous use of xanthan gum and carboxymethylcellulose showed behavior under effect of xanthan gum.In general, xanthan gum was more effective than carboxymethylcellulose gum in reducing oil uptake and moisture retention at test levels. Xanthan has shown the greatest reduction in oil absorption due to its thermal gelling and thickening properties, as it has a high capacity for water retention when product is in contact with hot oil. Since the xanthan gum is inexpensive, its effects on product volume can be further investigated in research work, along with bulking agents or other hydrocolloid compounds.
Food Engineering
Fatemeh Heydari; Mohebbat Mohebbi; Mohammad Javad Varidi; Mehdi Varidi
Abstract
The effect of various levels (5, 10 and 15%) of fish protein concentrate (FPC) in batter formulation was investigated. The physicochemical properties of chicken nugget were evaluated in order to find the optimium level of FPC in batter formulation. Flow behavior showed that the control batter and a treatment ...
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The effect of various levels (5, 10 and 15%) of fish protein concentrate (FPC) in batter formulation was investigated. The physicochemical properties of chicken nugget were evaluated in order to find the optimium level of FPC in batter formulation. Flow behavior showed that the control batter and a treatment contains of 7.5% FPC had higher viscosity. Moisture loss and fat uptake in control sample was higher than all treatments contain FPC in both deep fat and air fryer. Thicker crust resulted by higher level of FPC in batter leads less oil uptake during frying. Moreover, the samples contain FPC had the highest score in terms of texture and overall acceptability. In spite the fact that nuggets contain FPC had the high rate of our research priorities, however, the level around 15% considered as a limitation. Using desirability optimization, the range between 7.5- 8% of PFC in batter formulation was selected as the best level.
Safie Khalilian; Aman Mohammad Ziaiifar; Ali Asghari; Mahdi Kashani-Nejad; Mohebbat Mohebbi
Abstract
Introduction: Thermal properties of food during the frying process and mass transfer mechanisms (water and oil) can help in controlling the quality of the fried product (Fiszman et al., 2005). During the frying process, heat was transferred from the oil to the sample surface that it increases the temperature ...
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Introduction: Thermal properties of food during the frying process and mass transfer mechanisms (water and oil) can help in controlling the quality of the fried product (Fiszman et al., 2005). During the frying process, heat was transferred from the oil to the sample surface that it increases the temperature almost to 100 °C, the water evaporates and moved out. The sample surface was covered by bubble layers with various size and distribution. The formation of vapor bubbles on the samples surface have been effective on the micro-flows which is one of the important factor in the coefficient of heat transfer (Sahin et al., 1999). Therefore, knowledge of the relationship between the boundary layer and the surface heat transfer coefficient can determine the thermal behavior and kinetics of the migration of moisture and oil. Eggplant (Solanum Melongena L.) is one of the major agricultural crops of Asian and Mediterranean countries. Iran after China and India has achieved third place in eggplant production, which has made it remarkable, and economical. Eggplant absorbs high amounts of oil during the frying process due to its high moisture content (more than 90%) and high porous structure even if the residual water content is still quite high after frying.
Materials and methods: Fresh eggplants (Solanum melongena L. family Solanaceae) were obtained from the local market and stored at 4°C. Eggplant samples were washed with water tap and cut with manual mold into equal and similar cylindrical pieces (2.5×1cm). They were then washed with distilled water and surface water was removed using tissue paper. Finally, the samples were packed by poly-ethylene in order to prevent surface drying. A commercial sunflower oil was purchased from Ladan Factory, Iran.
Eggplant samples were dried at different temperature of hot air drying 40, 70, 100 and 130°C until moisture content 5 and 12 db%. Samples were drawn from the drier after drying, cooled at room temperature (25°C) and deep fat fried.
A domestic deep fat fryer with temperature control of ± 1°C (Seb, France) was used for carrying out frying operations. The fryer was filled with 2.5 l sunflower oil. The eggplant to oil ratio was kept at 1:50 w/v to reduce temperature variation in the oil bath. The frying was performed at 130, 150 and 170 °C for regular interval times 1, 2, 3, 4, 5 and 6 min. The frying oil was changed after 10 h of frying time. The samples were immediately removed from oil and were located on wired plate for draining and remove excess oil on the surface, and allowed to cool at room temperature before analyses. All experiments were performed in triplicates and the presented results are the mean of the obtained values.
Oil and moisture content were determined according to AOAC, 1995.
K type thermocouples (copper-nickel) with accuracy of ±1°C were used to measure the temperatures of samples. Temperature acquisition TC-08, Pico® (Technology Limited, England) with accuracy ±0.5°C and temperature controller PID Rex- D-100® (RKC) were used to data collection and oil temperature control, respectively.
In this study, convective heat transfer coefficient was calculated between surface sample and oil according to Farinu and Baik (2008).
In order to predict surface heat transfer coefficients and mass transfer kinetic eggplant samples during deep frying was used artificial neural networks. Then, the 4 inputs including: frying temperature (130, 150 and 170 °C), frying time (1, 2, 3, 4, 5 and 6 min), 4 pre-treatments drying temperature by hot air (40, 70, 100 and 130 °C) until the two moisture levels (5 and 12 %db) were used and output parameters including moisture and oil content, heat transfer coefficient with two replications which in total of 288 data were used to form the network structure.
Results and discussion: Results of this study showed that there is some complicated relationship between convective heat transfer and moisture and oil content. In addition, the convective heat transfer coefficient in up and down surface of the sample showed that oil absorption will be from upper surface. This phenomenon can be attributed to upper surface due to more bubbles of vapor out of the sample. This leads would slower the formation of crust on the upper sample. Finally, channels and cavities of the upper level will be more susceptible to the contact of oil. The results of predictive parameters of heat and mass transfer during deep frying eggplant samples using artificial neural network multilayer perceptron as a non-linear method showed closely relationship with experimental data. It indicates that the proper functioning of this method for modeling and studying the relationship between heat and mass transfer phenomena during deep frying of eggplant samples.
Hassan Sabbaghi; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad
Abstract
Introduction: Frying phenomena occur during the immersion of the product in oil at a temperature of 150–200 ºC, where a simultaneous heat and mass transfer take place. This is the most popular thermal processes of potato cooking. This fast drying is critical to improve the mechanical and structural ...
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Introduction: Frying phenomena occur during the immersion of the product in oil at a temperature of 150–200 ºC, where a simultaneous heat and mass transfer take place. This is the most popular thermal processes of potato cooking. This fast drying is critical to improve the mechanical and structural properties of the final product. These conditions lead to high heat transfer rates, rapid cooking, browning, texture and flavor development. The fried potato is easier to transport and provides better texture. Researchers have assumed the existence of two regions for fried product, separated by an interface: the core (unfried) and crust (fried) regions. In general, frying process is very complex for two main reasons: i) due to the simultaneous heat and mass transfer between food material and frying oil, ii) due to the progressive deterioration of the oil and structural changes in foods (crust and core regions). The moving boundary problem may be found in many areas of frying research involving heat and/or mass transfer. In this study, heat and mass transfer is entirely investigated during frying of potato strips. The transport phenomena during frying are including: i) Heat convection from the hot oil to the interface via the crust region, ii) Water evaporation at the moving interface at a temperature of 100 ºC, iii) The unsteady state heat conduction in both regions of crust and core, iv) The oil uptake into food. As a result, high temperature and low moisture conditions develop as frying proceeds. Water vapor bubbles escaping from the surface of the food cause considerable turbulence in the oil. Therefore, Heat and mass transfer are dependent on each other during frying process. In fact, heat and mass transfer during frying can be controlled by heat transfer at the product surface. Evaporation rate depends on the temperature difference between oil and boiling point of water. There is little information on modeling, both empirical and phenomenological, for moisture loss and oil uptake during frying. Knowledge of accurate heat and mass transfer parameters is important for modeling processes. Designing of frying processes is possible through the use of mathematical models. The aim of this study is to develop a more completely and realistic approach for determining of heat and mass transfer parameters and their relation to oil temperatures. The main process parameters influencing oil uptake are frying temperature and duration. Heat transfer coefficients for different oil temperatures determined using simple method. Mass transfer of water was assumed to be governed by Fick's law of diffusion. For more details, empirical models were used to describe the mass transport in forms of moisture and oil.
Materials and Methods: The frying operation of potato strips was performed in the fryer that was equipped by thermo controller system with K type thermocouple at three different oil temperature of 145, 160 and 175 ºC for 60, 120, 180 and 240 seconds. The core temperature changes of product recorded on computer during process using T type thermocouple connected to data logger. The moisture and oil content of samples measured for each process time and temperatures. The heat and mass transfer parameters such as kinetic coefficients of moisture (Km) and oil transfer (Ko), mass transfer coefficient (Kc), effective diffusivity (D) and heat transfer coefficient (h) were evaluated with dimensionless temperature and concentration ratio plots and also empirical equations. Relationship of these parameters to the temperature of the oil investigated using the Arrhenius equation. Thermal conductivity of potato strips during frying determined as a function of moisture content using the Anderson and Spell equations.
Results & Discussion: The results showed that mass transfer Biot number (Bim), mass transfer coefficient (Kc) and effective moisture diffusivity (D) increased significantly with increasing in oil temperature. In regression models, the linear correlation between kinetic constant of water loss and oil uptake was observed that is verification on effect of drying pretreatment on reducing oil uptake. In fact, with increasing of oil temperature the kinetic constant of water loss increased and caused increased in kinetic constant of oil uptake. Kinetic models could correctly confirm determination of mass transfer parameters. The heat transfer Biot number (Bih), convective heat transfer coefficient (h) and product thermal conductivity (k) decreased significantly with an increase in process temperature. With increasing in the rate of evaporation, following greater amount of input energy used for water loss. This would reduce the amount of available energy to increase internal energy of product and thus reduce the convective heat transfer coefficient at high temperatures. Frying process caused remove of water from product and increasing of porosity, thus observed gradually fell in thermal conductivity. Although the minimum thermal conductivity at various temperatures are close together, but two equations of Anderson and Spell showed significant difference for values of thermal conductivity and Spell was more close to published papers. High activation energy is achieved for lower moisture content that is normally due to the strong water-substrate interaction.
Hassan Sabbaghi; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad
Abstract
Introduction: Texture is one of the most important attribute in foods and is always issues for the manufacturing of fried products, because texture plays a crucial role in consumer acceptance and the perceived quality of foods. Prediction of changes in texture during frying can be helpful in process ...
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Introduction: Texture is one of the most important attribute in foods and is always issues for the manufacturing of fried products, because texture plays a crucial role in consumer acceptance and the perceived quality of foods. Prediction of changes in texture during frying can be helpful in process control. Structurally, this quality parameter in fried potato strip made from the formation of a composite structure with two layers as: dry and oily outer layer (crust), and a moist or soft interior layer (core). So, the explanation of texture development during frying is difficult because of the innate heterogeneity of the fried potato tissue. Moreover, both thermal degradation and texture development are functions of variables such as processing time, oil temperature and vaporized moisture of product. Textural changes during frying described as the result of various physical, chemical, and structural changes involved in the frying process. One solution to reduce the complexity of real bio systems in engineering is using various empirical correlations. Application of these relations for prediction of textural changes during frying can help us for understand the proper conditions to achieve desired texture. The purpose of the present investigation was to study the influence of the frying temperatures on texture of potato strips. In fact, textural changes during various stages of frying potatoes including initial heating, surface boiling and falling rate period were investigated. Texture evaluation is done by mechanical measurements, because the stimulus in texture perception is mainly mechanical. Also, textural studies are not clearly performed up to now with focus on cook value as a main factor in potato frying. According to the definition of cook value, this parameter indicates total time of baking in 100 °C. Fractional conversion applied as a technique for analyzing texture degradation kinetics and softening of vegetables upon prolonged heating. A few assumptions were made during study: i) Potato shrinkage is neglected ii) Product is not completely dried iii) The stages of frying were considered separable only based on surface and center temperature iv) Texture of potato strips affected by cook values of each frying stages. Materials and methods: The potato strips with specified size fried at a constant temperature of 145, 160 and 175 °C for 30, 60, 90, 120, 150, 180, 210 and 240 seconds. Then, various stages of the process were separated using surface and center temperature profiles of product that were recorded by data logger and T-type thermocouple in computer. Heating extremity of each stage was determined using cook value parameter. Mechanical properties such as apparent modulus of elasticity (Secant modulus) and toughness were used to show which occurred during frying. The secant modulus (S) variations described using fractional conversion model. The degree of cooking for each sample was expressed in term of cook value and its relationship with the overall acceptance of product was examined. Finally, the suitable temperature was determined by sensory evaluation to achieve the desired texture to determine the proper cook value and to prevent over cooking of product. Results and Discussion: The stages of frying by immersion for experimental conditions can be divided as: I. Initial heating (The first 30 seconds for all oil temperature) II. Surface boiling (30-60 s). III. Falling rate (up to end, longest period). IV. Bubble end point (not considered). Generally, higher oil temperature showed larger center and surface cook values because of the fast temperature increase inside product. During initial heating period (I) because of temperature increase without boiling, the changes in cook values versus time are negligible. Surface cook value increased slowly compared with core during surface boiling. Maximum cook value for core temperature was higher, because of the vapor pressure at the center of the product and thus water evaporation at temperatures above 100 °C (cook value above 1 second). During falling rate period due to gradual reduction of evaporation rates, and thus the vapor pressure drop within product, boiling temperature reduced to 100 ° C. The major part of texture destruction occurred during initial heating period and the changes of textural characteristic were going to be constant at the end of surface boiling. The slope of the regression line for fractional conversion model decreased as temperature increased and therefore product was harder, but equivalent value of secant modulus was independent of process temperature. The consumer texture desired was found for temperature of 160 °C with medium cook value. The kinetics of potato softening followed an exponential decay equation with good correlation on empirical data. The temperature dependence of the degradation rate was reliably modeled by the Arrhenius equation. Activation energy (Ea) for model parameters Se and Ks was 13047.12 and -24949.74 J/mol, respectively. Negative Ea for kinetic constant (Ks) indicated an inverse relationship with oil temperature. In addition, elevated oil temperatures caused less softening of French fries because of higher cook value and thus higher evaporation rate.
Milad Fathi; Seyed Mohammad Ali Razavi
Abstract
In this study, potential application of image texture analysis as a non-destructive method for automation and prediction of mechanical properties of carrot chips was investigated. Samples were fried at different processing conditions and moisture content, colour parameters (i.e. L*, a*, b* and E) ...
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In this study, potential application of image texture analysis as a non-destructive method for automation and prediction of mechanical properties of carrot chips was investigated. Samples were fried at different processing conditions and moisture content, colour parameters (i.e. L*, a*, b* and E) and mechanical properties (i.e. hardness and apparent modulus) were determined. Hardness and apparent modulus increased by increasing frying temperature and time. Four image texture features namely contrast, correlation, energy and homogeneity were calculated using gray level co-occurrence matrix. The results showed contrast and energy of gray level images were well correlated with hardness of fried samples in compression and puncture tests. Correlation coefficients of 0.97 and 0.98 between four image texture features and hardness were obtained in compression and puncture tests, respectively. Results indicate that image texture analysis can be successfully applied as a non-destructive method for estimation of mechanical properties of carrot.
Hassan Sabbaghi; Aman Mohammad Ziaiifar; Alireza Sadeghi Mahoonak; Mahdi Kashani-Nejad; Habibollah Mirzaee
Abstract
Introduction: Heat transfer processes are important for almost all aspects of food preparation and play a key role in determining food safety. Temperature difference between the source of heat and the receiver of heat is the driving force in heat transfer. Convection is the transfer of heat by the movement ...
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Introduction: Heat transfer processes are important for almost all aspects of food preparation and play a key role in determining food safety. Temperature difference between the source of heat and the receiver of heat is the driving force in heat transfer. Convection is the transfer of heat by the movement of groups of molecules in a fluid. The groups of molecules may be moved by either density changes or forced motion of the fluid. In a typical convective heat transfer a hot surface heats the surrounding fluid, which is then carried away by fluid movement. The convection heat transfer coefficient or h value is defined as the rate of heat that will be convected at the product surface–fluid interaction through a unit surface area of the material if a unit temperature gradient exists between the product surface and the surrounding fluid and is very important in modeling and design of frying systems for foods. Frying is a very turbulent process with random and dynamic movement of small bubble particles over the boundary layer of the product surface. Deep fat frying is a very fast method of food processing among conventional heat transfer methods. The frying by immersion can be divided into four stages: (1) initial heating (the temperature of the internal part is slowly increased to boiling point); (2) surfaces boiling (crust formation and higher oil turbulence); (3) falling rate (long period, vapor transfer at the surface decreases) and (4) bubble end point (dried product). These four states during frying can be generalized as non-boiling phases (stages 1 and 4) and boiling phases (stages 2 and 3). So, Convection heat transfer during immersion frying may be divided into two stages: 1) free convection during initial heating of the material and 2) forced convection during the boiling phase. In this study, the convective heat transfer coefficient investigated as a function of the water loss rate during frying process due to the effects of evaporation and boiling on this thermal parameter. Understanding of changes in heat transfer coefficient for thermal control of the frying process is very important to achieve optimum quality of product. Materials and Methods: The potato stripes with specified size are fried at temperature of 145, 160 and 175 °C for 60, 120, 180 and 240 seconds using sunflower oil. The center and surface temperatures of potato stripes were recorded with two-second intervals using T type thermocouple and data logger. Moisture content of French fries was measured by drying them within an oven instrument. Mean moisture and oil content of potato stripes was measured. The h value was estimated and its changes studied during process using heat energy balance between the sample and oil by assuming that total heat transferred by convection from oil to potato is equal to the sum of energy spent on heating potato and energy spent on water evaporation. Moreover, changes in the fraction of total heat used for evaporation at different temperatures were expressed as an empirical model. Results and Discussion: The results showed that the temperature at the center increased up to the evaporation temperature (“A” zone: about 60 seconds after process beginning). Then, it remained constant at this temperature for a while due to evaporation (“B” zone: about from 60 s till 160 s). This constant temperature period decreased as temperature increased. After this period, the center temperature approached to that of oil (“C” zone: increasing product surface temperature to oil temperature). These various stages of the process were separated. The moisture loss rate was high at the beginning of frying and oil uptake increased as the moisture content diminished. As oil temperature increases, the sample moisture content for the same frying period decreases since an increase in temperature results in a higher kinetic energy for water molecules leading to a more rapid moisture loss in form of vapor. The heat transfer coefficient is increased as the oil temperature increased and at the first time of process observed higher h value. It was due to more water loss rate and so the higher turbulence within the oil before crust formation and for elevated temperatures. The maximum heat transfer coefficient for the temperatures of 175, 160 and 145 °C is estimated 943.68, 847.81 and 682.64 W/m2°C, respectively. Estimated h value also shows a linear increase with water loss rate. Since most of the energy used is associated with the evaporation of water present in the potato, for lower temperatures, the fraction of total heat needed to complete the evaporation is higher and it also represents lower h values by reducing the oil temperature. Also, the variation in the fraction of total heat used for water evaporation showed exponential rise to maximum behavior. Conclusion: The proposed model for studying evaporation heat fraction fitted experimental data properly, with standard error values range of 0.01-0.03. Evaporation heat fraction could have been affected by oil temperature changes, water loss rate and h value (linear depend with the water loss rate) during process.
Mahdi Barmour; Jalal Dehghan nia; Babak Ghanbarzadeh
Abstract
The objective of this study was to evaluate the effect of process conditions and different pretreatments including ultrasound, microwave and osmotic dehydration on mass transfer and oil uptake during deep fat frying of potato slices. Ultrasound pretreatment was performed at frequency of 40 KHz for 10 ...
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The objective of this study was to evaluate the effect of process conditions and different pretreatments including ultrasound, microwave and osmotic dehydration on mass transfer and oil uptake during deep fat frying of potato slices. Ultrasound pretreatment was performed at frequency of 40 KHz for 10 and 30 minutes, microwave pretreatment was conducted at 5 W/g power and osmotic dehydration pretreatment was done in NaCl solutions with concentrations of 1 and 3 percent. Potato slices were then fried at 150, 170 and 190°C for 90, 180, 270 and 360 seconds. The results showed that ultrasound pretreatment for 10 minutes increases oil uptake of samples as compared with control sample, but when samples were exposed to ultrasound for 30 minutes, oil uptake was decreased. In addition, microwave pretreatment reduced oil uptake of potato slices insignificantly. Furthermore, osmotic dehydration pretreatment reduced oil uptake. In order to model oil uptake, experimental data were fitted with 6 models. The aforementioned models had the highest R2 and a minimum value of RMSE.
Behdad Shokrollahi Yanchedhmeh; Mohebbat Mohebbi; Mehdi Varidi; Elham Ansarifar
Abstract
In recent decades, as the result of industrial life, consuming fried and fast foods have increased significantly. Excessive use of fat, especially saturated fats and trans fatty acids is one of the important factors that increases heart diseases, weight gain, and cancers. Therefore, using effective methods ...
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In recent decades, as the result of industrial life, consuming fried and fast foods have increased significantly. Excessive use of fat, especially saturated fats and trans fatty acids is one of the important factors that increases heart diseases, weight gain, and cancers. Therefore, using effective methods for decreasing fat absorption not only retains desirable features but also seems essential. In this study, the effect of subtituting wheat flour with lentil flour on the batter formulation (in different level of 10, 25 and 50 percent) on the rheological properties of batter, amount of moisture and oil content, and color of fried crusts investigateded by using a deep-fried crust model at three temperature (140, 160 and 180oc) and for 90, 180, 270 and 360 s frying times. Consistency index showed a significant increase by increasing subtitution of lentil flour in batter formulation. Moreover, all the batters showed shear-thinning behaviour. The findings indicated that Batter formulations, temperature and frying time significantly (p < 0.05) affected moisture content, oil content and color of fried Crusts. Results of the study indicated that as frying time increased, the amount of moisture content reduced and increased the oil content of the final product. Also, with increasing substitution of lentil flour, moisture removal decreased and therefore, oil uptake decreased. 50% lentil flour substituted samples was found to be an effective formulation in decreasing oil content of fried crusts at all the times . Conrol sampel showed the lowest moisture content and highest oil content among all the formulations. 50% lentil flour substituted samples was found to be an effective formulation in decreasing oil content of fried crusts at all the times . Conrol sampel showed the lowest moisture content and highest oil content among all the formulations. Temperature leaded to an increase in moisture removal and an increase in oil content. By increasing frying time, temperature and subtitution of lentil flour in battre formulation, L*parameter decreased and a* and b* increased.
Masoud Hashemi Shahraki; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad; Mohammad Ghorbani
Abstract
Oil uptake occurs mainly during cooling immediately after frying. Post-frying centrifuge step used to remove the attached oil to the surface of friedproduct. Response surface methodology (RSM) technique was used to develop models for the responses to the centrifugal force (100, 200 and 300 rpm) and centrifugal ...
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Oil uptake occurs mainly during cooling immediately after frying. Post-frying centrifuge step used to remove the attached oil to the surface of friedproduct. Response surface methodology (RSM) technique was used to develop models for the responses to the centrifugal force (100, 200 and 300 rpm) and centrifugal time (20, 50 and 80 s), frying temperature (140, 170 and 200 C) and frying time (4, 6 and 8 min), Investigated factorsoptimized with respect totheoil and moisture contents, color and textural parameters. The models showed very well fitness with experimental data. The coefficients of obtained models with RSM, was optimized by using genetical gorithms and was observedthat GA optimized models showingbetterfitnesswith theexperimentalresults than RSM models. The resultssuggest thatpost-frying centrifuge step in300 rpm for 80 sand fryingin 175-180Cfor 7-8 minleadsto French fries withlowestmoisture and oil contentand best color and texture.
Arash Ghaitaranpour; Masoud Taghizadeh; Hamed Mahdavian Mehr; Mohammad Reza Abdollahi Moghaddam
Abstract
Bezhi (or Beji) is a special sweet and fried cookie which is produced traditionally in west region of Iran. In this study, the effect of different temperature levels (150, 165 and 180°C) and frying time (1 to 8 min) on physicochemical properties of Bezhi was investigated. The obtained results showed ...
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Bezhi (or Beji) is a special sweet and fried cookie which is produced traditionally in west region of Iran. In this study, the effect of different temperature levels (150, 165 and 180°C) and frying time (1 to 8 min) on physicochemical properties of Bezhi was investigated. The obtained results showed that increasing frying time up to the first 3 minutes causes a significant increase in sample volume. Although, further increase in frying time was not accompanied by volume increase but the mean volume was decreased significantly. Generally any increase in the studied parameters (temperature and frying time) would increase the samples’ diameter while other dimensional characteristics remained unchanged. Moreover, increasing temperature and frying time would increase the samples’ hardness as well as their color changes (∆E). L* value showed decrease when increasing studied parameters. The rate of decrease in L* in the studied temperature levels (150, 165 and 180 °C) were found to be 0.00987, 0.07665 and 0.11250 S-1 respectively. In addition a* value was increased by increasing the studied parameters while b* remained unchanged. The activation energy for the enzymatic reactions in Bezhi samples was 31.12 Kcal/mole which demonstrates the high effect of temperature on these reactions in the studied temperature range. Temperature and frying time showed considerable effect on the crust formation of samples. While the maximum crust thickness at 150 °C was reached to 0.55 mm, the value of 1.45 mm was recorded as the maximum crust thickness at 165 and 180 °C. So oil temperature and frying time have an important effect on physiochemical properties of Bezhi.
Reza Farhoosh; Hashem Pourazerang; Mohammad Hossein Hadad Khodaparast
Abstract
Measuring the rate of changes in total polar compounds (TPC) content and polar fractions, the oxidative stability of canola oil during frying process as affected by bene kernel oil (BKO, 0.05 and 0.1%) and tert-butylhydroquinone (TBHQ, 100ppm) was investigated. It was observed that the TPC content increased ...
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Measuring the rate of changes in total polar compounds (TPC) content and polar fractions, the oxidative stability of canola oil during frying process as affected by bene kernel oil (BKO, 0.05 and 0.1%) and tert-butylhydroquinone (TBHQ, 100ppm) was investigated. It was observed that the TPC content increased linearly with frying time (R2 > 0.98). The canola oil containing the BKO (especially 0.1%) was significantly capable of increasing oxidative stability. The TPC analysis by high-performance size-exclusion chromatography allowed the separation and quantification of triglyceride polymers (TGP), triglyceride dimers (TGD), oxidised triglyceride monomers (oxTGM), diglycerides (DG), and free fatty acids (FFA) during frying. The ability of the BKO to resist the TGP and oxTGM formations was near to that of the TBHQ, whereas the ability of the BKO to resist the DG and FFA formations was better than that of the TBHQ.
Fereshteh Dehghan Nassiri; Mohebbat Mohebbi; Farideh Tabatabaei Yazdi; Mohammad Hossein Hadad Khodaparast
Abstract
The objective of this work was to determine the effect of pre-frying elimination through the addition of methylcellulose and the influence of wheat flour partial replacement with corn flour (5 and 10%) on some quality factors of deep fat fried shrimp nuggets and compare the results with traditional process ...
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The objective of this work was to determine the effect of pre-frying elimination through the addition of methylcellulose and the influence of wheat flour partial replacement with corn flour (5 and 10%) on some quality factors of deep fat fried shrimp nuggets and compare the results with traditional process including pre-frying step. All batters showed shear-thinning behavior (n ≤ 0.624) and provided a good fit with power law model (R2 ≥ 0.979). Methylcellulose produced a significant increase in the consistency index of the batters. The highest pick-up value (57.68%) and the lowest oil content were found in 2% MC added batters that contained 5% corn flour, which was consistent with its high apparent viscosity. Results showed that the pre-frying elimination is an effective way in reducing oil content (%46) in deep fat fried shrimp nuggets.
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.
