Hamed Mahdavian Mehr; Arash Koocheki; Mohebbat Mohebbi
Abstract
Introduction:Deep fat frying is a cooking method where oil is used as the heat transfer medium, in direct contact with food at a temperature above boiling point of water. The aim of this process is to combine short cooking times with unique characteristics. It also involves heat and mass transfer simultaneously. ...
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Introduction:Deep fat frying is a cooking method where oil is used as the heat transfer medium, in direct contact with food at a temperature above boiling point of water. The aim of this process is to combine short cooking times with unique characteristics. It also involves heat and mass transfer simultaneously. During frying time, the mass transfer is characterized by the dynamics moisture loss from the food and the fat uptake into the food. There is some experimental evidence showing that water loss and oil absorption are correlated and progress with specific kinetic. In the meantime, oil uptake of product is an important issue, affecting the nutritional and organoleptic qualities of fried foods. However, one problem associated with fried foods is the considerable amount of oil absorbed during the deep frying process. It is affected by oil temperature, frying time, initial water content of food ingredients, product surface area, the ratios of product weight to frying oil volume, pretreatments and many other factors. So far, several approaches have been suggested for decreasing oil uptake during deep frying of fried foods. One way to decrease oil absorption in foods is referred to batter coating. In this regard, the ingredients and flow behavior's properties of batter are the most important parameters to determine the performance of batter coating and reduction of oil uptake in the final product. In the batter formulations, proteins and gums can be used as important and effective components, because they have great water bonding and barrier properties, which has strong impact on reduction of oil uptake during frying. Therefore, the objective of the present study was to assess the effects of replacement of Godume shahri seed gum (0.5 and 1%) or soy protein isolates (2 and 4 %), as part of the wheat flour in batter formulation, on rheology of batter, batter pickup and mass transfer kinetic parameters during deep frying of chicken nuggets.Materials and method:Raw materials including fresh chicken breasts, onion, salt, hot pepper, wheat flour, baking powder, and 100% pure sunflower oil were purchased from local markets. SPI (92% protein. w/w, db) were obtained from FSL Co. The batter formulations consisted of wheat flour, salt (1.5% w/w, db), baking powder (0.5% w/w, db), SPI (2 and 4% w/v, db) and Godume shahri seed gum (0.5 and 1%). For all samples, water/dry mix proportion had always been 5:3.Rheological properties of the batters were carried out using a Bohlin rotational Viscometer. For each test, shear rate increased from 0 to 300 s−1. The flow behavior index (n) and consistency coefficient (k) values were computed by fitting the power law model.The chicken nuggets, containing a mixture of chicken breast meat (88%), onions (10 %), Pepper (0.5%) and salt (1.5 %) were prepared in slab shapes using a manually operated cutting device. The dimensions of the chicken nuggets were about 4.5 cm (length) × 2.6 cm (width) ×1.1 cm (thickness) (±0.2 cm). Batter pickups (%) were calculated by the weight difference between the chicken nuggets after coating to the weight of chicken nuggets before coating. Deep frying was performed in programmable deep fat fryer contained 1.5 L refined sunflower oil. Samples were placed in a wire basket and then submerged for the required times of zero, 1, 2, 3, 4 and 5 minutes at 150 ◦C, 170 ◦C, and 190 ◦C. Oil and moisture content of the chicken nuggets were determined by standard techniques. For modeling moisture and oil transfer phenomena in fried chicken nuggets, Fick’s law of diffusion and a first order kinetic model were used respectively.Results and Discussion:Results showed that Godume shahri seedgum had more effect on apparent viscosity compared with soy protein isolates. Polysaccharidic structure of Godume shahri seed gum prepares high number of hydroxyl groups. Hydrodynamic interactions between polar and hydrophobic groups trap most of the free water and consequently increase batter viscosity. All batters showed shear thinning behaviour (n≥0.529). The power law model was adequately suitable to describe the flow behavior of the batters (R2≥0.994). Coating uptake at the surface of nuggets was significantly affected by the batter consistency. The consistency index for batter containing gum was high and therefore the coating uptake was higher for these samples. The maximum moisture loss rate and the effective diffusion coefficient obtained for chicken nuggets coated with only batter. Addition of soy protein isolates and Godume shahri seed gum to batter formulation, decreased the Deff to 3.55-5.46×10-8 m2/s and 3.38-5.32×10-8m2/s, respectively. This can be attributed to the effect of different batter formulations and special functions of gum and protein. The activation energy to remove moisture and oil absorptionwere 10.79 (kJ/mol) and -7.91(kJ/mol) for the control sample, 13.37-17.64 (kJ/mol) and -5.90 to -9.18 (kJ/mol) for soy protein isolates and 11.9-14.7 (kJ/mol) and -7.56 to-10.30 (kJ/mol) for Godume shahri seed gum, respectively.
Hamed Mahdavian Mehr; Arash Koocheki; Mohebbat Mohebbi
Abstract
Introduction: Batter coating is a new technology to reduce fat content of fried foods. The ingredients and flowproperties of batter are the most important parameters to determine the performance of batter coating and quality of the final product. Among batter additives, proteins can be used as an important ...
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Introduction: Batter coating is a new technology to reduce fat content of fried foods. The ingredients and flowproperties of batter are the most important parameters to determine the performance of batter coating and quality of the final product. Among batter additives, proteins can be used as an important and effective component, because of their emulsifying properties, water absorption, and barrier properties. Previous studies have shown that soya protein isolate (SPI) is a very good hydrophilic protein which could be used to control the viscosity of batter. The batter temperature has direct effect on its flow behavior's properties and has a major impact on the quality of final coated product. Therefore, the aim of the present study was to evaluate the effects of temperature (5, 25 and Cº45) and SPI content (2 and 4%), on flow properties of the batter and quality of deep-fried chicken nuggets. Materials and methods:Raw materials such as fresh chicken breasts, onion, salt, hot pepper, wheat flour, baking powder, and 100% pure sunflower oil were purchased from local markets. SPI (92% protein) were obtained from GolharKhorasanRazavi Company. The batter formulations consisted of wheat flour, salt (1.5% w/w, db), baking powder (0.5% w/w, db) and SPI (2 and 4% w/v, db). For all samples, water/dry mix proportion had always been 5:3. Rheological properties of the batters were carried out using a Bohlin rotational viscometer. For each test, shear rate increased from 0 to 300 s−1, followed by a logarithmically decrease from 300 to 0 s−1. The flow behavior index (n) and consistency coefficient (k) values were computed by fitting the power law model, and time dependency properties of the batters were obtained from the area between the upward and downward curves. Temperature dependency of consistency coefficients were assessed by fitting the Arrhenius model. The batter coating on the chicken substrate was appliedat three temperatures (5, 25 and 45 Cº), and batter pickups (%) were calculated by the weight difference between the chicken nuggets after coating to the weight of chicken nuggets before coating. Coated samples were stored at -18 Cº for two weeks. After thawing, chicken nuggets were fried at 180°C for 3 min in sunflower oil using a programmable deep fat fryer. The influence of SPI concentrations and batter temperature on color and crust adhesion of deep-fat fried chicken nuggets was measured with image processing. In brief, images were taken by a digital camera under controlled conditions, and then analyzed by Image J software. The Percentage of adhesion (CRA), obtained by calculating the ratio of the pixels corresponding to the perimeter of the substrate where coating is adhered to the pixels corresponding to the total perimeter of the substrate. The color of deep-fat fried chicken nuggets were examined in terms of L*, a* and b*values. Oil and moisture content of the chicken nuggets was determined by standard techniques. Results & Discussion: Results showed thatall samples had a shear-thinning behaviour at all batter temperatures (n≥0.539). Power law model was adequately suitable to describe the flow behavior of the batters (R2≥0. 994). The activation energy was between 5.106 to 5.630 (kj/mol).Addition of soy protein isolates into the batter, enhanced the time dependency, whereas, the increase of temperature decreased the hysteresis area. The relative increase in apparent viscosity with increasing SPI might be attributed to the high capacity of SPI to absorb free water. However, decrease in apparent viscosity and time dependency of batters with increasing the temperature could be due to the intermolecular interactions in batter system. An increase in temperature weakens the intermolecular interactions and increases the mobility of macromolecules which reduces the batter resistance to shear force. The batter temperature and formulation had significant effect on the batter pickup. This effect was mainly due to the changes occur on flow properties of batter. Using SPI increased the a* and decreased the L* of the final product. This could be due to the active participation of SPI in the Millard reaction. The data obtained for crust adhesion revealed that the increase in SPI concentration lead to a decrease in batter adhesion to the crust. In other words, the ability of soya proteins to form film during early time of frying reduces the moisture migration from the substrate to oil, which creates a positive pressure in the inner layer of crust and reduces the adhesion. Conclusion: Chicken nuggets coated with batter containing SPI had higher moisture and lower oil content than the control sample. Finally, the change in batter temperature had no significant effect on the crust adhesion and oil and water content in the final product.
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.
