Food Technology
Khadije Sadat Tabatabae; Mohammad Fazel
Abstract
Introduction: Nowadays, lack of time and busy work schedules have led to increase the demand for ready-to-eat foods. Furthermore, as cardiovascular diseases are on the rise in the world including our country, with nearly 40 percent of deaths being linked to these diseases, there is a growing demand for ...
Read More
Introduction: Nowadays, lack of time and busy work schedules have led to increase the demand for ready-to-eat foods. Furthermore, as cardiovascular diseases are on the rise in the world including our country, with nearly 40 percent of deaths being linked to these diseases, there is a growing demand for low-fat products. The main purpose of the deep frying process is to preserve the aroma and flavor of the ingredients in a crispy crust by immersing the food in hot oil. Frying at high temperatures affects the transfer of mass and heat, which causes some of the water to evaporate and be removed from the product, and the oil is moved into the product, replacing the extracted water. This study aims to use methods that reduce the absorption of oil in the fried product, which can reduce health concerns and increase consumer acceptance of the product. Materials and methods: In this study, a day-old chicken breast fillets were used to prepare the samples. The weight of the samples was between 14.5 and 15 grams, with a diameter of 3.7. Coating solutions include aloe vera gel powder at three levels of 1.5, 3, and 4.5 % (w / v) and whey protein concentrate (WPC) at three levels of 2.5, 5 and 7.5 % (w / v), made with distilled water at 25C. Baguette bread was also used to make breadcrumbs. To coat the chicken breast fillet, the samples were immersed in the coating solution (control samples in distilled water) for 1 minute and then placed in breadcrumbs. After preparation, the samples were fried in an automatic fryer at a controllable temperature of 140 C for 6, 8, and 10 minutes, then the samples were cooled to room temperature for 10 minutes and tested for physicochemical properties. The tests included coating, weight loss, moisture content according to the standard AACC method, adsorption of oil by standard method AOAC, tissue measurement test based on the stiffness of the chicken tissue cutting (catching test), and color analysis of chicken samples using CIE Lab colorimetric system through the determination of color characteristics were performed. Results & discussion: The results showed that the coated samples increased the absorption of the coating glaze due to the increasethe viscosity and thus the absorption of baking powder compared to the non-coated sample. The coating with hydrochloric materials based on barrier properties through strong hydrogen bonds between water molecules forms a gel layer with a high water holding capacity that prevents moisture from escaping. This subsequently reduces weight loss. Moreover, due to the inverse relationship between water and oil content, oil absorption was significantly decreased (p<0.01). Among the studied coatings, the highest moisture retention rate and the lowest oil absorption rate are related to the coated sample with 4.5% aloe vera and 7.5% WPC. As the concentration of aloe vera increased, the hardness of the samples decreased, which may depends on the effect of the meat protein to polysaccharide ratio. As the concentration of WPC increased, the stiffness of the samples increased, increasing the sulfhydryl groups, increasing the disulfide bonds in the meat's myofibrillar protein, and thus increasing the tissue stiffness. Increasing the frying time reduced the moisture and increased the oil absorption, weight loss, and stiffness of the samples. The coating reduces brightness due to the presence of various phenolic pigments, especially light- and heat-sensitive anthraquinones in aloe vera and lactose in WPC, and Maillard's reaction at high processing temperatures, resulting in increased browning index and darkening with increasing product color time. This is correlated with the Maillard reaction. Coating with aloe vera gel and WPC is effective in improving the physicochemical properties of fried chicken.
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. ...
Read More
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.
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 ...
Read More
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.
