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Maryam Mohammad Khani; Mohammad Fazel
Abstract
Introduction: Increasing society's desire to consume healthy and low-calorie foods has led to the production of low-fat and healthy foods. In this study, the effect of oil replacement with tofu cheese and Persian gum on physicochemical, textural, rheological and sensory properties of Mayonnaise sauce ...
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Introduction: Increasing society's desire to consume healthy and low-calorie foods has led to the production of low-fat and healthy foods. In this study, the effect of oil replacement with tofu cheese and Persian gum on physicochemical, textural, rheological and sensory properties of Mayonnaise sauce as well as its particle size, were investigated. Tofu was replaced with fat at three concentration levels of 20, 35 and 50% and Persian gum was added to the sauce at three concentrations of 2.5, 3, and 3.5%. The control sample contained 60% fat and guzanthan gum. With increasing tofu, pH and acidity increased and with increasing Persian gum acidity decreased. With increasing tofu, histological test (hardness, adhesiveness, adhesive force, work done to hardness, apparent modulus) decreased and with increasing Persian gum, their increased. With increasing tofu, decreased particle size. With increasing gum until 3%, average of particle size decreased and with more increase of gum, average of particle size increased. The rheological behavior of all samples at a shear rate of 0.01 to 1000 (on second) showed that the viscosity decreased with increasing tofu decreased and with increasing gum, increased. In all samples, with increasing shear rate, the viscosity was decreased, and the behavior of the samples was pyseudoplastic and the parameters followed the power law model. Sample with 20% tofu cheese and 3.5% Persian gum as top samples, whose properties are closer to fatty mayonnaise and can be called Mayonnaise with reduced fat. Materials and methods: Physical and thermal stability tests of the emulsion were performed with a centrifuge machine. PH test was performed using pH meter and acidity test in terms of acetic acid percentages. The fat percentage was performed with a Soxhlet. The texture properties were performed by back extrusion test and the parameters of hardness, adhesiveness, adhesiveness force, apparent modulus and force required to squeeze were calculated. The particle size was measured using a dynamic light dispersion apparatus, and the average particle size, mod, and D50 of the emulsion particles of oil were investigated. The rheological behavior was performed by the rheometer and sensory evaluation was conducted by the hedonic method. Statistical analysis was performed by using SPSS software and the mean comparison test at 5% probability level and in the form of factorial test. Results & Discussion: In the physical and thermal stability test of the emulsion, no two phases were observed in the samples. This could be due to the strong structure of the emulsion and the high viscosity of the continuous phase. By increasing the tofu value, the pH increased, which can be attributed to the decrease in the concentration of hydrogen ion or the increase of the aqueous phase. With increasing amount of gum, there is no change in pH, because the Persian gum has a neutral nature. Increasing the amount of gum did not affect acidity. As the tofu increased, acidity increased, and this increase was very slight, which can be attributed to buffering mode of tofu due to high amounts of high amino acids. By increasing the tofu percentage, the percentage of fat decreases because the percentage of fat in tofu cheese is law and its protein content is much. The increase in gum did not affect the amount of fat, because Persian gum structure was made up of saccharides. The tofu increase up to 35% reduced the texture properties, because the aqueous phase increased, with increasing gum percentage, texture properties increased because it produced a strong gel structure.With the increase in tofu content, the particle size of the oil decreased, because with increasing the amount of fat, the particle size increased. By adding gum the particle size decreased to 3% and then increased, because in the Persian gum structure, there are insoluble branches and the solubility of these branches is low. In the evaluation of rheological behavior, flow behavior test was investigated; viscosity of all samples was reported at shear rates of 0.1, 1, 10, 100/ sec. In all samples, the viscosity decreases with increasing frequency. By increasing the gum at a constant shear rate, the viscosity increased, which can be explained by the fact that the formation of a stronger structure in the presence of higher concentrations of gum. By increasing the shear rate at a constant concentration of gum, the viscosity decreased, and the increase in gum with increasing shear rate also reduced the viscosity and sauce had profit and plastic behavior that could be due to the opening of the bonds. As the tofu percentage increased in all shear rates, viscosity decreased and by increasing the tofu value at a constant shear rate, the viscosity decreased, and the increasing tofu with increasing shear rate reduced viscosity due to high moisture content of the cheese. The rheological parameters of mayonnaise sauce were checked in accordance with the power law. As the gum increased, the consistency coefficient increased , because the number of molecules with high molecular weight in the liquid phase increased, with increasing the percentage of tofu cheese, the coefficient of consistency decreased. The flow behavior coefficient does not have a clear trend, and since it is less than 1, the samples are non-Newtonian. In the strain scan test in lower strains, mayonnaise always has linear viscoelastic behavior. By increasing the gum concentration, both the elastic and viscous components are transported to higher values, which can be due to more interaction between the Persian gum and the components of the emulsion. In the sensory evaluation of the samples, the addition of gum and tofu percentage was not effective.With regarding the data of the tests, mayonnaise sample was identified with the replacement of 20% tofu cheese and 3.5% Persian gum as a superior sample, which its properties are closer to fatty mayonnaise and can be classified as Mayonnaise with law Fat. An extensive medicinal property of Persian gum with tofu cheese in mayonnaise sauce makes it a rich and very good source.
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Farhad Fatehi; Asghar Mahmoudi; Adel Hosseinpour; Hadi Samimi Akhijahani
Abstract
Introduction: Strawberry is one of the native and small fruits of moderate regions, which its cultivation has been increased in all over the world including Iran. Due to the abundance of vitamin C and mineral materials, it is very useful for some diseaseses. Lack of the knowledge in production ...
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Introduction: Strawberry is one of the native and small fruits of moderate regions, which its cultivation has been increased in all over the world including Iran. Due to the abundance of vitamin C and mineral materials, it is very useful for some diseaseses. Lack of the knowledge in production management, harvesting, cooling, transportion, storage, marketing and processing equipments and connection between these different parts are the main problems throgh industrial production of strawberry fruit (Salami et al., 2010). According to the various studies, the parameters such as color, shape, size and mass are not sufficient for the consumer to purchase the fruit (Abbot, 1991). They would like to have more information about the fruit which is supposed to be purchased (Voca et al., 2008). Several researchers have been investigated physical and chemical properties of different varieties of strawberry fruit (Wojdylo et al., 2009; Salamat, 2011; Nemzer et al., 2018). According to the litrature, any international standard classification for Parus strawberry (which is mostly cultivated in Iran) based on physical and chemical was not found. In this study, some physical, mechanical and chemical properties of strawberry fruit Parus variety, as well as the relationship between them, were investigated. The classification was performed based on the appearance features including color and size with the opinion of the expert in six classes. Materials and methods: In Kurdistan province strawberry fruit is often grown in open area and cultivated areas of Parus variety due to many reasons are increasing. To classify the strawberries, six classes were considered. Physical and mechanical properties such as dimensions, density, porosity, stiffness and biological yield point were measured at least at five replications. The porosity of the strawberries was also calculated through the division of the difference between actual and apparent density to actual density. Also, the stiffness and biological yield point were measured using Universal Instron Testing Machine (Zwick/Roll). Chemical properties of Parus strawberry including vitamin C, acidity, total soluble solids and flavor index were investigated at five replications. Results and discussions: The analysis of variance showed that all chemical properties including ascorbic acid, acidity, total soluble solids, and flavor index, were strongly influenced by the class. The LSD mean comparison showed that the highest levels of vitamin C were related to the ripe fruits which had a direct relationship with fruit size. The acidity values between the classes varied from 0.55 to 1.08, and the lowest value was related to the first, second and third classes, respectively. The total soluble solid material (TSS) was affected by some factors: sugar (as main part), organic acid and organic pectins and was increased by growing strawberries and increasing the amount of sugar. For the first, second and third classes, TSS was higher than those of the fourth, fifth and sixth clases. The flavor index value for the lower classes (first, second and third) is higher than the higher classes (almost 2 times). The analysis of variance for all physical and mechanical properties indicated that all parameters are affected by the classes. Due to its more soluble materials, the maximum value for actual density was related to the third and second classes, respectively. The apparent density of agricultural products depends on various factors such as geometric shape, size, surface properties, moisture content and measurement method. The apparent density for the first and fourth classes were 561.743 and 498.408 gr.mm-3, respectively. The maximum and minimum value of stiffness was related to first (about 5.2 N.mm-2) and fourth (about 28.2 N.mm-2), respectively. For biological yield the maximumvalue was related to the fourth class, as well. Conclusion: In this study, the classification of strawberry, variety of Parus was investigated based on physical, mechanical and chemical properties. All properties were affected by changing the classes. The results of this research can be used to design and construct post-harvest and sorting mechanisms of agricultural products which require comprehensive information about physical, mechanical, chemical properties.
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Manoochehr Rashidi; Reza Amiri Chayjan; Ali Ghasemi
Abstract
Introduction: Tomato is one of the most valuable sources of minerals and vitamins supply in the human diet. Low shelf life of tomato and its short shelf life with inadequate processing facilities lead to heavy financial losses. Therefore, preserving and processing of tomato are of the commercial importance. ...
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Introduction: Tomato is one of the most valuable sources of minerals and vitamins supply in the human diet. Low shelf life of tomato and its short shelf life with inadequate processing facilities lead to heavy financial losses. Therefore, preserving and processing of tomato are of the commercial importance. Drying is one of the preferred methods for tomato preservation. Dried tomato products including half tomatoes, tomato slices and tomato powder, have many consumptions, compared with other tomato products. Among dried tomato products, tomato powder has a particular market. Powder production is an alternative method to extend the shelf life of foods. Usually the fruit powder is very dry, humidity absorber and has too much volume. Therefore, during storage, transportation and administration, it requires special care and heavy packaging which increase the cost. To overcome these problems, compression of the fruit powder in tablet form could be a proper solution. Tablet making of fruit powder has gained much popularity due to its ease of use, storage, transportation and product formulation. After the tablet making process, the pills contain high moisture contentwhich makes them un-suitable for transportation and storage. So, in order to prevent the tablets corruption and maintain their quality, tablet drying is one of the important steps after the tablet making process. The drying process is an important operation that affects the quality and final price of the product. Different drying methods play an important role in protecting foodstuffs. However, the effect of different drying methods on the quality of some foodstuffs is not clear. Materials and methods: In this research, after the preparation of fresh tomatoes, the primary moisture content of tomatoes was determined using hot air oven method. Then, using blanching method, the tomatoes were peeled and samples were cut using a sharp razor in thicknesses of 3 mm. Tomato slices were dried using a semi-industrial dryer in a hot air at 50 °C at an air speed of 1 m/s. Dried tomato slices were powdered using a grinder. In order to homogenize the particle size, the tomato powder was sieved by a 50 mesh (Cavity size 0.5 mm) sample. Suitable moisture content to create sufficient adhesion between the particles of tomato powder was selected at %23 d.b. Water and fructose were used as a bonding agent. The process of producing tomato spherical tablets was performed by a hydraulic press. Drying tests of wet compressed tablets were performed immediately after the end of the tabletting process using a hot air drying machine with microwave pre-treatment. In this study, the effect of drying variables,through using of microwave pre-treatment along with hot air, including air temperature in five levels (40, 50, 60, 70 and 80 °C), air velocity at five levels (0.5, 1, 1.5, 2, and 2.5 m/s) and the duration of microwave application at five levels (zero (without microwave), 4, 8, 12, and 16 s) on physical properties (shrinkage and unit density), mechanical (penetration resistance) and thermal (Effective moisture diffusivity and energy consuming drying) of compact pomegranate produced from tomato powder were studied. Statistical analysis of data and optimization of drying process were performed using response surface method and central composite design. Results and discussion: Results showed that effect of air temperature and duration of microwave pretreatment on all variables of compressed tomato tablets were significant in hot air dryers with microwave pre-treatment. Increasing temperature and time of microwave pre-treatment increased the effective moisture diffusivity and shrinkage of the final product. The temperature of the air inlet to the dryer had a negative effect on the resistance to penetration, the unit density and the specific energy consumption of the drying process. Drying under lower temperature conditions and less time for microwave pre-treatment resulted in an increase in the desirability of the drying process
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Hajar Shahsavar; Marzieh Bolandi; Homa Baghaei
Abstract
Introduction: Plant extracts have antimicrobial properties and can be substituted as chemical flavorings in food. Preservatives are compounds that are used to inhibit the growth or to eliminate harmful microorganisms to increase the shelf life of foods. Nowadays, the use of natural preservatives derived ...
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Introduction: Plant extracts have antimicrobial properties and can be substituted as chemical flavorings in food. Preservatives are compounds that are used to inhibit the growth or to eliminate harmful microorganisms to increase the shelf life of foods. Nowadays, the use of natural preservatives derived from medicinal plants is increasing due to their greater compatibility and the presence of volatile compounds (Celiktas et al., 2007). The antimicrobial properties, antioxidant and anticancer effects of these natural additives have been proven (Tajkarimi et al., 2010). In this study, the antimicrobial activity enhancement effect of the combination of hydroalcoholic extracts of basil, cinnamon and salvia on Escherichia coli, Staphylococcus aureus and Saccharomyces cerevisiae yeast in Iranian yoghurt drink (doogh) was investigated for 4 weeks at ambient temperature. Materials and Methods: The milk was boiled in hygienic conditions at 95 ° C for 5 min. After cooling to 45 ° C, they were inoculated. The aerial parts of the studied plants were milled and powdered. Cinnamon, basil and salvia extracts were then soaked. The food strains of Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 700728 and Saccharomyces cerevisiae PTCC 5193 were prepared as lyophilized ampoules. The microdilution broth method was used to determine the minimum inhibitory concentration. The minimum bactericidal concentration (MBC) was determined in accordance with the minimum inhibitory concentration (MIC) results. To determine the antimicrobial effect of the extracts on the yoghurt drink, 9 ml of the prepared yoghurt drink was poured into each test tube. Then 1 cc of each extract and 1 cc of microbial suspension (1.5 × 108 CFU / ml) were added. One tube was considered as positive control (bacteria + yoghurt drink), one negative control tube (extract + yoghurt drink) and one control tube (yoghurt drink only) and the tubes were placed at ambient temperature. Then, on day 7, 14, 21 and 30 during storage, 20 µl of each tube, were cultured on Muller Hinton agar medium and the same amount of yeast was cultured on blood agar medium. After incubation for 24 h at 37 ° C, the colonies were counted. The interaction of antimicrobial activity of the combination of basil, cinnamon and sage extracts was evaluated on the basis of differential inhibitory concentration index (FIC). Results and discussion: The results showed that the minimum inhibitory concentration of the combined basil, cinnamon and sage extracts against Staphylococcus aureus and Saccharomyces cerevisiae and Escherichia coli were 0.4, 0.4 and 3.12 mg / ml, respectively. Also, Staphylococcus aureus was more susceptible to the extracts, which were used alone, and was inhibited by a lower concentration of used extract (Ahmadi et al., 2018). However, due to the maximum minimum inhibitory concentration (MIC), Escherichia coli was less sensitive to the extracts which was used alone. The combined usage of all three extracts significantly reduced the maximum minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), indicating that their antimicrobial activity was more effective against the studied microorganisms than each of the extracts which was used alone. The results of this study showed that synergistic effect against Staphylococcus aureus and Saccharomyces cerevisiae was more effective with the combination of the aforementioned extracts (p <0.05). The results of the Escherichia coli population counting during storage indicated that most of the extracts had a good effect on preventing the growth of Escherichia coli in the doogh environment compared to the control sample (p <0.05). Addition of the extract significantly prevented pH reduction over time (p <0.05), so that the control sample had the highest and the sample containing all three extracts showed the lowest pH changes over time (p <0.05). Therefore, it can be concluded that acid production by Lactobacillus bacteria in samples containing extract during storage period was higher than control. The results of this study were in agreement with the results of Mortazavian et al., (2007) and Voosogh et al., (2009). The acidity of the doogh samples increased significantly over time (P<0.05), while the addition of the extract significantly prevented the acidity increase over time (P<0.05). Sensory properties are the main factors of acceptance and satisfaction of many products. In this study, the mean viewpoint of doogh samples containing the combination of the three above mentioned extracts in terms of taste, odor, color and general acceptance are acceptable. Additionally, it was found that about 90% of participants were willing to use it. Although studies of the overlapping or synergistic effects of medicinal plant extracts in real food environments are not extensive, their results have shown that, the addition of different medicinal plants compounds can increase antibacterial effects. Therefore, the simultaneous use of these extracts can be used in effective control of food pathogens as a complementary method. The results of this study were in agreement with the results of Karimi (2007).
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Hassan Sabbaghi; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad
Abstract
Introduction: Fruits and their products in the dried form are good sources of vitamins, energy and minerals. However, during the process of drying or dehydration there are changes in quality parameters in dried products. Texture is one of the most important quality attributes of fruits during drying, ...
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Introduction: Fruits and their products in the dried form are good sources of vitamins, energy and minerals. However, during the process of drying or dehydration there are changes in quality parameters in dried products. Texture is one of the most important quality attributes of fruits during drying, reflecting their mechanical and microstructural properties. Apple is perishable fruit. Drying of apple is very important because of High losses are experienced during the seasonal glut. A novel process in food industry is the simultaneous infrared dry blanching and dehydration operation (SIRDBD) with intermittent heating method (radiation at constant temperature) exerted on fruits and vegetables that is known to enhance the quality of the final product. In the food industry, end-products must achieve a compromise between several properties, including sensory, sanitary and technological properties. Prediction of changes in texture during drying could be helpful in a better process control and improvement in overall acceptability of a dried snack food. The change of the elastic or viscoelastic texture of the fresh apples to rigid, fragile and brittle in the apple chips were evaluated by instrumental and sensory methods. Many attempts have been made to describe the viscoelastic behavior of dehydrated fruits and vegetables. Maxwell’s or compression models are limited to homogeneous, isotropic materials. In contrast, texture profile analysis (TPA) is more suitable for heterogeneous biological materials and shows a good correlation with organoleptic evaluation. Typical TPA parameters are including hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness and resilience. In this research, for the first time, textural analysis of dried apple slices by infrared heating at different temperatures and different moisture levels was performed. Finally, the optimum texture and overall acceptance of the product are described according to the instrumental analysis. Materials and methods: Apples (Golden Delicious variety) were purchased from a local market and kept in 0°C±1°C and relative humidity ranging from 90% to 95%. Before every thermal processing, the apple specimens were picked up from the cold storage and then they were put into use after reaching the ambient temperature. The samples were skinned manually and then cut into slices with different thicknesses of 5mm, 9mm and 13mm, all 20mm in diameter. The sliced apples were immediately subjected to simultaneous blanching and infrared drying. The texture of dehydrated apple slices using infrared radiation at three surface temperatures of 70, 75 and 80 °C were studied. The product in three thicknesses was dried to achieve a moisture level of 15, 20 and 25% wet weight basis. Then, texture profile analysis (TPA) was carried out to 50% compression strain using texture analyzer. The sensory evaluation of dried slices was also considered for desire texture (Good mouth feels texture, lack of hard tissue, no shrinkage) and overall acceptance (The final acceptability of the product in terms of total sensory properties including color, texture, flavor and aroma) by 10 professional panelists. For statistical analysis, a completely randomized design (CRD) was used in a factorial form (33) and Duncan test with 95% confidence level. Result & Discussion: The results showed that drying to studied moisture levels reduced the hardness and adhesiveness and increased springiness, cohesiveness, gumminess, chewiness and resilience in comparison with raw apple tissue. Hardness of samples dried at higher temperature was higher due to rapid removal of moisture which might have caused collapse of capillary voids inside the product. Due to shrinkage samples became denser and thus a larger fracture force was to be expected. As water content increases (i.e., higher RH) water plasticizes the cell walls and the material and product becomes softer and more pliable, thus hardness decreases. The increase of hardness could be because the rapid mass transfer that damaged the membrane and cell structure of the fruits during drying. Another important factor responsible for the increase of hardness of finish-dried samples is the low final moisture content when compared with other samples. High temperature drying method enables samples to reach low moisture content at relatively short duration and therefore the product with harder texture was obtained. The maximum value of adhesiveness was observed for fresh apples, which could be attributed to the high moisture and sugar content. Adhesiveness decreased with moisture loss, indicating the availability of free water on the sample surface. A significant decrease in springiness following high-temperature drying could be attributed to the glass transition phenomenon and changes from elastic to plastic behavior. In the period of softening, cohesiveness increased with moisture loss. Hardening caused a decrease in cohesiveness depending on the drying temperature. Gumminess is the energy required to disintegrate a semisolid food to a state of readiness for swallowing. High values of gumminess revealed “firm” and “crisp” with a cell rupture mode of tissue failure and lowest values of gumminess could be classified as “soft”. At the end of drying and with apple hardening, chewiness increased to values equal or above initial chewiness, indicating that a larger amount of energy is needed to masticate dried apples. Resilience had increasing with moisture loss. By increasing the thickness of the slices, the cohesiveness and springiness decreased and hence chewiness significantly decreased. The overall acceptance and desire texture in dried samples was observed at lower water evaporation rate conditions (lower temperatures, lower thickness and higher moisture content). In these conditions, the hardness of apple slices tissue was equal to 695.177 ± 7.685 grams. During drying of the apple, textural behavior was varied from the viscoelastic (higher initial hardness, with cohesiveness, springiness and lower resilience) to elastic and then to plastic or glassy.
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Elnaz Shafie; Mohammad Goli
Abstract
Introduction: Milk dessert is a product that contains at least 50% the fresh cow milk or reconstituted milk, which is made with supplementary additives such as flavors, sweeteners, thickeners, and stabilizers, after undergoing heat treatment such as pasteurization or sterilization. Spirulina platensis ...
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Introduction: Milk dessert is a product that contains at least 50% the fresh cow milk or reconstituted milk, which is made with supplementary additives such as flavors, sweeteners, thickeners, and stabilizers, after undergoing heat treatment such as pasteurization or sterilization. Spirulina platensis is a multi-cellular microalgae and a green-blue filament that is a rich source of protein, essential amino acids, essential fatty acids, vitamins, minerals and pigments. Today, as a substitute for sucrose, non-caloric sweeteners are used, which in a small amount make too much sweetness, but they are not absorbed by the body. Of these, stevia with higher sweetness than sucrose (300 to 400 times), less calories and lower glycemia index, is a good herbal sweetener to replace sucrose. Materials and methods: Factor A contains the percentage of algae Spirulina platensis (alternative to milk powder) at 5 levels (0-2 % of the final formula), factor B contains the percentage of stevia replacement with sucrose at 5 levels (0-100), to achieve optimal pudding production formula were selected. Optimization of formula was performed based on the parameters of syneresis, viscosity, hardness and cohesiveness by Response Surface Method (central composite design, α=2 with 6 central points). The results were analyzed using SPSS 20 software and the comparison of the means was done by LSD at 5% level and the charts were drawn by Excel software. Results & Discussion SyneresisGenerally, due to the increase of molecular connections between the chains and the outflow of water from the structure is created. According to the results of Table 3, the independent effect of stevia replacement with sugar, the interaction effect of Spirulina platensis and stevia replacement, and the quadratic effect of each of the independent variables on the Syneresis factor were significant (P <0.05). The rate of syneresis of the samples at higher levels of stevia replacement was reduced by decreasing the percentage of Spirulina platensis replacement, and at lower levels of stevia replacement, with the decrease in the percentage of Spirulina platensis replacement, the amount of syneresis significantly increased. Water holding capacity is linked to the ability of proteins, fats, and dietary fiber to maintain water inside the product structure. Because Spirulina platensis has high levels of protein, dietary fiber and fat, its presence in the formulation of frozen desserts has a significant effect on reducing the product's syneresis. ViscosityAs shown in Table 3, the independent effect of Spirulina platensis replacement and stevia replacement, the interaction effect of Spirulina platensis and stevia replacement, the quadratic effect of Spirulina platensis and stevia replacement on the amount of viscosity was significant (P <0.05 ). The level of viscosity at lower levels of stevia replacement decreased with a decreasing percentage of Spirulina platensis replacement, and at the higher levels of stevia replacement, reducing Spirulina platensis replacement percentage was no significant effect on the viscosity (Fig. 2). In general, the presence of Spirulina platensis in the pudding formulation increased its viscosity, which could be due to the Spirulina platensis protein structure and intercellular interactions. Spirulina with high water absorption reduces water mobility. Also, the presence of fiber and hydroxyl compounds in the structure of this fine algae has a significant effect on the viscosity of the product. Hardness and cohesivenessReplacement of Spirulina platensis and Stevia in pudding formulations did not have a significant effect on the hardness and cohesiveness of texture. While the interaction effect of Spirulina platensis and Stevia replacement on the hardness and cohesiveness of the pudding samples was significant (P<0.001). The quadratic effect of Spirulina platensis and stevia replacement on the amount of hardness and cohesiveness of texture was significant (P <0.05). At lower levels of stevia replacement, by increasing the Spirulina platensis replacement percentage, the hardness of the samples first increased and then decreased, while at higher levels of stevia replacement, with increasing Spirulina platensis replacement percentage, the hardness of the samples first decreased and then increased. Large particles of Spirulina platensis can cause unconnectedness and network connectivity and ultimately create a more sophisticated structure. In fact, Spirulina platensis protein molecules, having a hydrophilic property, compete with other molecules to bind to water molecules, which results in a weaker and more unstable gel structure. On the other hand, tissue hardness is largely dependent on dry matter, the amount and type of protein in the sample. High levels of protein cause cross-linking in the gel network and, ultimately, a rigid and dense structure. But it should be noted that the amount of sample fat plays an important role in the product's texture. Since Spirulina platensis, in addition to protein, also has significant amounts of fat, the intervention of the fatty molecules of this small algae can be effective in forming a weaker gel network and producing soft texture in the product. Finally, optimal formula 1 (2 % Spirulina platensis and 95% Stevia replacement) and optimal formula 2 (0.1% Spirulina platensis and 50% Stevia replacement) were predicted.
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Fatemeh Khodaian; Hajar Abbasi
Abstract
Introduction: Honey is a bee product with appropriate organoleptic characteristics and high nutritional value. Vegetative source, climate conditions, time of nectar collecting, bee specious, and also storage condition of product are effective factors on its quality. During the process and storage stages, ...
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Introduction: Honey is a bee product with appropriate organoleptic characteristics and high nutritional value. Vegetative source, climate conditions, time of nectar collecting, bee specious, and also storage condition of product are effective factors on its quality. During the process and storage stages, chemical reactions such as maillard change the quality and nutritional characteristics of the product. The effectiveness of these reactions depends on various parameters such as primary component’s nature, water activity and pH of product as well as the product storage conditions. Different factors such as, carbohydrate content, enzyme activity, hydroxymethylfurfural (HMF) are introduced as criteria in evaluating qualitative characteristics of honey. HMF is one of the most important factors in this group. It is a consequence of thermal process on foods containing high quantity of fructose and glucose. Therefore, it is considered as an important index on heating and shelf life of this product. In the first step of the present research, qualitative characteristics of four usual Iranian honeys were evaluated. Then, in order to study the effect of storage condition, the quality changes of products at different temperatures and times of storage were investigated. Materials and methods: In the first stage of the present research, qualitative characteristic (fructose/glucose ratio, sucrose, polyphenol content, hydroxymethylfurfuran, moisture, free acidity, lactic acid, total acidity, pH, color, diastase and electrical conductivity) of four Iranian honey (astragalus, ziziphus, citrus and thyme) collected in random sampling were measured. Then, effect of storage temperature (4, 23, 30 and 37°C) on changes of important qualitative characteristic of product (hydroxymethylfurfural content, polyphenol content, pH, color characteristic) were evaluated monthly for six months. Results and discussion: According to results, qualitative characteristics of samples were significantly different since the beginning of storage (p≤0.05). Moisture content of samples varied from 14.5 to 16.5%. PH was found to be 4.38 to 4.94, and total acid content ranged from 6.92 to 16.32%. The highest sucrose content was observed in ziziphus honey and the highest fructose-glucose ratio and pH were observed in astragalus honey. Thyme honey contains the highest diastase activity, acidic compounds, and the lowest amount of moisture and pH and ziziphus honey had the highest amount of acid lactic and electrical conductivity (142/0 mmol/cm). The amount of HMF in ziziphus honey was higher than other kind of samples (28.29 mg/ kg), and the content of these component were lower than 5 mg/kg in astragalus and citrus honey. All of the four samples were in permissible range according to maximum acceptable HMF content based on both Iranian national standard and honey international commission (40 mg/kg). In appearance characteristic, L* (brightness) of thyme and citrus honey were more than others and the highest greenness was observed in thyme honey and the highest yellowness were observed in astragalus and ziziphus samples. In the present study, the polyphenol content of samples was 23.33-39.33 (mg gallic acid in 100 g of sample) and thyme honey contained the highest polyphenol content. Diversity in floral is one of the main reason for differences in the qualitative characteristic of samples. Changes in mineral content, phenolic components, and floral origin were considered as the main effective factors in color changes of honey types. Storage condition and honey type had significant effects on qualitative characteristics of product. Increasing time and storage temperature reduced brightness and hue angle, and increased chroma index in all kind of honey. By increasing the temperature and storage time, undesirable HMF content of samples were increased. Among the studied conditions, the best storage temperature in control of HMF content of product was 4 °C. Increasing storage temperature and time decreased the phenolic compounds of samples until the third month, and after that it was increased. In this regard, the effect of higher temperature on increasing polyphenol contents of product was more obvious. This observation is a consequence of secondary compounds formations from browning process in the product. Evaluating correlation among different parameters showed that, there were a positive significant correlation between HMF content with polyphenol compounds (r= 0.738), a* (r= 0.8868) and chroma index (r= 0.373) (p<0.05), and there were a negative significant correlation with brightness of appearance (r= -0.853) and hue angle (r= -0.858) of product at a level of 0.05. Also there were observed positive and significant correlation among polyphenol content of product with a* (r= 0.65) and chroma index (r= 0.298) and also negative and significant correlation with brightness (r= -0.655), hue angle (r= -0.651) and ph (r= -0.258). Therefore, honeyes with more redness and less brightness usually contain higher polyohenol which their participation in Millard reaction is the main reason for higher content of HMF in these samples. Therfore, determining suitable condition and storage time of honey according to their different primary characteristic should be considered in order to protect qualitative characteristic of product.
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Seyed Hassan Jalili; Reza Farhoosh; Arash Koocheki; Abbas Ali Motallebi
Abstract
Introduction: Considerable amounts of essential fatty acids in fish oil makes it possible to use in the production of functional foods to meet nutritional needs and beneficial effects on health. One of the major problems is their high susceptibility to oxidative deterioration and consequent production ...
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Introduction: Considerable amounts of essential fatty acids in fish oil makes it possible to use in the production of functional foods to meet nutritional needs and beneficial effects on health. One of the major problems is their high susceptibility to oxidative deterioration and consequent production of undesirable flavor. At present, some synthetic compounds are used as antioxidants in food and biological systems, but the use of synthetic antioxidants is of concern due to their potential health hazards. Therefore, the use of natural antioxidants in foods is the first choice. Enzymatic protein hydrolysis has been applied to food industry by-products to produce foods with enhanced functional properties. Antioxidant and antiradical activity of protein hydrolysates from meat, skin, bone, viscera and roes of various aquatic species has been reported. Silver carp (Hypophthalmichthys molitrix) skin (SCS), as low price by-product from minced products processing plants is available in I.R. Iran. Amino acids composition and sequencing determines the functional properties of peptides, which depends on the source of protein, the method and conditions of preparation and molecular weight distribution of resulting hydrolysate. The enzyme type and hydrolysis conditions, including enzyme/substrate ratio, temperature, time and pH, can affect the peptides length and functional properties of protein hydrolysates. The effects of hydrolysate from SCS hydrolyzed by alcalase on some quality features and oxidative stability of microencapsulated Kilka (Clupeonella spp.) oil at pH 6.8 and 3.4 were investigated. Materials and methods: SCS was pre-treated with NaOH and acetic acid, washed and freeze dried. Proteolysis with alcalase (1% w/w) at 50 ºC, without pH adjustment, was performed for 4 hours with gentle stirring. Enzyme inactivated by placing the sample in a boiling water bath for 15 minutes. After centrifugation at 13000 g for 20 minutes, supernatant was removed as silver carp skin hydrolysate (SCSH) and freez dried. Emulsions were prepared with 31.25% dry material. 25% of wall materials (equal proportions of maltodextrin and Hi-Cap®100), fish oil 25% and SCSH (for preparing 1, 2, 3, 4 and 5 mg/mL treatments) in two adjusted pH 3.4 and 6.8, was used. Fish oil was refined using multi-layered column chromatography (alumina-silica gel), and fatty acid composition was determined. The emulsion pre-homogenized by the IKA Ultra-turrax at 15,000 rpm for 2 minutes and finally by a HSTO homogenizer at 350 bar for 5 circle, to produce microemulsion. Effects of treatments on the characteristics and oxidative stability of microencapsulated Kilka oil for 28 days in the dark at 45 ºC were compared by determination of surface oil, microencapsulation efficiency, free oil, emulsion stability (%separation), droplet size, optical microscopic observation of morphology and peroxidation stability. Results & discussion: Results showed significant differences between proximate composition of silver carp skin, before and after pre-treatment and revealed that applied method and conditions reduced the amounts of oil and ash to an acceptable level. No aggregation and cluster formation was observed in optical microscopic images of prepared emulsions. The effects of pH on the droplet size and microencapsulation efficiency were insignificant (p> 0.05), but the amount of free oil and emulsion stability were significant at ≥2 mg/mL concentrations of hydrolysate (p<0.05). Peptides effectively retarded the preoxidation of Kilka oil in the model system. Hydrolysate antioxidant power was dose dependent. Peroxidation trends were nonlinear for control and 1-4 mg/mL treatments. These trends continued linearly, with mild slope for 5 mg/mL, and was similar for 2 pH during 28 days. Hydrolysate of SCS may be used as a natural antioxidant for the production of stable microencapsulated fish oil for the enrichment of various kinds of beverages with a wide range of pH.
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Fakhri Shahidi; Farideh Tabatabaei Yazdi; Majid Nooshkam; Zahra Zareie; Fereshte Fallah
Abstract
Introduction: Lipid oxidation leads to the generation of off-flavors and potential toxic compounds. Synthetic antioxidants are frequently applied for inhibiting this reaction, however; there is a concern regarding to the potent toxic effects of synthetic antioxidants on human health. The non-enzymatic ...
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Introduction: Lipid oxidation leads to the generation of off-flavors and potential toxic compounds. Synthetic antioxidants are frequently applied for inhibiting this reaction, however; there is a concern regarding to the potent toxic effects of synthetic antioxidants on human health. The non-enzymatic glycosylation reaction (Maillard reaction) has been broadly used to ameliorate the biological and functional features of proteins and polysaccharides. The Maillard reaction produces products with versatile functions such as antioxidant, antimicrobial, antihypertensive, anti-browning, and prebiotic properties. In this regard, the Maillard reaction products (MRPs) can be used in the food industry to inhibit the oxidation reaction due to their superb antioxidant effect. In this study, chitosan was glycosylated with inulin, fructose, and glucose. Chitosan is a chitin derivative with cationic nature having antimicrobial, antioxidant, metal chelation, and film-forming features. Inulin is recognized as a prebiotic sugar with vast applications in food and pharmaceutical sciences. The purpose of this study was to chemically modify chitosan through the Maillard reaction in order to boost its antioxidant and antimicrobial properties. Materials and methods: Chitosan (0.5% w/v) was dissolved in 1.0% v/v acetic acid solution followed by stirring for 1.0 h at room temperature. Afterwards, sugars inulin, glucose, and fructose were separately added to the chitosan solution at final concentration of 1.0% w/v. The obtained solutions were then stirred until complete sugar dissolution. The pH of solution was adjusted to 6.07 by adding 2.0 M sodium hydroxide and then the chitosan-sugar Maillard conjugates were fabricated through autoclaving the solutions at 121 °C. Changes in pH after the reaction were measured using a pH meter. The extent of the Maillard reaction was estimated via measuring the absorbance of the conjugated solutions at 294 nm (the intermediate products) and 420 nm (final products). Fourier transform infrared (FTIR) spectroscopy at transmission mode and 400-4000 cm-1 was employed to evaluate the structural changes of chitosan upon conjugation. Antioxidant activity of the conjugates was evaluated based on the reducing power assay. One mL of the samples was charged with 1.0 mL of distilled water and 1.0 mL of potassium ferricyanide (1.0% w/v). The solution was mixed and incubated at 50 °C for 20 min. After adding 2.5 mL of tri-chloroacetic solution (10% w/v), the obtained solution was centrifuged at 5000 g for 5.0 min. Afterwards, 2.0 mL of the supernatant was mixed with 2.0 mL of distilled water and 1.0 mL of ferric chloride (0.1% w/v). The solution was stand for 10 min at ambient temperature and then its absorbance was recorded at 700 nm. Antimicrobial effect of the conjugates against pathogenic microorganisms (E. coli, S. aureus, B. subtilis, P. aeruginosa, A. niger, and C. albicans) was measured according to the minimum inhibitory (MIC) and microbiocidal (MBC) concentrations. SPSS software (version 21) and one-way ANOVA were applied for data analysis. Duncan’s multiple range test was employed to determine the differences between means. Results & discussion: The Maillard reaction led to a significant decrement in pH value of chitosan-saccharide systems, mainly due to the covalent coupling of amino groups of chitosan to carbonyl groups of reducing sugars in conjugation with the production of acetic and formic acids. The highest intermediate compounds (A 294nm) and lowest browning intensity (A 420nm) observed in chitosan-fructose conjugate, which was likely attributed to the lower reactivity of fructose. Chitosan-inulin conjugate presented the highest A 420nm and lowest intermediate-to-final ratio (A 294nm/A 420nm), probably due to the lower inulin molecules and subsequently carbonyl groups compared to fructose and glucose. These groups may react with amino groups of chitosan at initial reaction times, leading more conversion rate of the intermediate compounds to the final ones. FTIR spectra of the chitosan and conjugates revealed that absorbance peak at 1661 cm-1 in chitosan spectrum decreased and shifted to 1578 cm-1 (in chitosan-fructose conjugate), 1579 cm-1 (in chitosan-glucose conjugate), and 1580 cm-1 (in chitosan-inulin conjugate), indicating the stretching C-N group and -C=N group and the formation of Schiff base (-C=N) between reducing end of the saccharides and amino groups of chitosan. Reducing power of the chitosan-saccharide systems improved after the thermal process. Although, chitosan-glucose and chitosan-fructose conjugates had significantly higher reducing power than unconjugated counterparts, but chitosan-inulin conjugate showed non-significantly improved antioxidant activity compared to its non-heated mixture. Antioxidant activity of the Maillard conjugates was ascribed from the electron donating ability of their hydroxyl and pyrrole groups. The conjugates had lower MIC and MBC in comparison to their unconjugated pairs, except for chitosan-glucose conjugate, which showed no differences in MIC and MBC compared with its non-heated mixture. Antimicrobial property of the Maillard products, especially melanoidins has been attributed to their metal chelating features; melanoidins exert a bacteriostatic effect at low concentration and bactericidal effect at high levels through sequestering ionic iron from medium and magnesium from outer membrane, leading to the cell membranes destabilization. Additionally, antioxidant capacity, high surface activity, and inhibiting effect towards catabolic enzymes have been reported as another antimicrobial mechanisms of the Maillard products. In general, it can be concluded that chitosan-saccharide Maillard-based conjugates, particularly inulin-chitosan one could be used in the food sector as a novel prebiotic-based active bio-compound with antioxidant and antimicrobial features.
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Zhaleh Sadat Ladjvardi; Mohammad Saeid Yarmand; Zahra Emam-Djomeh; Amir Niasari-Nasalji
Abstract
Introduction: In recent decays, consumers have more information about foods. Vegetables, crops and other natural food with high nutritional value replace hazardous substances. In this study, the effects of locust bean gum and xanthan gum with β-glucan were investigated in camel synbiotic yogurt ...
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Introduction: In recent decays, consumers have more information about foods. Vegetables, crops and other natural food with high nutritional value replace hazardous substances. In this study, the effects of locust bean gum and xanthan gum with β-glucan were investigated in camel synbiotic yogurt functional. Locust bean gum (LBG) has about 88% of galactose and mannose, 4% other polysaccharides, 6% protein, 1% cellulose and 1% the ashes (Nasirpour, 2013; Hansen, 1993).Xanthan gum is an extracellular polysaccharide produced by Compestris Xanthomonas in aerobic fermentation process. Xanthan reactions synergies with guar and LBG, so the low concentrations in the presence of LBG viscosity increase (Ramirez-Figueroa et al., 2002).In this study, the oats β-glucan inoculated with probiotic bacteria to camel milk for production of functional synbiotic yogurt was employed. The camel milk has high nutritional value such as insulin-like substance, less lactose, immuno-globulins and lactoferrin, antioxidants and antimicrobial agents and other nutrients (ladjevardi et al., 2015; Niasari Naslaji et al., 2011). Synbiotic dairy product made from combinations of probiotic bacteria with prebiotics agent (β-glucan). About 108- 107 cfu/mL of live bacteria should be in the final products (Faraj et al., 2012). β-glucan is an indigestible carbohydrate complicated (Theuwissen & Mensink, 2008) with very high nutritional properties, including improved intestinal activity (fibers), lowering uric acid blood, stimulating the immune system (Xue et al., 2013; Chao et al., 2013). Materials and Methods: At first, camel milk (from Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Iran) was standardized by centrifugation (Universal 320, Hettich, Tuttlingen, Germany) to 1.9% fat content. Then xanthan gum and locust bean gum (1:1) were added in three level 0.1, 0.2 and 0.3%. β-glucan (extracted from oats as described by Moura et al. (2011() in 1.5, 2 and 2.5% levels was added to milk. Camel milk was homogenized with ultra-turrax blender (T25, IKA, Staufen, Germany) in speed 9000 r.p.m. Then, the milk sample was pasteurized for 15 min at 75±1 °C. Samples were prepared by adding yogurt starter culture (1.5%) containing probiotic microorganisms (ABY1, Cristian Hansen, Hørsholm, Denmark) at 42 °C. The mixtures were redistributed into 50 mL sterile plastic cups, incubated at 42 °C until their pH decreased to 4.6, they cooled and stored at 4±1 °C ( Mazloomi et al. 2011). Determination of water-holding Capacity (WHC)5 g of yogurt was centrifuged (Mikro 220R, Hettich, Tuttlingen, Germany) at 4500 r.p.m. for 30 min at 10°C. After centrifugation, the supernatant was removed and the pellet was collected and weighed. Microbial Analyses1 g of yogurt with 9 mL of normal saline (a solution of 0.9 % (w/v) NaCl ( Merck, Darmstadt, Germany)) was mixed and diluted to a concentration of 106 and 107, and then 1 mL of each dilution was repeated in 2 plate containing the MRS-Agar (Merck, Darmstadt, Germany) with 0.15% Bovin-Bile (Sigma-Aldrich, Louis, MO, USA). Bacteria were counted by the pour plate technique. The plates in duplicates were incubated anaerobically at 37 °C for 72 h, after this period, colonies were counted (Mishra and Mishra 2012). Statistical AnalysisThe response surface methodology (RSM) and ANOVA (p<0.05) were used for data analysis using Design Expert 8 (Version 8.0.7.1, Minneapolis, MN, U.S.A) software. The experiment was designed according to central composite design (CCD). All experiments and measurements were conducted in triplicate, mean value ±sd are reported. Result and discussionWater-Holding Capacity (WHC)Changes of xanthan gum, LBG, β-glucan and time storage have a significant effect on the WHC. Increasing the percentage of LBG, xanthan gum and the percentage of β-glucan significantly increased the WHC. Time storage reduced the WHC similar results of Ladjevardi et al. (2015) and Sahan et al. (2008).According ANOVA table, the products had maximum water holding capacity at the highest percentage of LBG and xanthan gum. The percentage of xanthan gum and β-glucan increased water holding capacity. These factors (LBG and xanthan gum, xanthan gum and β-glucan) have a synergistic effect on each other mutually.Xanthan gum and LBG showed interaction effect with time storage on changes in WHC including maximum water retention in the sample tissue, the high percentage of gums and the early days of production. Viability of probiotic bacteriaViability of probiotic bacteria significantly increased when used from high percentage of β-glucan (as a prebiotic agent) in synbiotic yogurt. This change was related to increasing food for probiotic bacteria (Kearney et al., 2011). According to the results mentioned a good environment for the growth and activity of the microorganisms (ladjevardi et al., 2015). The unfavorable conditions in production of synbiotic yogurt, was time duration. During storage, the number of probiotic bacteria that are present in the product is reduced Xanthan gum and LBG have no significant effect on viability of probiotic bacteriaXanthan gum and time storage have interaction effect on the viability of probiotics bacteria. As expected, the best conditions for probiotic bacteria to maintain a high percentage of xanthan gum was at the early days of the sample production ((Norton and Lacroix, 1990; Sanderson, 1990).According to the results, it was found that gums such as xanthan gum and LBG showed similar results to those of El-Salamt et al. (1996) and Hematyar et al. (2012) and had adverse influence on the growth and activity of beneficial bacteria.
Short Article
Omid Doosti Irani; Abbas Rohani; Mahmood Reza Golzarian; Mansoureh Shamili; Peyman Azarkish
Abstract
Introduction: The diversity and abundance in quality properties of agricultural products are leading factors to develop non-destructive methods. Machine vision and artificial intelligence are powerful techniques in detection of many physical, mechanical and chemical properties of agricultural products. ...
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Introduction: The diversity and abundance in quality properties of agricultural products are leading factors to develop non-destructive methods. Machine vision and artificial intelligence are powerful techniques in detection of many physical, mechanical and chemical properties of agricultural products. Prior to exporting, fruits are sorted in terms of their shapes, volumes or weights. Non-destructively taste-based sorting can be of importance in terms of markability and application. Artificial Neural Network (ANN) has been introduced as a new method to predict quality parameters such as firmness, total sugar content (TSC) and pH of agricultural products and to grade the products accordingly. Material and Methods: In this research, the quality properties of Mango (Kelke- Sorkh var) were predicted using the combination of image processing and artificial intellect techniques. The mango samples were harvested from the orchard in Minab, Hormozgan province in Iran. The samples were transferred to computer vision lab, room temperature of 24°C and 22% RH. The samples were divided into three groups for temperature treatment. They were kept at three temperature levels of 5°C, 15°C and 24°C (control group) for 48 hours. The sample were then placed in room temperature and were imaged every second day for 14 day period. After imaging, each sample was undergon destructive tests for determining their quality attributes including sugar content, firmness and pH. The images were taken by a digital camera in visible spectrum (Nickon Coolpix p510, Nikon Inc, Japan). The taken images were, then, transferred to Matlab software environment (Mathworks Inc, US) for analysis and processing. The color factors from regions of intrest were extracted from the images in L*a*b* color space. The segmentation of images was performed by thresholding (threshhold value of 0.3) the image of difference between red and blue channels of taken RGB images. The conversion of RGB color space to L*a*b* was done by converting RGB image to XYZ basic color space first and before converting X, Y, and Z basic color components to L*, a*, b* color factors. The L* represent the lightness in the image from black (0) to white (100). In this project, a multilayer perceptron neural network with a hidden layer was used. The optimum number of neurons in the hidden layer was found to be 25. The maximum iterations was set as 1000 and the learning rate was set as 0.001. Results and discussions: The input variables to the network were temperature treatment at three levels (control, 5°C and 15°C), the color factors (L*, a* and b*) and the variations of three color factors across the regions of interest (standard deviations of L*, a* and b*). The output variables were sugar content, pH and texture firmness. The results showed that the accuracy of the ANN model on the prediction of pH, sugar content and firmness were 45%, 85 and 88%, respectively. Although the accuracy of ANN model for predicting pH from color factors was rather low, this model was able to predict firmness and sugar content with highly accurately. The histogram of errors among three ANN models also showed the ANN model for predicting firmness and sugar content performed better than that for predicting pH. The MAPE prediction error were 9.53, 22.74 and 6.14, respectively, for predicting firmness, pH and sugar content. Comparing the results from the network in training and testing stages showed that ANN can be considered as a reliable method for estimating quality factors of firmness and sugar content with high accuracy and estimating pH with rather non-applicable accuracy.
Short Article
Zahra Eskandari; Seyed Ali Jafarpour
Abstract
Introduction: Gelatin is a water-soluble protein mixture that is obtained by partial hydrolysis of collagen, which forms the major protein in bones, cartilage, and skin. Gelatin is made from collagen fibers, which is low in protein, cholesterol, fat and carbohydrates, with a special positive effect on ...
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Introduction: Gelatin is a water-soluble protein mixture that is obtained by partial hydrolysis of collagen, which forms the major protein in bones, cartilage, and skin. Gelatin is made from collagen fibers, which is low in protein, cholesterol, fat and carbohydrates, with a special positive effect on human health. Gelatin is one of the most notable natural biopolymers, the most important source of this hydrocolloid is pig. Trying to find suitable gelatin supplements for food products is increasing. Fish gelatin is one of the most suitable mammalian gelatinous substitutes and is accepted as a Halal (Kosher) food item. The purpose of this study was to extract gelatin from sturgeon Beluga skin using pepsin enzyme and then investigate the effect of the enzyme on the improvement of physiochemical and its functional properties in comparison to the gelatin extracted by chemical method. Material and Methods: Pre-treatment and extraction of gelatin and application of factorsSkin Preparation was performed according to Feng et al. (2013) with slight changes in pre-treatment steps. A solution of 3.5% NaCl was used to remove non-collagenic proteins and 0.5% sodium carbonate solution (Na2CO3) to remove lipid from the skin. The initial pretreatment was carried out with a solution of 3.5% sodium chloride at a rate of 1:10 w / v at a speed of 180 rpm for 6 hours which was replaced every 3 hours with the water. Extraction by was carried out following Tong et al. (2013) method. Gelatin was obtained from pre-treated skin in distilled water at temperature of 30, 40 and 50 degrees Celsius and a percentage of enzymes (0.01, 0.055 and 0.1) at different pH (2, 3 and 4) for 6 hours and 45 minutes in hot water bath. Then, the mixture was kept in the boiling water bath, for 5 minutes to inactivate the enzyme. The solution was passed through a cleaning cloth and then centrifuged at 3500 rpm for 20 min and finally was lyophilized in a freeze-drier. In this research, the Response surface methodology response (RSM) method was used to optimize the experimental treatments. The central composite rotatable design was used to optimize the gelatin enzyme extraction process. Results and Discussion: The α chains were clearly visible in the sample extracted by the enzyme, with molecular weight of 130 kDa (treatment 5), while the α2 chain is much weaker in the extracted gelatin by chemical method. By decreasing enzyme ratios, chains with molecular weights of less than 130 kDa disappeared gradually in chemical samples as well as in an enzyme-extracted sample (treatment 19). The gelatin extracted by the enzymatic method contains α1 and α2 chains. In the average amount of enzyme (treatment 17), the α2 chains were relatively weaker than the maximum value of the enzyme (treatment 5), and these chains almost disappeared in the minimum amount of enzyme (treatment 19). These chains are weaker in the chemical extracted gelatin than that of treatment 5. Moreover, it can be seen that in the gelatin extracted by the enzymatic method, the ratio of the α2 / α1 chain is about 2 (the intrinsic ratio in collagen I), which shows that the inherent structure of gelatin is preserved.The highest and lowest amidic wavelength A was obtained for treatment 17 and treatment 19, the highest and lowest wavelength amide I for treatment 5 and treatment 19, the highest and lowest amid II wavelengths for chemical extracted treatments and treatment 17, The highest and lowest ratio of amide III to amide 1454 is related to treatments 5 and 19, and the highest and lowest amount of amide B is related to treatment 19 and 5.The behavior of the viscoelastic modulus of the treatments extracted with the pepsin enzyme (treatment 5, 17 and 19) and the chemically prepared sample showed that at temperatures lower than 20 ° C the storage or elastic modulus (G ') and the loss or viscous modulus (G') decreased with increasing temperature and the elastic modulus was larger than the loss modulus (G' >G'' ) indicating that the samples are still jelly-like (with the exception of treatment 19 that had the weakest gel strength).In all gelatin samples extracted using pepsin and chemical method, first, a relaxation stress index (viscosity increase at the beginning of the graph), and then a thinning non-Newtonian behavior (pseudo-plastic) was obvious during the shear rate. In fact, in the behavior of pseudo-plastic, the viscosity of the fluid is related to the shear rate and has decreased with increasing shear rate. Non-Newtonian viscosity of treatments prepared by the enzymatic method (except treatment 19) was higher than that of the chemically prepared sample at different applied shear rate.
