Journal of Food Technology and Nutrition
Year:2014 | Volume:11 | Issue:1 (41)|Papers Count:13

Introduction: Lysozyme is a natural enzyme with positive antimicrobial activity against Gram Positive bacteria, but its action is limited on Gram Negative bacteria, which is assumed a restriction for its uses in industry. The purpose of this research was to glycosylate lysozyme with dextran through Maillard-based reaction and to study the antimicrobial characteristics of lysozyme-dextran conjugate.Materials and Methods: Glycosylation of lysozyme with dextran was performed using a 1:5 weight ratio of protein to dextran, incubated at 60oC for one week under the relative humidity of 79%. For evaluating conjugation of dextran to lysozyme, SDS-PAGE electrophoresis was conducted. Gel filtration chromatography with sephadox G-100 was used for separation of conjugated enzyme. Lytic activity, free amino group and antimicrobial activity of the modified enzyme were evaluated.Results: SDS-PAGE electrophoresis was used to follow the glycosylation process. Results indicated that 3.7 moles of dextran were coupled to one mole of lysozyme. The lytic activity of the conjugate was about 62% of that of the native lysozyme. Evaluation of antimicrobial activity of the lysozyme dextran conjugate indicated the effectiveness of modified enzyme against E. coli and a progressive increase in antimicrobial activity with an increase in enzyme-conjugate concentration. The antimicrobial action of lysozyme on S. aureus was not improved by conjugation with dextran as compared with that of E. coli.Conclusion: These results might increase the application of lysozyme as a natural antimicrobial ingredient in different food systems.

Introduction: The interest in probiotic products have been increased recently by the consumers. Milk and dairy products are natural sources of B group vitamins in the human diet. This study was carried out in order to investigate the level of riboflavin (vitamin B2) and niacin (vitamin B3) in probiotic yogurt and the results were compared with the traditional yogurt during refrigerated storage.Materials and Methods: After preparation of conventional and probiotic yogurts, all the samples were stored at 4oC, and the contents of B2 and B3 vitamins were assessed on the first, third and seventh day of refrigeration. Vitamins B2 and B3 were analysed using high-performance liquid chromatography by fluorescence and ultraviolet detections respectively. Data was analysed using SPSS version 18.Results: Vitamin B2 contents of probiotic yogurt samples were significantly higher than the control samples during the course of this study (P<0.05). Significant differences between vitamin B3 contents in conventional and probiotic yogurt samples were found on the seventh day of refrigeration (P<0.05).Conclusion: This study showed that by using probiotic strains higher retention of B2 and B3 vitamins in yogurt during refrigerated storage is observed.

Introduction: Mayonnaise is classified as semi-solid oil-in-water emulsion that contains at least 66% fat according to ISIRI. Due to the risks of too much consumption of oils and fats and diseases related to it, people prefer to decrease the amount of fat in their diet. In this study the application of modified wheat bran as a fat replacer in low fat mayonnaise was evaluated and physicochemical and sensory characteristics of the product was compared with the control sample.Materials and Methods: Mayonnaise samples containing 1, 2 and 3% of dietary fiber with the control (containing starch) were produced. Acidity, pH, viscosity, color measurements, emulsion stability and sensory properties were conducted on all the treatments according to the standard methods.Results: The results showed that after using dietary fiber as a fat replacer in mayonnaise, chemical characteristics such as pH and acidity did not differ significantly as compared to the control. Samples were stable but color created some problems.Conclusion: The results indicated that the mayonnaise sample containing 1% dietary fiber was selected as the best sample as compared to the blank in all the tests performed. The color of low-fat mayonnaise produced was different from the control sample. This might be due to an incomplete function of hydrogen peroxide attributed in vitro.

Introduction: Iran is one of the largest pistachio producer and exporter in the world. Unfavorable environmental storage conditions causes aflatoxin production, moisture absorption, tissue destruction, fat oxidation and undesirable flavor that leads to a drop in the quality of the final product. The aim of this study is to evaluate the anti-fungal and antioxidant properties of chitosan and its impact on the organoleptic characteristics of pistachio nuts.Materials and Methods: Pistachio nuts were prepared and coated with 1% (V/V) acetic acid and chitosan at 0.5, 1 and 1.5% (V/W) concentrations. Acetic acid coated pistachio was used to understand the antimicrobial effect of acetic acid. Pistachio kernels were coated and kept at room temperature (25-27oC) for six months. During storage samples were examined every two weeks for mould and yeast growth and development of Aspergillus, peroxide value, TBA value, moisture and weight changes and sensory characteristics. Experiments were performed in factorial form in a completely randomized design.Results: The results showed that chitosan and acetic acid significantly (p<0.05) inhibited the growth of the Aspergillus. Chitosan reduced the rate of oxidation reactions and by increasing chitosan concentration the anti-fungal and anti-oxidant activities were increased. Chitosan also prevented moisture absorption and weight changes in pistachio nuts. Chitosan at 1.5%concentration had a significant effect (p<0.05) on the flavor of pistachio, but at other concentrations did not affect the flavor. Chitosan did not affect the color, texture and general acceptance significantly (p>0.05).Conclusion: Chitosan was found to be a proper material for coating of pistachio nuts. Chitosan solution at 1% concentration was selected as the best treatment.

Introduction: Although most probiotic foods are derived from milk, the possibility of using other protein rich substrates such as soymilk to make such foods has not been adequately considered. In this study physicochemical, rheological and microbiological characteristics of soy probiotic yoghurt during 21days of storage were evaluated.Materials and Methods: Soy probiotic yogurt was produced by using bifid bacterium lactis B-12 and yogurt culture. Incubation was conducted at 40oC. The ratio of bifid bacterium to yogurt bacteria was 5:1. The produced sample was stored at 4oC for 21 days. Acidity, pH, redox potential, syneresis, viscosity and viability of bifid bacterium lactis B-12 in soy probiotic yogurt were evaluated on 1,7,14 and 21 days of cold storage.Results: The results showed that at the end of storage time, soy probiotic yogurt including bifid bacterium lactis B-12 with yogurt culture has more than 108 cfu/ml bifid bacterium and can be consumed as a probiotic product. This might be due to the slow decline in physicochemical variation and prohibition. This yogurt had favorite rheological characteristics.Conclusion: In this study soy yogurt was produced with probiotic bifid bacteria as a vegetarian product with favorite rheological characteristics.

Introduction: Rice bran is a by-product of rice milling industry that contains considerable quantities of protein, fat, carbohydrate and minerals. According to the chemical composition, rice bran might show suitable physicochemical properties that might have industrial applications.Materials and Methods: In this research protein concentrates were prepared from defatted bran obtained from two varieties of rice (Neda and Tarom) and their chemical composition and physicochemical properties namely protein yield and protein extraction yield, water adsorption index and water solubility index, nitrogen solubility index, bulk density and color parameters were evaluated.Results: Protein yield was in the range of 8.52-8.74(%). Rice bran protein concentrate of Tarom had higher bulk density (0.24 g/g) and protein concentrates had significant differences in some color parameters.Conclusion: It was concluded that rice bran has the potential to be used as an ingredient in functional food formulations to enhance the nutritional values and functional properties of the product.

Introduction: Supercritical fluid extraction (SCFE) is a promising technique that has been attracted by some scientist recently due to the moderate operational condition. Moreover, SCFE products are pure and free of residual solvents. Mathematical modeling of supercritical extraction is a useful tool for deducing the SCF extraction systems, prediction of optimum operational conditions and system design variables, and scale-up to the pilot and industrial scales.Materials and Methods: A new mathematical model modified by Sovova, based on the concept of broken and intact cells, has been applied to understand the variables effect on extraction efficiency in a SCF extraction system. System was made in order to extract the essential oil from orange peel. This model simulates the experimental data points adequately for two separate times using combined pattern of phase equilibrium equations, solute/matrix interaction and internal diffusion rules in the solid particles. Model equations for plug flow are ordinary differential equations and are solved by matlab using numirical method. A number of physical parameters have been determined by experimental data fitting.Results: Extraction curves have been presented on the form of extraction yield versus relative amount of passed solvent. The effect of operational parameters including grinding efficiency, bed void fraction, number of mixers and external mass transfer coefficient have been also investigated.Conclusion: The most desirable result is obtained from grinding efficiency and external mass transfer coefficient of 0.7 and 0.011 respectively, within 20 mixers. The model results present a good agreement with the experimental results. Average absolute deviation between experimental data and the modeling results is about 6%.

Introduction: Crude vegetable oils contain some quantities of Phospholipids. The highest concentration of phospholipids is usually found in crude soybean oil. The presences of phospholipids in the crude and refined oils create undesirable effects on the quality and quantity of the oil during refining operations or use by the consumer. However, if phospholipids are extracted properly from the oil they could have valuable applications in many food systems. There are limited numbers of oil plants that extract soya lecithin in Iran and separate phospholipids from soyabean oil and distribute this valuable by product as soya Lecithin in the market. In this study two dimensional thin layer chromatography has been applied to measure the extracted phospholipids from five varieties of soyabeans both qualitatively and quantitatively.Materials and Methods: Five varieties of soybean cultivated in Iran (Sahar, Sims, Williams, Gorgan3 and Hill) have been studied. The isolated phospholipids for each variety was further separated into their individual constituents using two dimensional thin layer chromatography method and the concentrations were calculated on the basis of the four main phospholipids present in soybean oil that included; phosphatidyl choline, phosphatidyl ethanolamin, phosphatidyl inositol and phosphatidic acid.Results: The amount of total phosphatidies as percent was 1.57, 1.61, 1.72, 1.53 and 1.71% in Sahar, Hill, Williams, Gorgan and Sim varieties, respectively.Conclusion: The results showed that the highest concentration of phosphatidyl choline and phosphatidyl inositol was found in Williams’s variety and the highest amount of phosphatidyl ethanolamin and phosphatidic acid were found in Sahar and Sims varieties.

Introduction: Lemon essential oil is a complex organic compound isolated from the peel that is commonly used as a flavoring agent in food and beverages, cosmetics, and other household products. The aim of this research work is to isolate the essential oil from citrus peel and evaluate its characteristics.Materials and Methods: The essential oil from dry Citrus Limon (Lisbon and Eureka varieties) peel was extracted by hydrodistillation (HD) method. The extraction yield, extraction time, chemical composition of the essential oil, physical constants, energy consumption, and quantities of released carbon dioxides in the atmosphere were investigated.Results: The essential oil yields concerned with Lisbon and Eureka varieties were 1.22±0.14 and 1.18±0.14% (w/w), respectively. There were not significant differences among the physical constants (refractive index, color, and specific gravity) of extracted essential oils from Lisbon and Eureka varieties. Significant differences concerned with energy consumption of both Lisbon and Eureka varieties (0.67 kWh) were not observed. Using GC/MS apparatus, chemical components of extracted essential oils were identified. The major component of extracted essential oils from Lisbon and Eureka varieties was limonene (66.24±4.69 and 59.40±4.20%, respectively).Conclusion: There were not significant differences between quantity and quality of major components of extracted essential oils from two C. Limon varieties.

Introduction: Considering the ever increasing population and industrialization of the developmental trend of humankind's life, one is hardly able to detect the toxins produced in food products using the traditional techniques. This is due to the fact that the quality survey for food products is not cost-effective and even in most of the cases, the precision in the practical techniques like the bacterial cultivation and other techniques suffer from laboratories errors. Hence with the advent of nanotechnology, the design of selective and smart sensors is one of the greatest transformations of the quality control of food products that in few minutes time, and with a very high precision one can identify the toxin level of bacteria. In the present research, the use of the molecular framework polymer of bacterial toxin as the modifier for the improvement of electrochemical properties of PVC film electrode in order to measure the exotoxin is experienced.Materials and Methods: In this technique, the production of molecular framework and polymer is done using Meta acrylic acid monomers, which are formed via covalence connection between Meta acrylic acid monomers (MAA) of white polymer. Here also hydrogenic connection between exotoxin amino acid and Meta MAA is made that would function as the selective absorption for that.Result: The results indicate that the molecular framework polymer sensor is capable of detecting up to the density of 10-3. Additionally, the sensitivity of the sensors was examined up to 60 days and was confirmed for 28 days and then started to decrease.Conclusion: Although the sensitivity of the technique was low but detection precision was perfect. To increase the sensitivity of the test, it is planned to design another technique to increase the sensitivity of the test.