جستجوی مقالات مرتبط با کلیدواژه "الکتروفورز" در نشریات گروه "صنایع غذایی"

 High levels of free radicals can damage biomolecules and eventually cause oxidative stress. Bioactive peptides produced during enzymatic hydrolysis keep high health properties, such as antioxidant properties. The production of antioxidant peptides has received much attention as a new generation of natural antioxidants. Plants are one of the most abundant sources of biopolymers, especially protein. As long as the protein structure is intact, its amino acid sequence is inactive; however, during proteolysis, fermentation, and gastrointestinal digestion, these amino acids are released as oligopeptides ordinally with less than 20 amino acids and below 10 kDa in molecular weight. These peptides are more digestible and can exhibit specific bioactive properties such antioxidant properties. In this regard, the use of food waste containing protein to produce bioactive peptides and increase their value has received increasing attention. Enzymatic hydrolysis can increase their functional properties by converting proteins into peptides without affecting their nutritional value. Pomegranate seed protein is a by-product of the pomegranate seed oil industry and can be a good source of bioactive peptides with antioxidant properties. According to our knowledge, there isn’t any data about the enzymatic hydrolysis of pomegranate seed protein for antioxidant peptides production. In this study, the optimal conditions for enzymatic hydrolysis of pomegranate seed protein with trypsin using the responses surface method and the effect of hydrolysis on protein structure were investigated.

 In this study, the protein was extracted from pomegranate seed, and using trypsin the optimization of enzymatic hydrolysis conditions of protein was determined by Face-Centered Central Composite design, which is one of the responses surface design methods. The effect of independent variables including temperature (30 to 45 °C), time (30 to 180 minutes), and enzyme to substrate ratio (1 to 3 w/w) on DPPH free radical scavenging activity and Fe+3 reducing power as responses, was evaluated. Validation tests were performed for confirmation of the proposed values by software and the degree of hydrolysis of the samples was determined. In the next step, the unhydrolyzed and hydrolyzed protein was evaluated for molecular weight distribution and their surface hydrophobicity was compared. Finally, scanning electron microscopy images were used to confirm the hydrolysis process.

 Under optimal conditions obtained from the response surface method (temperature: 37.6 °C, time: 136.55 minutes, and enzyme to substrate ratio: 2.2%), trypsin-derived hydrolyzate, showed DPPH free radical scavenging power: 87±0.89% and Fe+3 reduction power: 0.293±0.44. Under these conditions, the degree of hydrolysis was equal to 30.1±1%. The optimum conditions of hydrolysis were validated by RSM. The increase in the surface hydrophobicity of the protein after the hydrolysis process indicated the unfolding of the pomegranate seed protein chain and the exposure of its structure during the reaction. The electrophoretic profile of denatured pomegranate seed protein showed smaller peptide bands and lower band intensity, along with losing some of the peptide fractions after hydrolysis. so the efficacy of trypsin at cleaving the protein was confirmed. Evaluation of images obtained by scanning electron microscopy showed that unhydrolyzed protein had complex structures comprised of random sheets of different sizes and shapes and the protein degraded into small fragments and looser structure with many folds after enzyme hydrolysis, resulting in smaller particles compared with untreated samples with the same SEM parameters

Considering the consumer’s tendency toward functional foods and present concerns about the application of synthetic additives and according to the results, the hydrolyzed pomegranate seed protein prepared by trypsin shows good antioxidant capacity. In addition, there will be a reduction in waste generated by the pomegranate processing industry. Further studies will need for the isolation and identification of the specific peptides and amino acid sequences and the evaluation of their possible incorporation in food matrices.

Application of lysozyme as a natural antimicrobial or preservative agent in food and pharmaceutical industry is well known. The antimicrobial effects of lysozyme can be expanded by conjugation with carbohydrates via Maillard reaction, however this natural reaction is a time consuming process. So in this study a new method microwave heating, was applied to Accelerate the Maillard reaction. Lysozyme was mixed with dextran and heated by microwave irradiation. The glycation extent was determined by SDS-PAGE electrophoresis, cation-exchange chromatography and sugar analysis. SDS-page pattern show that with increasing heating time a high molecular weight conjugates were appeared and maximum glycosylation was occurred after 4 minutes heating. The elution profiles (chromatograms) of the lysozyme–dextran conjugates compared the natural lysozyme showed that the conjugated peak shifted towards the higher molecular weight fraction and overlapped with the non conjugated proteins, indicated that lysozyme was covalently bound to dextran. These results suggest that Maillard reaction rate can be increase using microwave heating.

Engineering of food proteins with improved functional properties and higher resistance to heat is the main goal of food scientists. Food technologists are always seeking for innovative, simple and effective methods to manipulate proteins, hence natural modification has had the most attention in last decades. One of the natural ways used for protein modifications isMaillard grafting reaction. Maillard reaction as a consequence of covalentbindingbetween the available amino groups of the proteins and carbonyl containing moiety of the polysaccharides, causes a loss in free amino group content of the mixture that can be measured through different methods. Protein-polysaccharide hybrids, as a result of dry heating of two biopolymers mixture under controlled reaction conditions, cause the emergence of conjugates with novel functionalities.Selecting appropriate reaction conditions has a significant impact on the properties of the final conjugates. Among the factors affecting the degree of conjugation, temperature, pH and incubation time have considerable roles in determining the degree of conjugation. There are various methods by which conjugation degree can be assessed and factors such as accuracy, cost, accessibility and etc. must be considered when selecting a measuring method. Therefoe, in this study the effect of different Maillard reaction conditions on the conjugation degree of soy proteins-dextran heated mixtures have been investigated. In addition, the glycation degree was compared and reported by both OPA assay and UV absorbance methods.
Soy proteins–dextran conjugates were prepared as described later. First, soy proteins and dextran were mixed with phosphate buffer (0.1 M, pH: 8.5 and 7) and 1 to 4 ratio of protein to polysaccharide. After mixing and incubating at ambient temperature for some hours, solutions were frozen at –80 ℃ and freeze dried. Then, the lyophilized powder was incubated at 40 ℃ for 0, 4, 8, 24 hours and 2, 4, 6, 8, 12 days, at 60 ℃ for 0, 1, 2, 3, 4, 6, 8 days and at 80 ℃ for 0, 1, 2, 4, 8, 16, 24, 48 hours, under the 79 percent relative humidity in presence of saturated KBr. For each treatment a non conjugated sample was prepared in the exact same condition. Conjugation of proteins to polysaccharides was monitored by two methods (OPA assay and UV absorbance). Determining degree of glycation by OPA method was done as follows, in this procedure the level of available amino groups was estimated using the ortho- phthaldialdehyde (OPA) reagent, the absorbance was measured at 340 nm and degree of glycation was measured using a formula. To investigate the UV absorption of conjugated proteins, the samples were diluted using distilled water and the absorption was read using a UV-visible spectrophotometer.
Covalent linkage between amino group of proteins and carbonyl group of polysaccharides causes depletion in the amount of available amino groups. The extent of soy proteins-dextran conjugation under various Maillard reaction conditions was evaluated by the reduction of available amino groups of proteins, the more reduction in amount of amino groups, the more conjugation between protein and polysaccharide. OPA results showed that, in the samples heated at 40 °C and 80 °C (at both pH 7 and 8.5), the amount of free amino groups slightly reduced compared to 60 °C heated samples. The disappearance of available amino groups at 60°C was faster than other temperatures and formation of conjugates in this temperature was more successful. A stepwise reduction in free amino group content observed with increasing incubation time. When soy proteins were incubated at pH 8.5 for 8 days at 60 °C, a considerable decrease in available amino group contents occurred. UV absorption results showed similar trend of changes in OPA method. Increasing UV absorption is due to the intermediate Maillard reaction products (MRP). Increasing incubation time, temperature and pH cause a significant increase in UV absorbance. Increasing UV absorption with increasing heating time indicates the fact that Maillard reaction products (MRP) formation is more favorable at alkaline pH. Data of UV absorption are a proper evidence for OPA assay results.
As a conclusion, both OPA assay and UV absorption methods are cost effective, accurate and simple methods which can represent valuable information concerning the Maillard conjugation.

Chickpea (Cicer arietinum L.) seeds are important sources of food proteins. Apart from their nutritional properties, pulse proteins also possess functional properties that play an important role in food formulation and processing. In the present study, the effect of protein extraction pH from kabuli chick pea seeds on solubility, emulsion properties, water absorption capacity and variety nitrogen fractions of isolates were obtained from two extraction methods including alkaline extraction and acidic extraction. In this research, the protein was extracted at pH=2.5 and pH=9.5 and after that the protein was precipitated at Isoelectric point (pH =4.5). All experiments were performed in triplicates and Duncan multiple range test with a confidence interval of 95% was used to compare the means. Protein solubility was studied at pH 2.5 7.0. Environment pH had significant effect on solubility (p≤0.05). The solubility-pH profile of different protein isolates showed minimum solubility in the pH 4.0 and 5.0 and maximum solubility at pH 7 and afterward at pH 2.5, also protein isolates obtained by acidic method (isolate A) had higher solubility than protein isolates obtained by alkaline method (Isolate B). Both two isolates had suitable emulsion properties and water hold capacity. Isolate obtained by acidic method higher emulsification while alkaline method enhanced water absorption capacity (p≤0.05). Electrophoresis of the various fractions revealed that chickpea globulin was made up of sub-units of different molecular weights ranging from 10 to 150 kDa. bands corresponding to molecular weights of 30-40 kDa, which should be attributed to the acidic subunits of the 11S globulin (legumin), while the bands at about 25 kDa probably corresponded to the basic legumin subunit. Bands density of isolate B were thicker, this phenomena could be attributed to nearby of pH utilization for protein extraction at optimum pH of globulin extraction. According to suitable functional properties of chick pea protein isolate, it could be used as a novel protein source substitution in food productions.

Application of optical radiation such as laser and other short wavelength radiation for inactivation of many food-borne pathogen microorganisms in food industry (as major challenges in the food industry and so that many diseases are resulted from this food contamination) was known as a new technology. Effects of green Continuous Waves lasers on structural (using SDS-PAGE method) and physicochemical properties (organoleptic and pH value) of egg Albumen proteins was studied. The results of SDS-PAGE showed that none of the laser radiation treatments, had not changes in structural nor Organoleptic properties (including color and odor quality) of egg white proteins even at the highest time used, Evaluation of the pH values showed no significant difference between control and treated samples in this study. Using of the green continuous-wave laser irradiation method in the food industry can be considered as a new sanitation method for breaking eggs.

Wheat germ is one of main part of wheat kernel that contains relatively high protein content. These proteins cause desired functional properties. Among the functional properties of proteins, solubility is of the most importance, because of its significant influence on the other functional properties. Many factors affect the protein solubility. Two of the most important factors are pH and NaCl concentration. In the alkaline extraction method, maximum solubility of proteins is important and affects the extraction efficiency. An integrate study was conducted on the effects of salt concentration and pH on the solubility of defatted wheat germ proteins. The solubility profile of defatted wheat germ protein also determined as affected by pH 1-12. The solubility at acidic pH values decreased towards the pH value of 4, that is the isoelectric point and then increased for basic pH values, and then solubility reached to maximum level at pH 10. The solubility was determined experimentally in the 0, 0.1, 0.25, 0.5, 0.75 and 1 M NaCl solutions and pH 9, 9.5, 10, 10.5, in order to obtain optimum pH and salt concentration for protein extraction. The results showed that, both salt concentration and pH influenced in the protein solubility, and these properties had great interaction. The protein solubility was higher at pH value of 10 than other pH for all NaCl solutions, however, the maximum solubility was observed at pH 10 in 0.5 M NaCl concentration. The results of the present study indicated that the protein solubility of the defatted wheat germ flour was adversely affected by increasing ionic strength, although the protein solubility in 0.1 to 0.5 M NaCl solutions was similar nearly. The highest protein solubility was observed in 0.5 M NaCl and pH 10. Therefore, it can be concluded that optimum pH and salt concentration for protein extraction from defatted wheat germ are 10 and 0.5 M, respectively. Also, in order to understand the protein subunits distribution profile, and comparison structure of protein isolate from alkaline extraction and defatted wheat germ flour, electrophoresis patterns were determined.