جستجوی مقالات مرتبط با کلیدواژه "پایداری حرارتی" در نشریات گروه "پزشکی"

Due to the unfavorable effects of synthetic antioxidants, the use of various sources of plant antioxidants to retard or prevent oxidation of foods, especially oil-based or fat-based varieties, has today received considerable attention.

Inorder to extract the essential oil, water distillation method was applied and the extract of citron peel was obtained by ultrasound and maceration methods by using ethanol, methanol and water as solvents. Total phenolic compounds of the extracts and their antioxidant activities were measured. The chemical compounds in the extract and essential oil were identified by gas chromatography. Finally, the antioxidant effect on the stability of sunflower oil was investigated. The stability of oil to oxidation during storage for 5 days at 65 ° C was assessed using peroxide, anisidine, thiobarbituric acid, Tutox values and oxidative stability index.

The most amounts of phenolic compounds and antioxidant activity was absorved in ultrasonic-assisted ethanolic extract at 30 min. The extract concentration at 800 ppm was more effective to radical scavenging than the other concentrations. The major compounds of citron peel extract were nomilin and hesperidin. The results showed that the peroxide, anisidine, and totox value had an increasing trend over time. Ultrasonic-assisted ethanolic extract at 30 min showed the highest OSI.

The results of this study demonstrate the beneficial effects of the essential oil and extract from citron peel on sunflower oil stability and its superiority over synthetic antioxidants.

Due to the increasing consumption of fried foods, it is important to check the quality of the oil used for frying to maintain the health of consumers. Therefore, this study aimed to determine the amount of peroxide, acidity, and thermal stability of the oils used in Falafel stores in Arak, Iran.

This cross-sectional study was performed on 25 traditional units and 2 industrial units producing Falafel in Arak, Iran, during 2018. In total, 50 and 3 samples were obtained from traditional (two samples from each unit) and industrial units, respectively, to determine the peroxide and acidity based on the standardized methods No. 4178 and 4179. Moreover, thermal stability was measured using the Rancimat device. The data were analyzed using SPSS  software (version 22) through with Wilcoxon tests and correlated t-test.

The results showed that the peroxide and acidity of the used oils were higher than the allowable limit, and the thermal stability was lower than the allowable limit. According to the obtained data, the samples were rejected in terms of peroxide content of 72%, acidity of 68%, and thermal stability of 98%.

These findings show the inefficiency of the oils used in Falafel stores in Arak, Iran. In addition, the shelf-life of half-cooked Falafel should be reduced.

Aequorin is a calcium sensitive photoprotein composed of apoaequorin (189 amino acid), oxygen and coelenterazine (imidazopyrazine chromophore). Activity of this photoprotein in calcium presence is blue photon emission (469 nm). Studies have shown that three amino acids H16, Y82, W86 are involved in color shift and activity of Aequorin. In this work, for study of structural-functional relationship, combinational mutant was used for determine of the interest places importance in single and combination state. Using site directed mutagenesis, the single and multiple mutations done in plasmid and mutated aequorin in single and multiple states were prepared. Next, thermostability, activity and color shift of produced protein determined using luminometer and spectrofluorimetry, respectively. We found that W86 and H16 play a more critical role in color shift and activity respectively. In addition, mutation of W86 provides better termostability compared to other mutations. This investigation was shown that the role of W86 in aequorin shift light and thermostability is better than Y82 and H16 and this mutant could be used for effective protein production in sensor and other applications.

Fatty acids are one of the most important compounds in edible oils. Further, the stability of oils depends on the composition of fatty acids. So, this study was conducted to investigate the effect of fatty acid composition on the oxidative stability of extra virgin olive oils during the heating process. In total, eight samples of extra virgin olive oil were studied. To evaluate their thermal stability, the oils were heated at 120 ° C for 4 h and sampling was carried out in 2-hour intervals. Then, fatty acid composition, peroxide value, anisidine value and totox value were evaluated according to Iranian national standards. Results showed a significantly direct correlation between Palmitoleic acid and Totox index in the second (r=0.786) and fourth hours (r=0.762), and between linoleic and Totox index in the second (r=0.643) and fourth hours (r=0.786). However, there was a significantly inverse relationship between oleic acid and Totox index in the fourth hour (r=-0.833). Result indicated that linoleic and Palmitoleic acids had a reducing effect on thermal stability of extra virgin olive oil after the second hour. But, Oleic acid caused a positive effect on thermal stability after the fourth hour. Thus, it is concluded that unsaturated fatty acids especially oleic acid affect the thermal stability at final hours.

Fossil fuel is an expensive and finite energy source. Therefore، the use of renewable energy and biofuels production has been taken into consideration. One of the most suitable raw materials for biofuels is cellulosic compounds. Only microorganisms that contain cellulose enzymes can decompose cellulose and fungus of Trichodermareesei is the most important producer of this enzyme. In this study the nucleotide sequence of endoglucanase II، which is the starter of attack to cellulose chains، synthesized from amino acid sequence of this enzyme in fungus T. reesei and based on codon usage in the host; yeast Pichiapastoris. To produce optimized enzyme and to decrease the production time and enzyme price، protein engineering will be used. There are some methods to improve the enzymatic properties like site-directed mutagenesis in which amino-acid replacement occur. In this study two mutations were induced in endoglucanase enzyme gene by PCR in which free syctein positions 169 and 393 were switched to valine and histidine respectively. Then this gene was inserted into the pPinka expression vector and cloned in Escherichia coli. The recombinant plasmids were transferred into P. pastoris competent cells with electroporation، recombinant yeasts were cultured in BMMY medium and induced with methanol. The sequencing of gene proved the induction of the two mutations and the presence of recombinant enzyme was confirmed by dinitrosalicilic acid method and SDS-PAGE. Examination of biochemical properties revealed that the two mutations simultaneously decreased catalytic power، thermal stability and increased the affinity of enzyme and substrate.