فهرست مطالب مهنوش پارسایی مهر

Despite the beneficial effects of antibiotics in treating livestock diseases and increasing their weight, their residual effects on food can cause harmful effects on both livestock and humans and endanger human health. The presence of antibiotic residues in food, especially meat, and its transfer to the body of consumers is one of their most important harmful effects. One of the practical ways to reduce drug residues in meat is to use heating methods such as cooking in boiling water.

This research aimed to use a suitable cooking method and optimize its conditions in terms of salt content. Organic acids (citric acid) and cooking time to reduce antibiotic residues.

For this purpose, fifteen 20-day-old Ras broiler chickens were used. To clean their bodies from possible antibiotic residues, the chickens were kept for 10 days and given antibiotic-free food. Then, the antibiotic enrofloxacin was injected into the chest muscle, and 24 hours later, they were killed. Based on the protocol provided by Design Expert software, 18 treatments with different cooking time ranges and percentages of salt and citric acid were designed and implemented, and the drug residue after cooking the samples was determined by HPLC (high-performance liquid chromatography) method.

Based on the obtained results, proper cooking methods and optimization of its conditions, such as the amount of salt, organic acids (citric acid), and cooking time, had a significant effect on the reduction of enrofloxacin antibiotic residues. Also, after optimizing the process by the software, the best conditions to achieve the minimum amount of antibiotics could be achieved by the cooking time of 26.59 minutes, 2.95% w/v salt, and 1.49% v/v citric acid.

By cooking properly and adding ingredients such as acids and salt at the optimum level, the amount of antibiotics in chicken meat can be reduced.

Todays, plants have attracted the attention of researchers as natural resources that have antioxidant and antibacterial properties. Spinach plant is widely used in various pharmaceutical and food industries. In this research, the effect of different solvents on the amount of phenolic compounds, antioxidant activity and antibacterial properties of various aqueous, alcoholic (ethanolic, methanolic) and hydroalcoholic extracts of spinach plant has been studied. According to the results obtained from the chemical tests, it was found that by changing the type of solvent from polar to non-polar, the extraction rate of phenolic compounds and therefore the antioxidant activity increased significantly (p<0.05).So that the ethanolic extract with the most non-polar property has 98.5 mg/100 grams of gallic acid of phenolic compounds, while the aqueous extract has 50.7 and naturally the same difference in the amount of phenolic compounds, the amount of antioxidant property for the ethanol extract is135±5 micrograms/ml. if it is 2011 ±12micrograms per milliliter for aqueous extract. According to the results, the MIC for the ethanolic extract was 11479 ppm on gram-positive bacteria and 12467 ppm for gram-negative bacteria, and for the aqueous extract, the MIC on gram-positive bacteria was 52380 ppm and for gram-negative bacteria was 64298 ppm.Therefore, in the case of microbial tests, the effect of non-polar extracts was more than that of polar extracts, which confirms that the type of solvent used has a significant effect on the antibacterial properties of different extracts. (p<0.05) In general, according to the results of this research, non-polar solvents cause the extraction of more phenolic compounds, and considering the antioxidant and antibacterial effects of these compounds, alcoholic extracts will have more antioxidant and antibacterial ability.

Nowadays, the interest in functional food has dramatically increased. Herbal plants and functional foods have health-enhancing effects on consumers due to their medicinal, antioxidant, and nutritional properties. Probiotics are one of the most emerging and popular functional food products. 

This study aims to assess the effect of irradiated and non-irradiated saffron petal extract on the viability of Lacticaseibacillus paracasei (M4PM99) in probiotic yogurt.

The ethanolic extract of irradiated saffron petals with a 10 KGy dose of gamma ray at concentrations of 25, 50, and 75 mg/mL and non-irradiated extract at the same concentrations were used and their effect on the viability of Lacticaseibacilus paracasei and their antioxidant and physicochemical properties in set yogurt were studied. Probiotic survival, pH, acidity, content of total phenolic compounds, DPPH inhibition percentage, and sensory properties on days 0, 7, 14, and 21 were assessed.

Both irradiated and non-irradiated saffron extracts significantly increased the viability of probiotic bacteria compared to the control sample (P<0.05). The addition of extracts was effective in increasing acidity and decreasing pH compared to the control (P<0.05). With the increase in the amount of extract, the percentage of DPPH inhibition and phenolic compounds significantly increased in the irradiated samples (P<0.05). The effect of storage time was also significant on these indicators, such that the antioxidant properties and phenolic compounds increased until the 14th day and then decreased (P<0.05). In the sensory evaluation, in terms of taste, odor, and color, the lowest score was related to the sample containing 0.75% extract. No significant difference was observed in other concentrations compared to the control sample.

Saffron petal extract has a positive effect on the viability of probiotics during storage. Gamma irradiation has a significant effect on the amount of total phenolic compounds and the antioxidant activity of saffron petal extract. It can be used as a natural antioxidant in dairy products.

Digestive system of ruminants is adapted for digesting diets that mainly consist of fodder. Feeding diets with high amounts of grain materials to ruminants causes gastric acidosis and liver abscesses. The aim of the present study was to identify bacterial agents isolated from liver abscesses and to investigate its prevalence in slaughtered cows in Semnan abattoir. In this study, a total of 200 cows were sampled. Rumen acidity was measured immediately after slaughter with a portable pH meter. During the inspection of the carcass, the liver of the cows was examined, and if there was an abscess, the related information was recorded. Then the abscess was completely separated from the liver along with a part of healthy tissue and transferred to the laboratory with ice. In the laboratory, culture of liver abscesses was performed according to the standard method. Out of 200 cattle, 63 (32.5%) had subacute acidosis, of which 40 (31.4%) were males and 23 (31.5%) were females. A total of 12 cattle (6.5%) were suffering from liver abscess. Fusobacterium necrophorum was isolated from 9 (69.2%) abscessed livers and Troperella pyogenes from 6 (46.1%) abscessed livers as the most common cause of abscess. The prevalence of subacute acidosis and liver abscesses in cows slaughtered in Semnan abattoir is 32.5% and 6.5%, respectively. Fusobacterium necrophorum and Troperella pyogenes are the most important causes of liver abscesses in cattle.

Over the past few decades, there has been a surge in interest in the isolation of novel Lactobacillus probiotic strains that exert beneficial effects in the host gastrointestinal tract (GI). probiotics are ‘‘living micro-organisms, which upon ingestion in certain numbers, exert health benefits beyond inherent basic nutrition’’. Most probiotic microorganisms are lactic acid bacteria (LAB), among them lactobacilli represent one of the major microbial groups. They have been introduced in a wide range of food products, including yogurts, cheese and other dairy products as well as non-dairy products, such as fruit juices and fermented sausages. (Bao et al., 2010). In order for a probiotic strain to exert its beneficial effect on the host, it has to be able to survive passage through the host’s digestive tract. So far, research has mainly focused on strains’sensitivity towards low pH, proteolytic enzymes and bile salts. It is considered that the ability of Lactobacillus strains to adhere to the mucosal surfaces of the intestine before they can exert their beneficial effects has long been one of the most commonly encountered criteria for the selection of probiotic strains (Gao et al., 2013). Auto aggregation ability and surface hydrophobicity of bacteria are two independent traits, and their determination has been proposed as an indirect method for evaluating the adhesion ability of bacteria. Also the ability to co aggregate with other bacteria such as pathogens may form a barrier that prevents colonization by pathogenic microorganisms (Collado et al., 2007). The objective of this study was to evaluate the in vitro probiotic potential of the Lactobacillus strain isolated from Semnan traditional cheese (Khiki), and could therefore be potentially used as novel probiotic strain in the food industry.

In this study, the probiotic potential of Lactobacillus paracasei OK561873 isolated from Semnan traditional cheese in previous study by the Department of Food Hygiene, Faculty of Veterinary Medicine, Semnan University was investigated. The isolated bacterium was sequenced based on the 16s rRNA genome and was confirmed as Lactobacillus paracasei confirmed in the BLAST database and registered as a new strain in the NCBI gene bank with code OK561873.Then, to evaluate the resistance of the Lactobacillus isolates to pH ,10 μl of the 24-hour culture of isolate (108 CFU / ml) was mixed with 240 μl of MRS broth at pH adjustments (1.5 and 2.5) in a microwell plate and incubated for 37 h at 37 ° C. Serial dilutions were prepared at 0 and 3 hours and cultured by surface plate in MRS agar medium and incubated for 24 to 48 hours in aerobic conditions at 37 ° C. Finally, the survival percentage of the strain was calculated by bacterial counting. The ability of the strain to grow under acidic conditions in MRS broth at three different pHs 2.5, 3.5 and 4.5 (based on screening experiments) was evaluated, and the growth curve according to the OD values obtained at 630 nm was drawn by ELISA reader (Biotech, USA) during 24 hours. MRS broth containing 0.3, 0.5 and 1% oxgall was used to determine resistance and growth in the presence of bile. The growth curve was drawn using OD630 nm reading in 24 hours by ELISA reader (Biotech, USA). The 24-hour cultured bacterial pellet (108 CFU / ml) was separated by centrifugation (g6000) and washed twice with PBS buffer; then they were suspended in PBS solutions with a pH of 2 and containing pepsin (3 mg/ml) and NaCl (0.5%). After incubation at 37 ° C, live colonies were counted by culture in MRS agar at 0, 60, 90 and 180 minutes. After 3 hours, 1 ml of the previous stage culture was added to 9 ml of intestinal juice containing 1 mg/ml of pancreatic and bile of 0.3% at pH eight, and live bacteria were counted at 0, 2 and 4 hours. To evaluate the antibacterial activity of the isolate, two bacteria, Staphylococcus aureus ATCC 29213 (as an indicator of gram-positive bacteria) and Escherichia coli ATCC 35218 (as an indicator of gram-negative bacteria) were used. The experiment was performed by two methods of spot agar and well diffusion. The hydrophobicity test, is evaluated by measuring the microbial adhesion to hydrocarbons. Auto-aggregation property of probiotic strain can affect the binding capacity of bacterial cells to intestinal epithelial cells, and co-aggregation with pathogens can prevent the colonization of pathogens in the intestine. In brief, four milliliters of the 24-hour culture containing 108 CFU / ml of bacteria were vortexed and homogenized for 10 seconds and then incubated for 5 hours at room temperature. At one-hour intervals, one-tenth of a ml suspension was removed and placed in a new tube containing 3.9 ml of PBS was transferred. Then the absorption of 600 nm was measured using a spectrophotometer.

the viability was evaluated at pH 1.5 and 2.5 on isolated Lactobacillus. No growth was observed at pH 1.5. While at pH 2.5, the number of viable cells was reported to be 6.23 log cfu / ml and showed a good survival rate (75.5%). According to the growth results of Lactobacillus isolate at different pH (2.5, 3.5, 4.5) showed that the growth rate, after the control group, at pH = 4.5 was higher than other groups (P <0.05) But there was no significant difference in other pHs. Lactobacillus paracasei showed good resistance and growth at different concentrations of bile. Growth retardation time of few than 30 minutes was observed, indicating that the isolates were resistant to different concentrations of bile. No significant differences were observed between treatment groups. The results of isolate resistance in the simulated conditions of gastric and intestinal juice showed that at pH 2 and after three hours, the strain survived and only a reduction equivalent to one and a half logarithms was observed. no decrease happened in the intestinal environment, even an increasing growth of strain was observed. The results of the antagonistic effect of Lactobacillus isolate with Staphylococcus aureus and Escherichia coli by spot and well diffusion methods showed that the growth inhibitory effect against the studied pathogens was related to Lactobacillus paracasei with a growth inhibition zone diameter of 2.94±1.39 mm against Staphylococcus aureus and 2.59±1.37 mm against Escherichia coli. There was also no significant difference in the antagonistic effect of lactobacilli isolate against gram-positive and gram-negative bacteria. According to the results, Lactobacillus paracasei isolate showed a high percentage of auto aggregation characteristics and the average percentage during five hours of incubation at 37 ° C was 92.45%. Co-aggregation of Lactobacillus strain with pathogens (Staphylococcus aureus and Salmonella typhimurium) was also investigated. The results are expressed as a percentage reduction after four hours in the adsorption of the mixed suspension compared to the individual suspension and according to the results, the tested strain showed a significant coaggregation with Salmonella typhimurium. Also, the results of hydrophobicity of Lactobacillus paracasei isolate show that this strain can have good hydrophobicity (57. 82%).

The strain isolated from traditional Semnan cheese showed desirable probiotic properties in vitro. Therefore, it is suggested that this isolate, as a new probiotic strain in the food industry, could be a good candidate for further in vitro complementary tests and in vivo research to demonstrate potential health benefits.

Cheese is one of the most important dairy products which contains almost all essential amino acids. Cheese ingredients and environmental conditions often cause excessive growth of fungi and bacteria on the its surface. Therefore, coating and packaging can be considered as a basic step to increase preservation and shelf life. In this study, effect of coating lactic cheese by aloe vera gel, gum arabic and liquid smoke essence on the chemical changes during 21 days of storage in the refrigerator was investigated. Based on the limits determined by Design Expert software, 18 solutions containing 0, 10, and 20% v/v of aloe vera gel, 0, 5, and 10% w/v of gum arabic, and 0, 0.5, and 1% v/v of liquid smoke essential oil was prepared and cheese pieces were coated by immersion method. According to the obtained results, a trend of increasing pH and decreasing acidity was observed in the samples which were coated by maximum amounts of biopolymers and essential oil (20% v/v of aloe vera gel, 10% w/v of gum arabic and 1% v/v of liquid smoke essence). In case of moisture content and weight loss, the best coating solution contained the highest amounts of aloe vera gel and gum arabic, (20% v/v and 10% w/v), respectively. Finally, by optimizing the process by software, the best coating mixture could be produced by 1% v/v of liquid smoke essential oil, 18/507% v/v aloe vera gel and 10% w/v of gum arabic.

Milk is a complete food for all ages and contains nutrients with compounds with different biological activities, and among other food items, it contains high antioxidant capacity in the form of enzymes, proteins, and vitamins. Considering that determining the antioxidant properties of raw milk after industrial and home heat treatments is always one of the most important questions of consumers, this study was conducted with the aim of determining and comparing the antioxidant properties of milk after industrial heat treatments and home heat treatments.

To do this research three diferent commercial brands were used,and from each brand, 10 samples of pasteurized milk and 10 samples of sterilized milk in different batch numbers, as well as 30 samples of traditional and raw milk from dairy stores before and after boiling thermal process were collected randomly and their antioxidant activity were investigated by antiradical(DPPH) test, reducing power test and Total phenolic capacity and their antioxidant power were compared by one-way ANNOVA and Tukey test.

The results showed that in all antioxidative parameters, raw milks that were not subjected to any heat treatment.had the highest values (p < 0.001), followed by pasteurized milk and sterilized milk, and boiled milk had the lowest antioxidant activity (p < 0.001).

In general, the results of this research showed that thermal treatments have a negative and decreasing effect on the antioxidant properties of milk, but since in order to make milk healthy, it is necessary to apply heat treatments,

Shiga toxin-producing Escherichia coli (STEC) strains are one of the main causes of food poisoning and diseases such as hemorrhagic colitis and hemolytic uremic syndrome.  Food contamination mainly occurs through food of animal origin such as meat and dairy products. The aim of this study was to investigate prevalence and distribution of virulence genes in Escherichia coli isolates from traditional cheese from Semnan city, using multiplex PCR method.

In this study, a total of 100 traditional cheese samples were screened for E. coli strains through conventional microbiological tests. Then, screening for virulence genes (Stx1, Stx2, eaeA and hlyA genes) was carried out by using PCR method.

Fifty-nine Escherichia coli strains were identified among 100 cheese samples. Of these, 55 isolates exhibited for one or more virulence genes (93.2%) which, 44 isolates carrying more than of one gene and 11 isolates were positive for the carrier of one gene. Stx2 showed the highest frequency of virulence gene in E. coli isolates.

Therefore, due to the high prevalence of virulence genes in pathogenic E. coli isolates in traditional cheese, it is necessary to use molecular methods to control the microbial quality of these products.

This study aimed to investigate the effect of probiotic Lactobacillus plantarum isolated from traditional Semnan cheese on serum total oxidant and antioxidant status, oxidative stress index and some biochemical parameters in streptozotocin-induced diabetic rats.  Twenty-four male Wistar rats were randomly divided into four groups (six rats in each group) including; negative control, positive control (diabetic control), probiotic control and diabetic rats received Lactobacillus plantarum suspension at a dose of 108 CFU / ml by gavage. Lactobacillus plantarum bacteria identification was performed by mMRS culture and isolation of single colonies and the use of specific biochemical tests and molecular identification of lactobacilli based on the amplification of 16s rRNA gen using polymerase chain reaction (PCR). Hyperglycemia was induced in 12 male rats by intraperitoneal injection of streptozotocin (65mg/kg) (diabetic untreated, and diabetic-probiotic groups). The healthy and diabetic rats treated by probiotic in groups 3 and 4 received probiotic on the 6th day of the study (five days after STZ injection). Fasting blood sugar (FBS) was monitored on days 0 (primary blood glucose), 6 and 21 of the experiment, and serum lipid profile and total oxidant, and antioxidant parameters and oxidative stress index of the rats were measured at the end of the experiment. The results of this study showed that Lactobacillus plantarum suspension at a dose of 108 CFU / ml doses in treated diabetic rats significantly decreased (p < 0.05) fasting blood glucose, triglyceride, total oxidant parameter and the oxidative stress index compared to the control group. For the first, the results of this study indicated that probiotic lactobacillus plantarum isolated from Semnan traditional cheese had the potential to reduce hyperglycemia, dyslipidemia and oxidative stress in streptozotocin-induced diabetic rats.