فهرست مطالب mohammad reza edalatian

One of the most important factors in producing yogurt is choosing the right starter. Native isolates of any country are among the genetic resources of that country, which play a major role in the production and development of the organoleptic properties of fermented products. Therefore, it seems necessary to study the industrial applications of native isolates. In this study, the production of yogurt was investigated by using native starter isolates from traditional Khorasan yogurts and its comparison with yogurts produced with two types of commercial starters.  

Six strains of Streptococcus thermophilus and three strains of Lactobacillus delbrueckii subsp. Bulgaricus isolated from traditional Khorasan yogurts were selected. The proteolytic activity of Streptococcus thermophilus strains was determined according to the method of Erkus et al(2012) and the proteolytic activity of Lactobacillus delbrueckii subsp. Bulgaricus was determined according to the method of Nespolo et al.(2010). Milk acidification activity byall examined strains was evaluated according to the method of Erkus et al.(2012). The production property of gamma-aminobutyric acid of native isolates was also evaluated using the method of Lacroix et al. (2013). Yogurt was produced using commercial starters and native isolates. Acidity and pH were measured according to Iranian National Standard No. 2852. Synersis of yogurt samples was measured using centrifugation according to Çelik (2007) method. In order to measure textural properties, a combination of backward extrusion techniques and Texture Profile Analysis (TPA) was used (Yang et al, 2010). Sensory characteristics of yogurt samples were evaluated by 20 panelists using five-point hedonic scale. This study was conducted based on factorial experiment using a completely randomized design. Statistical analysis of data was performed using Minitab Statistical Software (version 17) and ANOVA. Comparison of means was performed using Tukey’s test at the significant level (p < 0.05).  

The results of proteolytic activity of Lactobacillus delbrueckii subsp. Bulgaricus showed that the L3 code was weaker than the other two strains. All Streptococcus thermophilus strains were positive protease. All Streptococcus thermophilus strains of the study decreased the pH of the milk to 4.6 in less than five hours, and Streptococcus thermophilus strain S6 code, as the fastest acid producer, decreased the pH of the milk to 4.6within 3 and half hours (Figure 2). The results of GABA production showed that among the streptococcus thermophilus strains, S1, S5 and S6 codes had distinct blue discoloration. Among the Lactobacillus strains, except the L3 strain, two other strains produced green color. Of the 18 samples of the yoghurt, S5L2 and S2L2 samples showed the highest decrease in pH and increased in acidity compared to other samples after being stored refrigerated overnight (P <0.05). The other samples had the same pH and acidity changes as the control samples after overnight refrigeration. The results show the ability of yogurt producion by native starters to compete with those produced by commercial starters in terms of technological characteristics. Thus, samples with codes S2L2, S3L1, S3L2, and S1L1 showed less Synersis of   yogurt than commercial starters. This decrease in the Synersis of yogurt might due to the possibility of exopolysaccharide production by these strains. Textural characteristics of yogurt samples were the hardness of the samples in the range of 3 to 4 N, which was significantly different (P <0.05). The lowest hardness was observed for the S3L3, which can be attributed to the poor proteolytic activity of the strain. L3, S6L2, S3L2 and S2L2 had the highest   hardness compared to other compounds and control samples (P <0.05). This differences in the hardness of the samples can be attributed to the possible production of some metabolites by the strains. There was no statistically significant difference in the adhesion properties of the samples (p <0.05). Considering the sensory evaluation scores, it was found that in all respects, S3L3 had the lowest score among the other samples (P <0.05). This was in good correlation with the results of the textural properties of the test. Therefore, this compound was eliminated compared to the control samples. Finally, considering the proteolytic behavior of the strains and the ability to produce acid and GABA, as well as the sensory, rheological and physicochemical properties of 18 samples in comparison to the two control samples, Streptococcus thermophilus strains with codes S4, S2, S5, S1, S6, and Lactobacillus delbrueckii subsp. Bulgaricus strains with codes L1 and L2 have the potential to be used as commercial starters in the form of compounds S1L1, S2L2, S5L1, S6L2, S4L2.

Carrot products such as carrot juice and fermented carrot products possess high nutritional value and they are considered as a major source of β-carotene. Carotenoids because of containing conjugated double bonds, have antioxidant properties and provide the natural yellow, orange and red colors in fruits and vegetables. Due to the outbreak of some problems such as lactose-intolerance and high blood cholesterol especially in dairy products’ consumption, great attention has been drawn toward fermented vegetable products. Lactic acid bacteria (LAB) including important genera: leuconostocs, lactobacilli, streptococci and pediococci are wide-spread and have been divided according to morphological features and fermentation pathway, which utilize glucose. Current knowledge regarding involved microorganisms in vegetable fermentation is still dependent on biochemical and classical data. Nowadays, application of molecular methods in the field of microbial identification has been provided better understanding from fermented foods ecology. Since local starter cultures are considered as precious genetic resources in each country and also they play an important role in production and creation of organoleptic characteristics in fermented products, therefore, the objective of present study was the isolation and identification of lactic flora from fermented carrot with the help of conventional (biochemical) and molecular methods and determination of phylogenetic relationships. Following the production of fermented carrot samples, they were packed in plastic container and stored at ambient temperatures (25-27°C). In the next step, total LAB count was performed according to Iranian standard of 5484. Isolation and selection of LAB was done during 32 days with the intervals of 0, 4, 8, 16, 24 and 32. For initial identification of LAB, isolated were subjected to gram staining and catalase tests. Also biochemical tests including growth at 15 and 45C, at NaCl 6.5% and 18%, pH=4.4 and 9.6, were done in order to identify   and classify at genus level. Carbohydrate fermentation profiles were obtained for isolates with the aid of 10 sugars. Molecular identification was done with DNA extraction followed by amplification of 16S gene with universal primers (27 F and 1492 R). For sequencing of resulted PCR-products, they were sent to Macrogen Company, South Korea. Phylogenetic tree was plotted with Clustal Omega and Fig. Tree soft wares. In the first step, 144 gram positive, catalase negative isolates were screened and selected as presumptive LAB according to gram staining and catalase test and morphological characteristics. Among them, 48 representative isolates were chosen and identified up to genus level according to biochemical tests. Five distinct genera were identified as Pediococci (4.08%), homofermentative lactobacilli (34.69%), hetero fermentative lactobacilli (36.74%), Leuoconostocs (20.41%) and enterococci (4.08%). Carbohydrate fermentation profiles revealed Lactobacilli constitute the highest percent among other genera and also some species like Lb. kimchi and Lb. parakefiri were detected. Growth of lactic acid bacteria experienced increasing trend up to day-16 but thereafter showed decline trend until the end of storage time (day-32). 26 out of 48 isolates were subjected to molecular analysis. Results of sequencing revealed following species: Lb.plantarum (9), Lb. brevis (8), Leu. mesenteroides (4), Lb. casei (1), Lb. paracasei (1), and Lb, pantheris (1). Changes and variation of lactic flora during fermentation stages revealed that at initial stages of fermentation  (0- day-8) Leuconostocs sp. were predominant species but disappeared then. In the next stages of fermentation Leuconostocs sp. were replaced by homo-fermentative strains such as Lb. plantarum which was present from the first day up to day-24 but constituted the majority of species on day-16. In the final stage, Lb. brevis dominated the others due to better survival and resistance of this bacterium at the increased acidity level. Phylogenetic tree results revealed three clusters including cluster I (composed of three sub-clusters), cluster II (three sub-clusters) and cluster III (two sub-clusters). Cluster I included two genera: Leuconostocs sp. (mesenteroides) and Lactobacillus (pantheris, casei and paracasei). Cluster II included Lb. brevis and finally cluster III composed of Lb. plantarum.

In this study, the effect of different inoculum concentrations of E. faecium subsp. faecium strains on chemical, microbial and sensory properties of doogh was evaluated during two months of storage at 4 and 25°C. As compared with the control samples, samples containingstrain 1 of E. faecium subsp. faeciumand strain 2 of E. faeciumsubsp. faeciumat concentrations of 106 and 108 cfu/ml showed that decreasing of pH and increasing of acidity in the first month of storage.Also, inoculated samples of doogh with E. faecium subsp. faecium strains showed a significant decrease (p˂0.05) in the enumeration of molds and yeasts, coliform and mesophilic microorganisms at both storage temperatures (4 and 25°C). Among the samples, inoculated doogh sample with strains of E. faecium subsp. faecium with concentration of 108 cfu/ml was more effective in reducing the unwanted microbial load. Samples of inoculated doogh with concentration of 108 cfu/ml at 4 °C had an acceptable shelf life up to 50 days, while it was 40 days for the same control sample counterpart. Sensory evaluation showed that inoculated doogh samples were more acceptable than control doogh samples stored at 4°C. Generally, the E. faecium subsp. faecium strains, due to more decreasing of pH and higher acidification, reduced microbial load, and have a positive effect on sensory properties then can be used as a co-culture in the production of fermentation dairy products.

In this research, the chemical and microbiological characteristics of white brined cheeses produced with five different starter cultures, namely: traditional kefir grain, commercial kefir, commercial yogurt, traditional yogurt and commercial cheese starter culture, were examined during 60-day ripening period. Results of statistical analysis showed that the type of starter culture had a significant effect on pH, acidity, fat, protein, moisture, enterobacteria, total counts, mold and yeast as well as on lactococcus (p < 0.01), and lactobacillus level (p < 0.05). pH, acidity, fat, protein, total count, mold and yeast, and lactobacillus level (p < 0.01) were significantly affected by starter culture type during ripening period. However, moisture, enterobacteria and lactococcus level in all cheese samples were not affected by ripening period. Whereas other parameters including pH, fat and protein content showed decreasing trend during ripening. Among chemical analyses, cheese produced with traditional kefir had highest pH and cheese produced using commercial kefir showed highest acidity and moisture. Among microbial parameters cheese produced with commercial kefir starter had the lowest total microbial count and after that cheese using traditional kefir starter. It is concluded that traditional kefir grain can be used as a starter culture in production of functional white brined cheese.

In this study, Molecular method to measure the rhizopus oryzae Real Time PCR was used in tomato paste. Because of problems mold count HMC method such as Proofer error, low and non-repeatability precision, accuracy and repeatability developing a standard method that can enable high accuracy and repeatability and mold counts it seems necessary. Real Time PCR molecular methods can be used as a suitable method to identify and quantify the precise mold is considered that based on the measurement of absolute and relative genes is the existing molds. Tomato paste samples with different amounts of mold spores (101, 103 and 105) were contaminated per gram. After incubation and growth of mold spores and mycelium extraction DNA from each sample was performed using al-sammari method. Then, using Real Time PCR reaction of DNA copy number of molds using SYBR Green reagent and primers of the rhizopus oryzae genus was determined. The results showed that increasing amount of DNA molds in controls and inoculated samples resulted Real Time curve in the lower CT values are entered logarithmic phase. The correlation coefficient of linear calibration Real Time was R2 = 0/943. This indicate that the accuracy of this test is quantitative detection. The reaction specificity was determined using melting curve of the primers and indicated that the reaction has been completely dedicated.

In this research different methods of DNA extraction from Aspergillus niger in tomato paste have been optimized and compared with each other. For this purpose classical optimization techniques and commercial Kit base methods were used. Mold spores of Aspergillus niger at different levels (101, 103 and 105 CFU/g) were added to the tomato paste. After mycelium growth DNA extraction was perfomed by five methods. Different methods employed by use the Liquid nitrogen, ultrasonic and lysis solution in the cell wall. These methods in terms of quality and quantity of DNA extracted were studied using spectrophotometer with NanoDrop. The absence of smear, protein contamination and no presecnce of PCR inhibitors determined with PCR that performed forward and reverse primers. Result of gel electrophoresis and PCR assay showed that Method 1 is the most appropriate method for DNA extraction is the mold of tomato paste.

Studies have shown that camel milk and its fermented products have therapeutic properties and high nutritional value. Lactic acid bacteria play important role in Fermented dairy products. The aim of this study is to determine the lactobacillus community of camel milk. A total of 9 Lactobacillus were isolated from camel milk of Golestan province in Iran. The log10 CFU of Lactobacillus per ml on MRS medium under anaerobic condition at 20, 37 and 450C included 8.792± 0.14, 8.301±0.07 and 7.301±0.03 respectively. Isolates were identified on the basis of Biochemical and Phenotypic Characteristics as Lactobacillus paraplantarum, Lactobacillus ferintoshensis, Lactobacillus brevis, Lactobacillus pantheris, Lactobacillus johnsonii, Lactobacillus mali. Presence of Lactic acid bacteria was confirmed by band formation of PCR product in 1500 bp (amplification 16S rRNA gene using B27F-U1492Runiversal bacterial primer). Evaluation of their technological properties of isolates showed that isolated Lactobacillus fromcamelmilkhave lipoliticy, Proteolytic activity and high acidifying activity (except for Lb. mali and Lb. johnsonii). Also, allisolates, except Lb. Johnsonii, have autolytic activity in fair level. Based on technological properties ofisolates, Lb. paraplantarum, Lb. Brevis and Lb. pantheris are suggested as good candidates for camels milk processing or other fermentation process.

With emerging of infectious diseases and spread of antibiotic resistant strains, use of antimicrobial compounds with plant origin seems necessary. In this study, ethanolic extract of Cordia myxa fruit was used to evaluate antimicrobial effects against microorganisms including Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhi, Aspergillus niger and Candida albicans. Ultrasound-assisted extraction was performed to investigate three independent variables: time (5- 40 min), temperature (20- 50°C) and sonic power (20- 100%). Response surface methodology was also employed to optimize multiple variables to predict the best process conditions. Antimicrobial activity was done by methods including disk diffusion agar, pour-plate, minimum inhibition concentration and minimum bactericide (fungicide) concentration. The results showed that the highest amount of extraction rate of ethanolic extract which was equal to 8.5%, was obtained in extraction time of 39.8 min, temperature of 42.2°C and sonic power of 94.4%.In all above-mentioned methods, inhibitory effect of optimum ethanolic extract was more significant againstBacillus cereus, Staphylococcus aureus and Candida albicansthan other strains (p≤0.05).

In this study, molecular method used to measure the Aspergillus niger with Real Time PCR technique in tomato paste. Because of problems mold count method such as proofer error, low and non-repeatability precision, accuracy and repeatability, developing a standard method high accuracy and repeatability and mold counts seems necessary. Real Time PCR molecular method can be used as a suitable method to identify and quantify the precise mold is considered based on the measurement of absolute and relative genes existing molds. Tomato paste samples with different amounts of mold spores (101, 103 and 105) per gram were contaminated. After incubation and growth of spores and mycelium of mold, DNA extraction from each sample was performed using al-sammari method. Then, using Real Time PCR reaction of DNA copy number of molds using SYBR Green reagent and primers of the Aspergillus niger genus was determined. The results showed thatby increasing amount of DNA molds in controls and inoculated samples Real Time curve were entered logarithmic phase in the lower CT values. The correlation coefficient of linear calibration Real Time was R2 = 0/938 which indicates that the accuracy of this test is quantitative detection. The reaction specificity was determined using melting curve of the primers and indicated that the reaction has been completely dedicated.

One of the pathogenic bacteria species in the genus of Lactococcus is Lactococcus garvieae. It causes human disease (endocarditis) and mastitis in dairy cows to appear. The presence of these bacteria in the raw milk products like Lighvan cheese was reported. Lighvan cheese is a traditional cheese which is made from raw sheep's milk.In this study, fresh milk, curd, Fresh cheese and ripe cheese, and fresh grass Lighvan area was used to isolate bacteria. Biochemical tests at 10°C and 45°C and grow in salt concentration 4% and 6.5 %, was performed. After extraction of DNA, PCR reaction with primers for genes of Lactococcus 16S rRNA performed and the products were sequenced by the company Source BioScience England, then in gene databases NCBI, the sequence of which more than 97% were similar in terms of genus and species were identified.At first, 1500 colonies similar to Lactococcal genera isolated from different sources such as fresh grass, fresh milk, curd, fresh cheese and ripened cheese according to colony morphology. Then, the 625 isolates were selected by gram stain. The biochemical tests carried out to select 60 isolates of Lactococcal genus and the PCR was used to determine the 16S rRNA gene sequence region to identify species. Based on molecular identification 50 species, were belonged to the Lactococcal genera and finally two species of Lactococcus were Lactococcus garvieae.According to the results, the presence of two species of Lactococcus garvieae (fresh milk and curd) was demonstrated in the early stages of Lighvan cheese production, But, there was no presence of the bacteria in fresh cheese and ripened cheese.

Camel milk is amongst valuable food sources in Iran. On the other hand, due to the presence of probiotic bacteria and bacteriocin producers in camel milk, probiotic bacteria can be isolated and identified from this food product.. The objectives of the present research were the isolation and molecular identification of lactic acid bacteria from camel milk and evaluation of their probiotic properties.. A total of ten samples of camel milk were collected from the Golestan province of Iran under aseptic conditions. Bacteria were isolated by culturing the samples on selective medium. Isolates were identified by amplification of the 16S rDNA and Internal Transcribed Spacer (ITS) region between the 16S and 23S rRNA genes by Polymerase Chain Reaction (PCR) and were then screened and grouped by the Amplified Ribosomal DNA Restriction Analysis (ARDRA) method. To evaluate probiotic properties, representative isolates of different ARDRA profiles were analyzed. The antimicrobial activity of Lactic Acid Bacteria (LAB) against Pediococcus pentosaceus, Escherichia coli and Bacillus cereus was examined by the agar diffusion assay. Acid and bile tolerance of isolates were evaluated.. A total of 64 isolates were analyzed based on biochemical tests and morphological characteristics. The most frequently isolated LAB was Enterococci. Weissella, Leuconostoc, Lactobacilli and Pediococci were less frequently found. Based on restriction analysis of the ITS, the isolates were grouped into nine different ARDRA patterns that were identified by ribosomal DNA sequencing as P. pentosaceus, Enterococcus faecium strain Y-2, E. faecium strain JZ1-1, E. faecium strain E6, E. durans, E. lactis, Leuconostoc mesenteroides, Lactobacillus casei and Weissella cibaria. The results showed that antimicrobial activity of the tested isolates was remarkable and P. pentosaceus showed the most antibacterial activity. In addition, E. durans, E. lactis, L. casei and P. pentosaceus were selected as probiotic bacteria.. This study revealed the presence of bacteriocin-producing bacteria and probiotic bacteria in camel milk from the Golestan province of Iran..

The objective of this study was to evaluate lactic flora identification in fresh (one-day) and ripened (90-day) Koozeh cheese samples as one of the raw milk cheeses. In first step, in order to isolate the different genera of Lactic acid bacteria (LAB), selective and differential (corresponding) media were used as follow: MRS for lactobacilli and pediococci, MRS+ vancomycin for leuconostocs, M17 for lactococci and KAA for enterococci. Totally, 48 single, purified colonies were selected and identified using confirmatory, biochemical and phenotypic tests down to the genus level. Lactobacilli (33.33%), lactococci (12.5%), pediococci (2.08%), enterococci (47.91%) and aerococci (4.16%) were determined as the most abundant genera. At last, carbohydrate fermentation profile using API 50 CH and API 20 STREP kits was used for identification down to species level. Finally, following species were identified: Lactobacillus. plantarum, Lb. brevis, Lb. lindneri, Lb. helveticus, Lb. delbrueckii ssp. delbrueckii, Lb. pentosus, Lb. fermentum, Lactococcus. lactis ssp. lactis, Enterococcus. faecium, Ent. faecalis, Ent. avium, Ent. durans and Aerococcus. viridans. In fresh cheese, the Lactococci and lactobacilli genera were predominant but in ripened cheese the enterococci replaced them. Predominant species in fresh cheese were as follow: Lac. lactis ssp. lactis (44.44%) and Lb. plantarum (22.22%) but Ent. faecium (43.58%), Lb. brevis (12.82%) and Ent. faecalis (7.69%) constituted the major part in ripened cheese. We can mention that these predominant lactic acid bacteria play an important role during ripening and also flavor production in raw milk cheeses like Koozeh. So, more precise identification is very necessary using culture- based molecular and culture- independent methods down to strain level.