Leila Monjazeb Marvdashti; Masoud Yavarmanesh; Arash Koocheki
Abstract
Introduction:Packaging is an important factor in food industry and is dominated by petroleum-derived polymers. Therefore, the amount of research involving the production and characterization of biodegradable films has increased substantially, mainly due to interest in minimizing the ecological impact ...
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Introduction:Packaging is an important factor in food industry and is dominated by petroleum-derived polymers. Therefore, the amount of research involving the production and characterization of biodegradable films has increased substantially, mainly due to interest in minimizing the ecological impact caused by the use of synthetic packaging materials. Several biopolymers have been exploited to develop eco-friendly food packaging materials. Usually, films based on biopolymers are highly sensitive to environmental conditions and generally present low mechanical resistance. As a result, several researchers have developed films based on mixtures of biopolymers and synthetic polymers. In order to increase the workability and flexibility of biodegradable films, various plasticizers, usually poly-ols, have been widely used, glycerol being one of the most preferred and most studied. Plasticizers reduce intermolecular forces, increase the mobility of the biopolymer chains and thereby improve the mechanical properties of the films. Therefore, the aim of the present study were to investigate the effect of different proportions (20e100% w/w) of plasticizer (glycerol) on physicochemical, mechanical, permeability, surface and thermal properties of biodegradable PVA-AHSG blend films.Polymer blending is one of the most effective methods to have new material with desired properties. Films formed by blending of polymers usually results in modified physical and mechanical properties compared to films made of individual components. Since synthetic polymers are easily obtained and have low production cost, blending of natural and synthetic polymers improves the cost performance ratio of the resulting films. Since Alyssum homolocarpumseed gum (AHSG) is environmentally friendly due to its biodegradability and has good film forming properties, it is considered as a very promising biopolymer. Some synthetic polymers from non-renewable sources are also biodegradable, such as polyvinyl alcohol (PVA). PVA is a synthetic, water soluble polymer with excellent film forming, emulsifying, and adhesive properties. It also imparts good tensile strength (TS) and biodegradability and hence has been used in many biomaterial applications. PVA has also been approved for use in packaging meat and poultry products by the USDA (DeMerlis&Schonek, 2003). AHSG contains free hydroxyl and amine groups, and is therefore miscible with PVA due to the formation of hydrogen bonds.Materials and methods: The aim of this study was to investigate the possibility of producing a novel biodegradable blend film from PVA-AHSG with glycerol as plasticizer in the different concentrations. Films were prepared by the casting method using PVA and AHSG (60:40 ratio). Glycerol was used ac plasticizer because it is compatible with PVA-AHSG blend improving film flexibility, facilitating its handling and preventing cracks. The PVA–AHSG blend film was prepared with different glycerol concentration (20–70%, w/w).The optical properties such as opacity and color were measured. Water vapor permeability, moisture content, water solubility and density of the films were also investigated. Films were evaluated for mechanical and antitoxin properties. The PVA–AHSG blend films were characterized using DSC, FTIR and scanning electron microscopy.Results and Discussion: The results of this study showed that blend of PVA and AHSG could be used as a new film-forming material. However, it was not possible to make PVA-AHSG blend films without addition of glycerol as a plasticizer to the formula. Glycerols in 20-70% (w/w) concentration were used to prepare the blend films. At the level of 20% (W/W) of glycerol, PVA-AHSG blend films had the lowest thickness (0.065 mm), moisture sorption (118.76%), water vapor permeability (WVP) values (4.9 g mm m-2 kPa−1 d-1), elongation at break (EB)(2.1%), moisture content (22.5%) and water solubility (16.6%) and the highest values for tensile strength (TS)(64.6 MPa), young modulus (YM) (892 MPa),density (0.109 g cm-3),opacity (0.069 A/mm) and water contact angle (74.52◦). Increasing of glycerol concentration in PVA-AHSG blend films resulted in increase in water vapor permeability and percent of elongation while, decreased tensile strength and surface hydrophobicity. Increasing the glycerol concentration significantly (p < 0.05) diminished initial water contact angle of films from 74.52◦ to 37.80◦. It has been shown that the addition of plasticizers diminished the films’ water contact angle, which in turn, decreased hydrophobicity of the films. The higher hydro-philicity of the samples is attributable to the hygro-scopicity (water-binding capacity) of the plasticizer. Plasticizer can diminish interactions between biopolymer molecules and increase solubility due to its hydrophilic nature, giving the polymer molecules higher affinity to attract water. The moisture content increased significantly from 22.5% to 40.9% as the plasticizer content increased (p < 0.05). Because of glycerol acts as a water-holding agent, with the higher number of water molecules in glycerol-plasticized films increasing plasticizing activity.WVP increases as plasticizer content of the film increases due to its hydrophilic nature. WVP can be directly related to the quantity of OH group on the molecule. Also, environmental conditions can significantly affect the WVP. Increasing plasticizer concentration decreased the intermolecular forces between polymer chains and increased free volume and segmental motions, allowing water molecules to diffuse more easily and giving a higher WVP. Mechanical strength of films decreases due to plasticizer addition resulting in decreased tensile strength and increased elongation. The measurement of color values showed that by the increasing of the glycerol concentration in polymers blend matrix, the b and L values increased while a value decreased. Furthermore, the addition of glycerol promoted the interactions among PVA, AHSG and glycerol through hydrogen bonding as reflected on the shifting of main peaks of the glycerol-free film to higher wavenumbers as shown by FTIR spectra. Microscopic views indicated smooth and uniform surface morphology without obvious cracks, breaks, or openings on the surfaces after the incorporation of glycerol as a plasticizer. Scanning electron microscopy showed that the microstructure of PVA-AHSG blend films have a critical effect on their physical and mechanical properties that is important in food packaging applications.
Mohammad Reza Edalatian Dovom; Masoud Yavarmanesh; Fariba Ghiamati Yazdi; Morteza Khomeiri; Neda Nayyeri
Abstract
Introduction : Lactic acid bacteria (LAB) are a group of gram positive, catalase negative bacteria which possess unique metabolic, physiological and morphological characteristics. In addition, lactic acid bacteria are considered as a valuable source of antimicrobial agents including bacteriocins. Bacteriocins ...
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Introduction : Lactic acid bacteria (LAB) are a group of gram positive, catalase negative bacteria which possess unique metabolic, physiological and morphological characteristics. In addition, lactic acid bacteria are considered as a valuable source of antimicrobial agents including bacteriocins. Bacteriocins are defined as non-toxic peptides produced by LAB. "Maskeh" as an Iranian traditional butter carries indigenous LAB which secrete and harbor bacteriocins. Our objective in this study was to evaluate the influence of antimicrobial compoundsproduced by isolated LAB from Maskeh, a local traditional butter, against some pathogenic bacteria suchas: staphylococcus aureus, Listeria innocoa and E. coli using culture-based methods. In the following step, influence of some technological parameters including different temperatures, pHs and proteinase K were determined on stability of antimicrobial compounds in bacteriocins.Materials and methods: Three samples of milk, yoghurt and local butter known as Maskeh were collected from different regions in the south ofKhorasanRazavi, Gonabadcity.Indicator microorganisms and culture condition: In order to activate the indicators, following the cultivation in corresponding and suitable media, they were incubated for 24 hours in suitable temperatures.Survey of antimicrobial activities: In Agar Spot, Antagonistic activities of isolates were evaluated in solid media. Finally clear zone of inhibition was measured in mm. In Well- Diffusion Assay (WDA), positive isolates from previous step, were selected for this assay. In this method, cell-free supernatant (CFS) of isolates were examined for their antagonistic activities. Finally clear zone of inhibition were evaluated around the wells.Determination of antimicrobial compound nature: Effect of proteinase K on CFS: In order to evaluate the enzyme sensitivity of bacteriocin like compounds produced by LAB, CFS of isolates were subjected to proteinase K (final concentration 0.5 mg/ml). Mixture of enzyme- CFS was incubated in 37C for four hours. Finally, the remaining inhibitory activity was determined using WDA.Influence of different temperatures on CFS: Heat sensitivity of bacteriocin like compounds was evaluated with subjecting the CFS of isolates to various temperatures. Again remaining activity of isolates was evaluated with the help of WDA.Influence of different levels of pH on CFS: CFS of isolates was adjusted at different pHs and their inhibitory effects were determined using WDA.Discussion & Results: Following the sequencing, 51 isolates were identified from different steps of Maskeh production. Results showed that 44 out of 51 isolates were effective at least against one indicator. It was clear that E.coli, Staph.aureus, Listeria. innocoa, Lb.plantarum, Lb.sake, Lac.lactis ssp. lactis,Lac.lactis ssp. cremoris were inhibited by 33, 7,11,12,7,35 and 7 isolates, respectively. Among pathogenic indicator bacteria, E.coli was inhibited maximally and regarding the non-pathogenic indicators, Lac.lactis ssp. Lactis was inhibited by the most of the isolates. Among the isolates, Ent.faecium B161 and Str.thermophilus B258 presented the highest inhibitory effect against Listeria.innocoa.Interestingly both these strains had been isolated from Maskeh, implying that they originated the same source. Formation of clear inhibition zone in agar spot method is related to colony-associated antimicrobial compounds like H2O2, lactic acid and other organic acids. Also, the strongest clear zone of inhibition was against Listeria.innocoa. Lb.plantarum B120 showed inhibitory effect against 6 out of 7 indicator bacteria. This strain has been isolated from Maskeh, and only did not affect on Lac.lactis ssp. lactis.In the next step, in WDA, CFS obtained from isolates were subjected to inhibition activity evaluation. In this assay, 39 isolates showed inhibitory activity against at least one indicator and 12 isolates had no inhibition against indicators. E.coli was inhibited by the most of the isolates (11), followed by Listeria.innocoa by 8 and Staph.aureus by 2 isolates. But noticeable point is that the strongest influence was seen against Listeria. In the last step, influence of technological parameters such as : temperature, pH and enzyme were determined on antimicrobial and inhibitory activity of CFS. In this survey, only those isolates were chosen which showed inhibitory effect against Listeria innocoa. Regarding the temperature, with increasing of this factor, the diameter of clear zone had decreasing trend. This means that bacteriocin- like compounds are sensitive to heat. Among analyzed isolates, CFS of two isolates namely Aerococcusviridans M156 and M141 possess the highest sensitivity. In contrast, the highest resistance was related to Aerococcusviridans M165. Evaluation of antagonistic activity of CFS of isolates at different pHsexperienced, in pH between 3-5, growing trend of inhibitory activity which is due to produced lactic acid. Maximum of antagonistic activity was seen at pH=3 and along with pH increase toward the alkaline condition, it decreased.Aerococcusviridans M165 and M141 showed clear zone of inhibition equal to 6.5 and 6, respectively at pH=7.Proteniase K as a proteolytic enzyme, exhibited decomposing influence on antimicrobial effects of all isolates, except two of them. This phenomenon implies the proteinaceous nature of antimicrobial compound in CFS, because of decomposition as a result of proteolytic enzyme. But regarding two isolates, the clear zone did mot destroyed even after enzyme treatment.Conclusion: Some CFS or their producing isolates can be exploited as bio-preservatives; CFS of Aerococcusviridans M 165 can be applied in foods subjected to high heat treatment. In acidic and low pH food, we can use those isolates which theirCFS remain their activity at low pH.
Nasim Pourebrahim; Masoud Yavarmanesh
Abstract
Introduction:Pistachio nut is one of the popular tree nuts. Among the different species of the genus Pistacia, only the fruits of Pistacia vera attain optimal size to be acceptable to consumers as edible nuts. Contamination of pistachio by Aspergillus species and their mycotoxins is the most important ...
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Introduction:Pistachio nut is one of the popular tree nuts. Among the different species of the genus Pistacia, only the fruits of Pistacia vera attain optimal size to be acceptable to consumers as edible nuts. Contamination of pistachio by Aspergillus species and their mycotoxins is the most important problem for consumption and export of this product. Aflatoxins are potent toxic, carcinogenic and mutagenic secondary metabolites primarily produced by two fungal species, Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus produces AFB1 and AFB2, while Aspergillus parasiticus produces AFB1, AFB2, AFG1 and AFG2. Among four main groups of aflatoxins, AFB1 is the most potent carcinogenic compound. Therefore, identification of toxigenic fungi is necessary for evaluating the foods quality and the presence of mycotoxins. The current methods being used for assessing fungi presence in foods based on cultivation methods and microscopic characteristics are time-consuming and labor-intensive. Recently, molecular techniques such as polymerase chain reaction (PCR) due to high sensitivity, specificity and rapidity has been introduced as powerful tools for detecting toxigenic fungi. Many genes involved in the biosynthesis of these mycotoxins have been identified and their DNA sequences have been published. PCR methods can be used to detect of aflatoxigenic Aspergilli based on structural genes (nor1, ver1 and omtA) encoding key enzymes in aflatoxin biosynthesis pathway and the regulatory gene aflR.
Materials and method: Pistachio samples were collected from different cultivation regions of two towns including Gonabad and Feyzabad. Samples were packed in sterile plastic bags and immediately transferred to the laboratory. The moisture content of samples was determined using thermal method and drying in at 95-100°C. Among fungal isolates 30 Aspergillus genus were detected and purified by cultural-based methods using PDA (potato dextrose agar) medium. Colonies of the fungus were transferred to PDB (potato dextrose broth) medium and incubated for 5 days at 28°C with shaking at 150 rpm. The mycelium was frozen in liquid nitrogen and ground to a powder for later DNA isolation. DNA was extracted with CTAB (cetyl trimethyl ammonium bromide) extraction buffer, then was purified with organic solvents such as chloroform/isoamyl alcohol and finaly was precipitated by isopropanol. Aspergillus genus were detected using polymerase chain reaction by specific primer pair Asp1/Asp2 for amplification of 18S rRNA region. Furthermore, aflatoxigenic genes were detected by three sets of primers (APA-450/APA-1482, ver1/ver2 and OMT-208/OMT-1232). PCR was performed in a volume of 25 µl containing 0.5 µl of each primer, 12.5 µl of Taq DNA polymerase master mix red, 10.5 µl of sterile distilled water and 1 µl of genomic DNA as template. A PCR consisted of an initial denaturing step of 5 min at 94°C followed by 35 cycles (30 s at 94°C, 35 s at 65°C and 40 s at 72°C) finished by a final extension step at 72°C for 10 min. The PCR products were analyzed by electrophoresis on a 1% agarose gel in TBE.
Results and Discussion: Among fungal isolates 30 Aspergillus genus were detected using microscopic characterstics and colony color. Under the microscope, conidia were one-celled, spherical, hyaline or pigmented and they formed long chains. 12 and 4 out of 30 samples had omtA and ver1 genes respectively. No observation was found for aflR regulatory gene in the fungal isolates. The results showed that although some isolates had one or two structural genes in the aflatoxin biosynthetic pathway, they could not produce aflatoxin due to not having any aflR gene. Coefficient of correlation was calculated to find the relationship between the existence of Aspergillus molds and aflatoxigenic genes in pistachio. The statistical results indicated that there is a significant correlation between the enumeration of Aspergillus molds and the existence of genes (omtA and ver1) in different moisture domains (p> 0.05) while no significant correlation was identified between the enumeration of Aspergillus molds and the existence of genes in different domains of enumeration of mesophilic bacteria, yeasts and molds. Contamination of nut seeds by fungi occurs during growth, harvesting, transport and storage. The production of aflatoxin is affected by different factors, such as genetic properties of the producing fungi, temperature, moisture content, the chemical composition of food and antimicrobial agents produced by other microorganisms. Water stress and temperature are the most relevant environmental factors which influence fungal growth and mycotoxin production. Other studies showed that there was a good correlation between the expression of an early structural gene (aflD) and aflatoxin B1 production in peanut seeds. Also previous studies have shown that there was a significant relationship between A.flavus contamination in the peanuts and pistachio with high humidity (p> 0.05). Since other factors such as temperature, pH and chemical composition of pistachio can affect the existence of Aspergillus molds and expression of aflatoxigenic genes, the influence of these factors on existence of Aspergillus molds and genes involved in aflatoxin biosynthesis pathway need to be investigated.
Ali Mohamadi Sani; Mryam Azami; Masoud Yavarmanesh
Abstract
Plants derived products have been used for medicinal purposes for centuries because of antimicrobial activity. In this investigation Antibacterial effect of Hop(Humulus lupulus), the pharmaceutical plant which has an important place in traditional medicine of Iran, was evaluated on some of food borne ...
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Plants derived products have been used for medicinal purposes for centuries because of antimicrobial activity. In this investigation Antibacterial effect of Hop(Humulus lupulus), the pharmaceutical plant which has an important place in traditional medicine of Iran, was evaluated on some of food borne pathogens .This study conducted in order to evaluate antimicrobial effect of Hop water extract compared to Humulune from Hop against Staphylococcus aureus (PTTC1431), Enterobacter aerogenes (PTCC1221), Listeria monocytogenes (PTCC1298) and Salmonella enterica (PTCC1709) by agar disk diffusion and broth microdilution methods. The results indicated that gram positive bacteria were more sensitive to the extracts compared to gram negative bacteria. The minimum inhibitory concentration (MIC) of Humulune and water extract of Hop against Staphylococcus aureus were 0.039 and 0.625 mg/ml respectively. Findings indicate that Humulune had the most antibacterial activity in both methods. The most inhibitory effect was shown against staphylococcus aureus in disk diffusion method (inhibition zone of 17mm). The effect of Humulune were more than water extract of Hop. Results indicate that Hop extract has antibacterial effect and can be used in combinational therapy or as a food preservative
Mahood Sadeghi; Masoud Yavarmanesh; Mostafa Shahidi Noghabi
Abstract
Nowadays, it has demonstrated that viruses can be transmitted by water and foods. Therefore, it causes the research to develop for detecting different viruses in water and foods. Among foods, milk can transfer potentially pathogenic viruses. On the other hand, to achieve every method for recovery and ...
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Nowadays, it has demonstrated that viruses can be transmitted by water and foods. Therefore, it causes the research to develop for detecting different viruses in water and foods. Among foods, milk can transfer potentially pathogenic viruses. On the other hand, to achieve every method for recovery and extraction of viruses in raw milk it needs to know about impact of milk components on viruses. Artificial neural network (ANN) and Adaptive Nero Fuzzy Inference System (ANFIS) can help to estimate recovery efficiency of viruses in raw milk. The objective of this study was to evaluate the application of ANN and Adaptive Nero Fuzzy Inference System (ANFIS) to predict the impact of milk components on recovery and extraction of viral RNA in raw milk. Therefore, to run the model the amount of milk components (casein, whey protein, fat and lactose) and viral RNA extraction were as the input and the output of the network respectively. Also, to evaluate the efficiency of the network for the prediction, variables such as training, validating and test subsets as well as the hidden layers, transfer functions, learning rules and the hidden neurons were used. Based on the results, the best models in ANN were linear sigmoid transfer function, levenberg learning rule (r: 0.919) and linear sigmoid transfer function, levenberg learning rule (r: 0.956) for spiked model solution and (spiked – non spiked) model solution respectively and in Adaptive Nero Fuzzy Inference System (ANFIS) the best model were membership function Gaussian , Adaptive Nero Fuzzy Inference System (ANFIS) model TSK, linear tanh axon transfer functions and momentum learning rule (r: 0.879) and membership function Gaussian, Adaptive Nero Fuzzy Inference System (ANFIS) model TSK, linear axon transfer function, and step learning rule (r: 0.889) for spiked model solution and (spiked – non spiked) model solution respectively.
Ahmad Ehtiati; Fakhri Shahidi; Mohebbat Mohebbi; Masoud Yavarmanesh
Abstract
SMP was substituted by WPC in four levels for preparing reconstituted milk. Two ropy and one nonropy starter cultures was used for Doogh preparation. Yield stress, viscosity, consistency index and pseudoplastic behavior of Doogh increased by increasing WPC content. Results showed that WPC increased colloidal ...
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SMP was substituted by WPC in four levels for preparing reconstituted milk. Two ropy and one nonropy starter cultures was used for Doogh preparation. Yield stress, viscosity, consistency index and pseudoplastic behavior of Doogh increased by increasing WPC content. Results showed that WPC increased colloidal particles dimension and constructed a network which led to a decrease in Doogh phase separation (%32 at the highest level of WPC) during storage. Starter type had no effect on the Doogh stabilization. It does not have any effect on the studied physical properties in the presence of WPC, as well. Adding WPC to milk leads to improve of physical properties and stability of Doogh but using EPS producing starter cultures requires further studies in this field.
Mohammad Reza Edalatian Dovom; Mohammad Bagher Habibi Najafi; Seyed Ali Mortazavi; Majid Hashemi; Masoud Yavarmanesh
Abstract
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 ...
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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.
Masoud Yavarmanesh; Seyed Ali Mortazavi; Mehdi Nasiri mahalati; Javad Barooei
Abstract
Food borne viral infections are recognized increasingly as human illneses. Hepatitis A virus (HAV) is an important pathogen which has been responsible for water and many food – borne outbreeks especially milk . In this study for approaching to best diagnosis method of HAV in milk by ELISA technique, ...
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Food borne viral infections are recognized increasingly as human illneses. Hepatitis A virus (HAV) is an important pathogen which has been responsible for water and many food – borne outbreeks especially milk . In this study for approaching to best diagnosis method of HAV in milk by ELISA technique, various dilutions of HAV antigen (1 ml/L, 10-3 ml/L, 10-6 ml/L, 10-9 ml/L) were added to UHT milk . Various treatments for virus(antigen) isolation, showed that milk with acidic coagulation, following filtration with paper and membrane filters, had the most optical density. It`s indicated that this treatment resulted the best diagnosis . Also it has been revealed that this method has not any sensitivity for quantitative determination of HAV(antigen) in milk.
Key words: diagnosis, Hepatitis A virus(HAV), Milk, ELISA
