Zohreh Didar
Abstract
Introduction: Nowadays, edible packaging founds great attention due to environmental issues related to synthetic packaging materials. Gelatin is one of the most commonly ingredients used in edible packaging formulation due to its good barrier properties against gases and UV irradiation. Addition of plant ...
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Introduction: Nowadays, edible packaging founds great attention due to environmental issues related to synthetic packaging materials. Gelatin is one of the most commonly ingredients used in edible packaging formulation due to its good barrier properties against gases and UV irradiation. Addition of plant extracts or essential oils is one approach for confer antimicrobial activity to edible films. The aim of this study was to use different percentages (5-100%) of turmeric hydrosol in the formulation of edible gelatin films and assessing the various properties of the resulted film. Materials and methods: Extraction of turmeric hydrosol was done by Clevenger apparatus. Separation of the essential oil from hydrosol was done by a separating funnel. For preparation of gelatin films, 4g gelatin was dissolved in 100ml distilled water, and glycerol as plasticizer was added at ratio of 25w/w gelatin. In gelatin films included turmeric hydrosol, substitution of turmeric hydrosol instead of distilled water in the ratio of 5-100% was performed. Then, the mixture was poured in plexiglass plates (80×120 mm) and dried at 22ºC, 50% RH for 48h.Texture analysis was carried out using the texture analyzer TA-XT plus. The water vapor permeability (WVP) was measured using gravimetrically method. Light transmission was determined by spectrophotometer jenway 6305 at 200-800 nm wavelength. Morphological assessment was performed by scanning electron microscope (phenom proX). For Fourier-transform infrared spectroscopy analysis, Perkin-Elmer (Spectroma2 model) at 4000-4500 cm-1 frequency, used. Antimicrobial test was done by measurement inhibitory zone (mm) of edible films against Staphylococcus aureus (PTCC 1112), Staphylococcus saprophyticus (PTCC 1440) and Staphylococcus epidermium (PTCC 1435).The studied bacteria (Staphylococcus aureus, Staphylococcus saprophyticus and Staphylococcus epidermium) were purchased from the Iranian Scientific and Industrial Research Center and transferred to the suitable medium in sterile condition and incubated at 37°C for 32 hours. Microbial cells were harvested by centrifugation at 4000 rpm. For the estimation of microbial population, McFarland turbidity method was applied. First, the results from comparing turbidity showed the population of microorganisms was equal to 0/5 McFarland solution (approximately 1/5×108 CFU/ml), then for reaching to the desired microbial population (1/5 × 106 CFU/ml), dilution with physiological saline was done. Agar disc diffusion method was used for assessing the antimicrobial effect of the gelatin films. Gelatin films were cut into a 10mm diameter in aseptic condition using a circular knife and then placed on agar plates inoculated with 100µL of tested bacteria (with approximately 106 CFU/mL). The plates were then incubated (37ºC, 24h). The diameter of the inhibition zone was precisely measured using a digital micrometer (Guanglu model 701-211). Each experiment was performed triplicate. Results and discussion: The results of this study showed that the use of turmeric hydrosol causes significant difference on mechanical and physical properties of related gelatin films (p≤0.01). The stress tension was increased by adding hydrosol to the edible film formulation, but the elongation percentage of the edible film decreased. The highest the stress tension was observed in sample containing 100% hydrosol (33.3 Mpa) but the lowest elongation percentage also was belong to this sample (96%). Addition of hydrosol to film formulation cause increasing of UV-radiation barrier property and reducing the transparency of the film. FTIR analysis of gelatin films included turmeric hydrosol, exhibited the existence of aromatic bonds according to appearing peak at 680cm-1. Structural studies by SEM method, showed uniformity in the structure of different gelatin films and hydrosol addition cause minor changes in the structure of films. The water vapor permeability was influenced by the edible film formulation and by adding different percentages of turmeric hydrosol, the permeability to water vapor, decreased (p≤0.01).Thickness was also affected by gelatin formulation and hydrosol caused reduction the thickness. Antimicrobial assessments showed that the addition of turmeric hydrosol cause inhibitory effects against studied staphylococcus strains. Staphylococcus aureus and Staphylococcus saprophyticus showed the highest susceptibility to hydrosol included films (inhibition zone equal to 37 mm for gelatin film included 100% turmeric hydrosol).
Zohreh Didar
Abstract
Introduction: Metal oxide nanoparticles have unique physical and chemical properties. These components have shown antimicrobial effects against a wide range of microorganisms. In order to improve the physical properties of metal oxide nanoparticles, doping other elements with metal oxide nanoparticles ...
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Introduction: Metal oxide nanoparticles have unique physical and chemical properties. These components have shown antimicrobial effects against a wide range of microorganisms. In order to improve the physical properties of metal oxide nanoparticles, doping other elements with metal oxide nanoparticles is an effective way. Bacillus cereus is a gram-positive bacteria causing food-borne diseases. In this study, the antimicrobial effects of doped zinc oxide nanoparticles with manganese or iron on Bacillus cereus have been studied. To investigate the synergistic effects of the combined nanoparticles with two common biocides, including hydrogen peroxide and sodium hypochlorite, have been used.
Materials and methods: Co- precipitation method was used to prepare nanoparticles of manganese-zinc oxide and iron-zinc oxide. In this method, zinc sulfate and manganese sulfate were used to prepare manganese-zinc oxide and iron sulfate and zinc sulfate are used for Zn- Fe doped nanoparticles. After preparing the sulfate solutions, the sulfate solutions were mixed and placed in an ultrasonic apparatus at a frequency of 57 kHz for 2 hours at 50ºC. Then, it was stirred at 80°C. A solution of NaOH was added until the pH of the solution reached 12. In these conditions, the mixing was done for 30 minutes. The solution was placed at ambient temperature for 18 hours. Then the centrifuge was performed to separate the sediment. Purification was done through washing with distilled water and ethanol. The precipitates were dried in the vacuum oven. In this way, the doped nanoparticles of manganese-zinc oxide and iron-zinc oxide were obtained. The Fourier transform infrared spectrum (FTIR) was carried out by the Perkin-Elmer apparatus of the Spectroma2 model, using a dry potassium bromide tablet at a frequency range of 4500-4000 cm-1. The X-ray diffraction was tested using the Phillips PW1820 from 2º to 80º. Structure of produced nanoparticles was assessed by the HITACHI electron microscope, the H-7500 model, by placing a drop of nanoparticles dissolved in methanol on a special lining with carbon coating and air drying, and performing microscopic images using an electron microscope in 100kv. The bacteria used in this study included Bacillus cereus (PTCC 1665) was purchased from the Iranian Scientific and Industrial Research Center and was transferred to the BHI medium in sterile condition and incubated for 32 hours at a temperature of 32°C. Microbial cells were isolated by centrifugation at 4000 rpm. McFarland's method was used for determining the bacterial population. Dilution was carried out to reach a population of about 106 CFU/ml. Agar disc diffusion method was used for assessing the antimicrobial effect of the doped nanoparticles alone or in combination with tested biocides (hydrogen peroxide, sodium hypochlorite). At first, 106 CFU/ml of Bacillus cereus were inoculated on the surface of Blood Agar. Then, 5, 10, 20, 30, 50, 100 and 200 mg/L of each of the nanoparticles were placed on the surface of the culture medium and then the plates was incubated at 37°C for 24 hours. Inhibition zone was considered as antibacterial activity. In order to investigate synergistic effects, inhibitory fraction index test was calculated. All experiments were performed in three replications. Statistical analyzes were performed using STATISTICA software.
Results and discussion: Results obtained from X-ray and FTIR analysis of doped nanoparticles confirmed that co- precipitation is a suitable method for producing doped nanoparticles of zinc oxide. TEM analysis of produced nanoparticles also affirm formation of doped nanoparticles of zinc oxide with manganese and iron. The results of antimicrobial tests showed that Mn-Zn oxide nanoparticles have more antimicrobial effects on Bacillus cereus than zinc oxide (32mm inhibition zone) whereas Fe- Zn oxide nanoparticles cause inhibition zone about 12 mm. In addition, both doped nanoparticles have more antimicrobial effects than zinc oxide nanoparticles alone, resulted in doping process improves antimicrobial properties of zinc oxide. The synergistic effects of synthetic nanoparticles in the combination of two common antimicrobial agents, including hydrogen peroxide and sodium hypochlorite, have been identified. Both nanoparticles show synergistic effects in combination with two tested biocides (especially in high concentrations). A mixture of two biocides with nanoparticles increases their antimicrobial properties. Manganese-zinc oxide nanoparticles with hydrogen peroxide and sodium hypochlorite showed a partial synergistic effect at low concentrations (5 + 20) and a complete synergistic effect at higher concentrations. In the case of iron-zinc oxide, combination of this nanoparticle with hydrogen peroxide and sodium hypochlorite, has complete synergistic effects at high concentration (100 + 200) and at other conditions, shows partial synergistic effects.
Zohreh Didar; Seyed Mahdi Seyedain Ardebili; Maryam Mizani; Mohammad Hossein Hadad Khodaparast; Ali Reaz Ghaemi
Abstract
Usage of different lactic acid bacteria strain is one of the reduction methods in phytic acid content of bakery products. In this study the effect of making sourdough with L. plantarum and L. reuteri with DY=160 and DY=200 and replacement ratio 10, 20 and 30% instead of flour in dough formulation on ...
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Usage of different lactic acid bacteria strain is one of the reduction methods in phytic acid content of bakery products. In this study the effect of making sourdough with L. plantarum and L. reuteri with DY=160 and DY=200 and replacement ratio 10, 20 and 30% instead of flour in dough formulation on phytic acid content of Lavash bread was investigated. The highest decrease in phytic acid content is related to using sourdough involved L. plantarum with DY=200 and 30% replacement of sourdough (44.06%).
Usage of sourdough causes flavor and chew ability modification in bread. The best flavor is related to bread which is made of sourdough involved L. plantarum with DY=200 and 30% replacement. But biophysical properties containing texture, form, shape, and up and down surface in this sourdough application gain lower score than bread which is made of yeast.
Keywords: Phytic acid, Lavash bread, Lactobacillus plantarum, Lactobacillus reuteri
