نشریه بهداشت مواد غذایی
سال دهم شماره 2 (پیاپی 38، تابستان 1399)

Metal particles are added to polymers used in the food packaging to improve their mechanical and antimicrobial properties. In this study, the antimicrobial properties of low-density polyethylene nanocomposite (LDPE) containing 17.5%, 12.5%, 7.5%, and 2.5% silver nanoparticles were investigated. UV-Visible, SEM, and XRD tests were used to confirmation of the synthesis of silver nanoparticles, characterization of silver particle distribution, and silver crystal structure. Crystal nanoparticles with an average size of 20 nanometers were approved. To evaluate the antimicrobial properties of silver nanocomposites, bacterial growth in the presence of nanosilver films with the mentioned percentages was measured by optical density (OD) method via spectrophotometer (600 nm). Besides, the migration of nanoparticles was measured. The results showed that the coating containing 17.5% and 2.5% nanosilver had the highest and the lowest effect, respectively and in comparison to the other groups. Also, comparing the effect of coatings on two types of food pathogens, E. coli and S. aureus, showed that the effect of coatings on S. aureus was higher. The results showed a correlation between the percentage of silver nanoparticles used and antimicrobial properties. Furthermore, with increasing the percentage of silver nanoparticles, the releasing rate of nanoparticles from the coating increased. Finally, due to the migration of silver nanoparticles from all four types of nanocomposite coatings in the permitted range, 17.5% coating was selected as the most efficient one.

In determining the quality of oils, heavy metal content, physical-chemical indices, and fatty acid profile, especially trans fatty acids are important factors. In this study, animal oil samples of different regions of Ilam province studied. After digestion and extraction by microwave-assisted acid digestion, the heavy metals content of the samples measured by an improved flame atomic absorption spectroscopy method. Moreover, after extraction and derivatization of the oils, the fatty acid profile was analyzed by gas chromatography. To facilitate the conclusion of the data obtained, samples of different regions of the province are divided into three parts: northern, southern, and central cities. According to the results, copper, cobalt, and chromium levels were reported in the range of 0.04-4.47, 0.02-2.33, and 0.02-3.54 mg/kg, respectively, which were below the maximum permissible levels. It was revealed that using the modified gas chromatography method, it is possible to separate and measure 27 fatty acids simultaneously. Besides, an acceptable degree of extraction of oleic and linoleic acid is extracted to calculate the cis and trans isomers, which was achieved.

Crops such as fruits as raw materials for the production of fruit juices are affected by different pests that are regularly used to combat these agents in agriculture activities. Some of these substances not only remain on the surface of crops but also penetrate their tissues, as most of the crops exposed to pesticides contain amounts of pesticide residues that enter the consumer's body along with foods. For this reason, the use of precise and efficient methods in evaluating the residuals amounts of these compounds in food products is of great value. In this research, a combination of air-assisted liquid-liquid microextraction and liquid-liquid microextraction with solidification of floating organic drop methods has developed for extraction and preconcentration of some of the widely used organophosphorus pesticides used in Iran (Diazinon, Chlorpyrifos, Phosalone,  Parathion- methyl and Azinphos-methyl) from juice samples before their analysis by high-performance liquid chromatography. Under optimal conditions, 32 μl of menthol as the extraction solvent and 75 μl acetonitrile as dispersive solvent at a temperature of 60 °C used to extract the analytes. The proposed method is simple, reliable, and inexpensive and yields optimal values ​​for extraction efficiency so that under optimized conditions the recoveries ranging from 61 to 79%. RSD% was in range 4.6 to 6.9, indicating high reproducibility of the proposed method. Other advantages of this method include low organic solvents consumption and short analysis time.

Some probiotic microorganisms can prevent the growth of pathogenic microorganisms in addition to improve the intestinal microbial balance. In this study, the qualitative characteristics and viability of two foodborne pathogens (Staphylococcus aureus and Escherichia coli) lactic cheese were investigated. For this purpose, in the first stage, four types of lactic cheese (60 samples) were produced as probiotics (containing Lactobacillus casei and Lactobacillus acidophilus) and non-probiotic with 3 and 4.5% fat milk in three replicates, and the quality parameters were evaluated at days 0, 14, 28, 42 and 56. Then, 12 types of lactic cheeses [(probiotic/non-probiotic) fat percentage (3 and 4.5%) and pathogenic microorganisms (absence, presence of Staphylococcus aureus or Escherichia coli)] (180 samples) were prepared and the viability of pathogenic microorganisms in the presence of probiotic was evaluated on days 0, 7, 14, 28 and 35. The addition of probiotics to lactic cheese significantly reduced fatty acid oxidation and increased acidity and volatile nitrogen compounds (P < 0.05). The addition of probiotics to high-fat cheeses increased non-protein nitrogen compounds but decreased in low-fat cheeses. The addition of probiotic to lactic cheese significantly reduced the growth of S. aureus and E. coli (P < 0.05). Increasing fat percent did not show a significant effect on bacterial growth inhibition by probiotics (P < 0.05). Due to the effects of adding probiotics on decreasing the pathogenic bacterial growth and not significantly altering the sensory properties of lactic cheese, it is recommended to use these probiotics in the production of low-fat lactic cheese.

Heavy metals can easily contaminate the aquatic environment, especially shrimp. Considering the high nutritional value of shrimp and the importance of assessing its wholesomeness, this study aimed to determine the amount of some heavy metals (zinc, lead, arsenic, cadmium, nickel, copper, chromium, mercury, manganese, and titanium) and Polycyclic aromatic hydrocarbon in shrimp samples in Tehran, during winter of 2017. A total of 120 samples of shrimp packaged from 10 equal weight packages with similar production date and size which packed by 5 different companies randomly sampled. To determine the amount of heavy metal concentration, Atomic absorption spectrophotometry and to determine polycyclic aromatic hydrocarbon gas chromatography were used. All of the heavy metals measured in this experiment were found below the standard specified by the World Health Organization. The highest mean concentrations of heavy metals were related to zinc (6193.4 ppb), copper (1597 ppb), and arsenic (496 ppb), respectively, and the lowest mean concentrations were related to cadmium (4.8 ppb). Naphthalene (1.2ppb), acenphetylene (0.14 ppb), chrysene (7.6 ppb), and acenaphthene (5.32ppb) were present in the samples of collected shrimp, the values of which were determined higher than standard except for acenphetylene. Additionally, there was no significant difference between heavy metals and PAHs in cultivated and marine samples. In general, the consumption of these shrimps is not dangerous for humans in terms of heavy metals. However, due to the possibility of transmitting PAHs through the human food chain, contamination with PAHs can be considered as a warning for excessive consumption of shrimp.

The use of herbal essential oils can inhibit bacterial growth and proliferation. In this investigation, the chemical composition and antimicrobial effects of essential oils of Oliveria decumbens on culture media and hamburger have been studied. GC/MS analysis identified 12 components in the essential oils of Oliveria decumbens. The antimicrobial activity of the essential oils was investigated against Staphylococcus aureus and Escherichia coli using disc diffusion and well plate method. The experiment was a factorial form of a completely randomized design with 3 levels in essential oil concentration (0, 0.32, and 1.25 µl/g) in 4 periods (1, 20, 40, and 60 days) with 3 replications on S. aureus, E. coli, mold, yeast and total count in hamburger. The most important identified compounds in the essential oils of Oliveria decumbens were phenolic and aldehyde compounds. Minimum inhibition concentrations of Oliveria decumbens essential oils against S. aureus and E. coli were 0.32 µl/ml and 0.625 µl/ml, respectively. Besides, the number of microorganisms decreased with increasing concentrations of essential oils of Oliveria decumbens. There was no significant difference between the control and concentrations of 0.32 µl/g in E. coli count but in all types of microorganisms, the highest decrease was observed in the concentration of 1.25 µl/g (p < /em><0.05). The high amount of aldehydes and phenols in Oliveria decumbens essential oils may be a reason for antimicrobial effects of the plant essential oils that can be considered as a natural source of preservative in food.

Materials in nanoscale dimensions have a high surface-to-volume ratio, and thus have better reactions with other materials. The development of nanotechnology over the past decades has opened up opportunities for discovering the antibacterial effects of metallic nanoparticles. In this study, the antibacterial properties of nanoparticles on aluminate (ZnAl2O4) were studied on Escherichia coli and Pseudomonas aeruginosa bacteria. Antibacterial activity was assessed by using the disk diffusion method on agar using nanoparticles on synthesized aluminate. The non-growth halo diameter indicates the sensitivity of bacteria to antimicrobials. The minimum inhibitory concentration of bacterial growth (MIC) and minimum bacterial leaching concentration (MBC) was measured by microdilution in sterile tubes. Statistical analysis was done by T-test. The results of this study showed that Pseudomonas aeruginosa sensitivity (16.06±1.8mm) was higher than E. coli (11.64±2.2mm) (p < 0.05). The minimum inhibitory concentration (MIC) and bactericidal concentration MBC of bacteria Pseudomonas aeruginosa and Escherichia coli bacteria MIC and MBC was lacking. According to the results obtained in this study, we conclude that Pseudomonas aeruginosa was more sensitive to alumina than that of E. coli against nanoparticles.

Among dairy products, ice cream is very popular all over the world. Therefore, in this research, the possibility of producing probiotic ice cream containing Aloe vera gel was investigated. For this purpose, Aloe vera gel at concentrations of 0%, 5%, 10%, and 15% was added to ice cream samples and its effect on the survival of Lactobacillus plantarum was investigated. Besides, some chemical and sensory properties of ice cream were evaluated. The results of this study showed that the addition of Aloe vera gel did not have any significant effect on the acidity, moisture, and fat content of probiotic ice cream samples, but the microbial count and sensory properties of this product were significantly (p < 0.05) affected. During storage, in the samples containing 10% and 15% Aloe vera gel, the number of probiotic bacteria increased to 8.15 and 8.19 log CFU/ml, respectively. The overall sensory evaluation of ice cream samples showed that the highest sensory rating was related to the treatment containing 10% Aloe vera gel. It was concluded that considering the sensory acceptance and survival of probiotic bacteria L. plantarum, the ice cream containing 10% Aloe vera gel was the best treatment.