نشریه بهداشت مواد غذایی
سال نهم شماره 2 (پیاپی 34، تابستان 1398)

Measuring the total microbial count of cow minced meat with the conventional method and comparing the result with standard limits is one of the routine tests. Achieving the results of total microbial count in minimum time is really important for confidence from the hygienic quality of products. So impedance- splitting method as a new technique for this purpose was considered in order to receive the results in less time and as soon as possible. The main purpose of the study was to evaluate the correlation between impedance detection times (IDT in hrs), total microbial population (log CFU/g), total volatile nitrogen (TVN) and pH of minced meat. Totally 80 minced meat samples were collected and examined for the total microbial count by reference and impedance - splitting methods, also total volatile nitrogen and pH were measured based on the recommendations of Iran's Standard Institute and Industrial Investigation. Then the calibration curves of methods and their equations were obtained by using Excel software. The calibration curves of methods were elaborated for total microbial count and impedance detection time, demonstrating a good correlation between the two methods in mince neat samples equal to %93/39. Also according to the calibration curves, the correlation between impedance detection time and total volatile nitrogen in all of the samples were equal to %69.8. Also, the correlation between total microbial count and pH was equal to %71/4. According to above-mentioned correlation values, the impedance technique could be only recommended as an alternative method in evaluating the microbial load of the minced meat.

In this research, the effect of gamma irradiation, thyme essential oil (EO) and vacuum packaging treatments on fresh shrimp for a period of 15 days at 4°C during storage was investigated. For this purpose, two concentrations of EO (0.4 and 0.8% v/w) and two doses of radiation (2.5 and 3.5 KGy) were used. Treated shrimps and control sample were subjected to chemical (pH, total volatile basic nitrogen, free fatty acids, peroxide index, thiobarbituric acid reactive substances and color indexes), microbiological (bacteria total count, psychrophilic bacteria and  Escherichia coli) and sensory evaluation and analyses performed on certain days (0, 5, 10 and 15th) of storage. The obtained results showed that pH, FFA, peroxide, TBARS and TVB-N values of all treatments increased in the duration of storage, significantly (p<0.05). Microbial load in all treatments also increased over time. Bacterial growth delayed growing in samples by using of combination of thyme oil, gamma radiation and vacuum packaging. At first, adding thyme EO leds to decrease L* index, but at high concentration of EO (0.8%), color change was decreased significantly (p<0.05). The results of sensory evaluation showed that different treatments had significant effect on sensory parameters of shrimp (p<0.05). Finally, the shrimps treated with combination of vacuum packaging, 0.8% (v/w) EO and 2.5 KGy can be introduced as the best treatment.

The presence of trace amount of Tetra -butyl hydroquinone or its metabolite, Tetra -butyl benzoquinone (TBQ), may inhibit cell proliferation and cause biologic abnormalities due to the high prevalence of thiolate groups of proteins or cell walls. The aim of this study was to fabrication an electrochemical nanosensor based on molecular imprinted polymer to detection of TBQ in edible oil. This study was a methodologic study. The statistical population included edible oil samples containing TBQ. The effect of different factors such as amount of MIP and MWCNT for production of ceramic carbon electrodes as well as pH of preconcentration solution and the incubation time of the prepared nanosensor in the solution on the oxidation signal of TBQ was optimized by response surface methodology. Differential pulsed voltammetry has been used to determine the TBQ in oil samples. The Morphologies of MIP and prepared sensors were described by scanning electron microscopy. Optimal conditions for the separation and determination of TBQ in edible oil, including 10 mg of multiwall carbon nanotube, 30 mg of MIP for preparing a modified carbon ceramic electrode, and 8 minutes as incubation time in a 0.1 M phosphate buffer solution with pH 10 was obtained. The proposed method is capable of detecting TBQ in edible oil samples at a concentration range of 6 - 680 nM with a detection limit of 3.1 nM. Based on the results, the proposed sensor can be used as a suitable tool for determination of TBQ in edible oil samples in industries and laboratories.

Plants are valuable sources of different antioxidant and antimicrobial compounds. The composition and structure of the functional groups of essential oils and extracts play an important role in their antioxidant and antimicrobial activity. Prosopis farcta is a spice of Leguminosae family and Mimosoideae subfamily, an aborigine to the dry and semi-dried regions of Asia, Africa and America. In this study, the root extract of Prosopis farcta prepared by soxhlet extractor and ethanol 70% solvent. The extraction yield was estimated at 1.85%. Total phenol and flavonoids compounds were calculated 178.14 ± 0.17 mg Gallic acid/g and 94.33 ± 0.77 mg Quercetin/g, respectively. Phenolic compounds comprised 11.98% of the total chemical composition of the extract. IC50 for root extract and BHT (synthetic antioxidant) was determined 2.45 μg/ml and 1.98 μg/ml, respectively. In the β-carotene-linoleic acid system, the average antioxidant activity reported 39.25% for root extract and 57.13% for the BHT. Among 250, 500 and 1000 ppm concentrations of the extract, 1000 ppm showed the best antioxidant effect in soybean oil for 12 days storage at 50°C. Staphylococcus aureus (with MIC 200 µg/ml and MBC 350 µg/ml) showed the most sensitivity in comparison with the two gram-negative bacteria, Salmonella Typhimurium and Escherichia coli. The results of this study showed that the hydro-ethanolic root extract of Prosopis farcta had suitable antimicrobial and antioxidant activity.

Aflatoxins are, a group of closely related carcinogenic metabolites produced by certain species of Aspergillus. The objective of this study was to detect the level of aflatoxins in nuts. A total of 80 samples of nuts including, pistachio (20), almond (20), hazelnut (20) and walnut (20) were collected analyzed for AFB and AFG  in Isfahan in 2016 using HPLC. The aflatoxins B1, B2, G1, G2 and Total were found in 2.5%, 5.5%, 5.7%,7.2%, and 10% of the analyzed sample by an average concentration of 8.32, 5.635, 3.067, 1.705 and 10.375 ppb, respectively. The concentration of AFB1 in 66.67% and the concentration of AFT in 37.5%  from positive samples Iran were higher standard (5ppm). The percentage of pistachio AF-positive nuts samples was significantly (p<0.05) more than other nuts (almond, hazelnut and walnut). The results showed that contamination of nuts especially pistachio to aflatoxins not good and can compromising consumer health.

In this experimental study, the effect of pH (2, 4, 11), temperature (4, 85, 121 oC) and bile salt (0.3, 0.6, 1%) treatments on inhibitory potential of cell free supernatant (CFS) obtained from barley sourdough dominant LAB (Pediococcus stilesii, Weissella cibaria, Lactobacillus brevis and Lactobacillus curieae) isolates, against B. subtilis were investigated based on microdilution method in comparison to untreated CFS. Safety of LAB isolates were also assessed by control of changes in serum parameters and liver enzymes in mice fed with them. Results were statistically analyzed by one way analysis of variance.    Based on results, LAB CFS had antagonistic activity against B. subtilis. Inhibitory effects of the CFS under pH and temperature treatments were decreased, but under bile salt treatment were increased. Changes in serum parameters and liver enzymes in mice fed with LAB isolates were also in normal ranges and so on, safety of the LAB isolates were approved. By considering the antagonistic activity of LAB CFS under pH, temperature and salt treatments, against B. subtilis it is possible to use from the CFS as a biopreservative in food processing chain.

Mycotoxin contamination of foodstuff and its transmission to consumers are extremely important from the public health point of view. Aflatoxin M1 (AFM1) is a hepatocarcinogenic toxin found in the milk of animals that have consumed feeds contaminated with aflatoxin B1. The aim of this study was to determine the level of AFM1 in raw milk at traditional dairy retails of the east of Mazandaran province. A total of 80 cow raw milk samples was randomly collected from retails of 10 cities of Mazandaran during March 2015. The level of AFM1 was measured by ELISA assay using commercial kits and a microplate reader. All raw milk samples contained measurable amounts of AFM1. The results showed that 6.25% of the total samples had higher concentrations permitted by the Institute of Standards and Industrial Research of Iran; moreover, 17.5% of the samples were contaminated with higher concentrations of AFM1 than the maximum allowed limit set by the European Commission. Results revealed any significant relationship in the AFM1 concentrations between the sampling cities. According to the outcomes, it can be concluded that adequate control measures at the farm level may have resulted in reduced concentrations of AFM1 in raw milk of Mazandaran province; however, frequent monitoring is crucial.

Some zoonotic protozoa can be easily transmitted through food and water and cause serious illnesses in humans and animals. Because these pathogenic agents have some characteristics of an effective biological agent for example, latent period, low infectious doses, high resistance to disinfectants, they can play a role as an unknown biological agent in bioterrorism. Considering the increasing threats of bioterrorism, biological agents and their use by some colonial countries, it is necessary to identify and recognize these unknown agents and ways to prevent them. Based on a systematic study some keywords such as” bioterrorism”, “biologic”, and “protozoa zoonosis”, parasite” and names of some waterborne and foodborne parasites were searched in reliable information databases and then the related topics were studied carefully. The results of this study show that in addition to bacteria, viruses and their toxins, zoonotic protozoa such as Giardia intestinalis, Entamoeba histolytica, Cryptosporidium parvum, and Toxoplasma gondii which can be transmitted through food and water, can act as biologically hazardous agents in bioterrorism. Because these zoonotic protozoa are resistant to some disinfectants, for example, chlorine and low temperatures, so the only way to deal with these biological agents at times of crisis is to boil the water for 10-15 min at 60 ° C as well as to cook completely those food materials with the probability of contamination.