نشریه بهداشت مواد غذایی
سال دهم شماره 1 (پیاپی 37، بهار 1399)

The flavor and quality of the Iranian enzymatic cheese are influenced by different factors during its production and storage. The present study was aimed to investigate the effects of various processing conditions, such as pasteurization, retentate treatment, microfiltration (MF), double bactofugation (DBF) and ultrafiltration on the microbial, chemical and textural analysis of the Iranian enzymatic cheese. Our results revealed a significant reduction of the mesophilic bacterial counts (p< 0.05), in all the applied methods of processing. A considerable increase in the numbers of yeasts and molds was observed up to the 21st days of storage (p< 0.05). No obvious changes were observed in the spore counts in 4 °C storage condition, except for the treatment that double bactofugation was excluded. Moreover, the levels of proteins and NPN remained stable. Level of lactose was reduced during the shelfing which was associated with the increased acidity due to the lactose fermentation. In general, the rigidity of samples was gradually increased up to the end of storage (p< 0.05). The current study revealed that concomitant use of different technologies (Hardles’ method) improved the overall acceptance of the cheese and increased its shelf life, the qualities which enhances at 4 °C storage condition.

Q fever with Ricketsia factor is a zoonotic disease having a high pathogenicity. In recent years, it is not just considered as the occupational disease of veterinarian and ranchers. Milk consumption plays an important role in epidemic condition and spread of the disease. This study aimed to examine the prevalence of Coxiella burnetii in bulk cow milk of Gilan province. In this cross-sectional-descriptive study (from summer 2016 to spring 2017), a total of 204 milk samples was collected from the milk collection bulk of Gilan province and tested for detection of the prevalence rate of C. burnetii using  Nested-PCR. From 204 sample of raw milk, 21 samples (10.29%) were positive to C. burnetii presence. The highest rate of contamination was seen in Lahijan (33.3%) and Roodbar (29.4%). The samples collected from Rasht, Talesh, Astaneh and Masal were not found positive for C. burnetii. Examination of the seasonal prevalence of the samples indicated no statistical difference between the different seasons. The results revealed that bulk cow milk could be a potential source of C. burnetii in Iran.

Recently, demands upon the consumption of various seafood are increasing in a human diet. Heavy metals naturally occur in the environment and contamination of foodstuffs are causing great concerns. This study was aimed to investigate the effects of encapsulated and lyophilized Lactobacillus fermentum as probiotic and lactulose on heavy metal residues and fatty acid profile in rainbow trout. Thus, fishes were randomly allocated into three replicates of six different treatments. The experimental groups received basal diet (control group), basal diet plus lactulose, basal diet plus lyophilized L. fermentum and lactulose, basal diet plus encapsulated L. fermentum and lactulose, basal diet plus lyophilized L. fermentum, basal diet plus encapsulated L. fermentum. All the groups were fed three times daily for a period of 56 days. At the end of experiments, samples of the fillet and liver were taken. Our results showed that encapsulated L. fermentum and lactulose as synbiotic, significantly increased n-6 fatty acid in muscles and reduced moisture (p< 0.05). This supplementary diet significantly reduced Pb and Cd residues in muscles and Pb, Zn and Cd residues in liver (p< 0.05). Results showed that using encapsulated L. fermentum and lactulose in the diet improve the overall quality of fish.

Evaluation of probiotic and antifungal properties of the lactic acid bacteria (LAB) isolated from different sourdoughs is so important to prepare microbial cultures for fermentation industries. In the present study, a predominant LAB was isolated from oat sourdough through the back-slopping process, and then it was identified using PCR. Subsequently, probiotic properties of the LAB isolate (including resistance to acid and bile, antibacterial effect, auto and co-aggregations capabilities, antibiotic susceptibility and hemolytic activity), as well as its antifungal activity against Aspergillus niger were studied. Sequencing results of the PCR products led to the identification of Pediococcus pentosaceus as predominant LAB isolated from oat sourdough. The survival rate of the LAB isolates after continuous acid and bile treatment was 59.80% in comparison with the control. The antibacterial effect of the LAB on Bacillus cereus was also significantly (p<0.05) higher than the other studied food-borne pathogenic agents. Crude cell-free supernatant (CFS) of the LAB completely inhibited the growth of B. cereus, but reduced the growth of Salmonella enterica by 65.68%. Meanwhile, naturalized CFS of the LAB had no inhibitory effect on these bacteria. Furthermore, the LAB isolates had a proper co-aggregation with Escherichia coli, and showed resistance towards streptomycin, ciprofloxacin, nalidixic acid and vancomycin antibiotics. The LAB isolates had no hemolytic activity, and its antifungal effect on A. niger was also approved. Accordingly, P. pentosaceus isolate has proper potential to use as probiotic or preservative microbial culture in fermentation industries.

Deoxynivalenol (DON) is one of the mycotoxins produced by Fusarium species. The current study was aimed to compare the efficiency of three cleanup columns (immunoaffinity, MycoSepTM #225, MycoSepTM #227), applied for the determination of DON in cereal products, using high-performance liquid chromatography (HPLC). At first, wheat flour samples were spiked with DON at three concentrations (200, 700, 1200 ng/g), then recovery values were measured after cleanup with the columns. The amount of DON was also measured in 60 samples of cereal products (wheat flour, rice, barley flour, noodles and bread). The results showed that the highest recovery value (between 87.4±2.5 to 95.2±2.2%) was obtained from the immunoaffinity column. However, there was no significant difference between the immunoaffinity column and MycoSep 225. The lowest recovery value was obtained using MycoSep 227 column (P <0.05). The results also showed that 30 samples out of 60 (50%) were contaminated with DON. However, none of the samples exceeded the Iranian Standard limit (1000 ng/g). The highest contamination level (724.3 ng/g) was observed in a rice sample. The study showed that although the immunoaffinity column was more reliable in DON determination, MycoSep 225 showed promising recovery values. In addition, more precaution and measuring controls should be practiced by regulatory agencies to prevent mycotoxin contamination.

Nowadays, coating by natural materials is one of the novel food preservation methods with extensive applications. Cheese is a popular food, however, its high daily intake due to its high salt content may threaten the health of consumers. In this study, instead of stored in brine, the novel method for cheese coating was used with the combination of 2% sodium alginate and 3% carboxymethyl cellulose with wild garlic extract at three concentrations of 0.5, 1 and 1.5%. Two uncoated cheese specimens (stored in or out of brine) were considered as the control groups. Physicochemical (pH, acidity and weight loss), microbial (thermophile, psychrophile, mold and yeast count), and sensory properties of the samples were investigated for 21 days at 4 °C. The results showed that during storage, pH decreased significantly (p< 0.05) while acidity, weight loss and microbial load increased. Coating with various ratios affected all of the sensory properties of the cheese samples. So that the highest score of total acceptance was related to the coating with 1.5% wild garlic extract. According to the results, edible coating based on sodium alginate and carboxymethyl cellulose, containing the wild garlic extract, can be used to increase the shelf life of cheese.

Staphylococcus aureus is one of the most important pathogenic bacteria in the dairy products industry that is capable of biofilm formation. Biofilm formation by these bacteria has been led to resistance to antimicrobial agents. Inactivation of microorganisms using cold atmospheric plasma is one of the new approaches in the food industry. In this study, to evaluate the antibacterial and anti-biofilm effect of cold atmospheric plasma, a dielectric barrier discharge system was used. Twenty isolates of S. aureus from clinical bovine mastitis milk were exposed to plasma from 5 to 20 Sec and their antibacterial activity was estimated by recording the growth zone of inhibition. Plasma treatment was performed punctually for 5 Sec to assess the possible effects of plasma treatment on bacterial biofilm-formation activity after 24 h. The results show that a remarkable reduction in the growth of bacteria by increasing the flow of plasma. Moreover, statistical analysis of the ELISA reader results showed that the exposure of the isolates to plasma, significantly (p< 0.05) reduced the biofilm formation. These results suggest that plasma can be a suitable alternative method for thermal sterilization techniques. However, its application requires further studies to determine the severity and duration of exposure of microorganisms to plasma.

The halophyte Salicornia was recently introduced as a fresh vegetable crop that thrives in extreme salty conditions. In this study, the ash, minerals, heavy metal and nitric and nitrite anions in different parts (root, aerial parts and seeds) of Salicornia europaea L. were evaluated. The results showed that the ash content and sodium in the aerial parts was the highest and in the roots the lowest (P<0.05). But, potassium, copper and calcium between different organs and seed were not significant. While zinc and magnesium in seed and iron in root were higher, and zinc, manganese and magnesium content were lower in the root than other parts (p<0.05). Salicornia roots had the lowest arsenic and cobalt and the highest lead (p<0.05). The seeds containeed the lowest lead, cadmium, mercury and nickel. The aerial parts of this plant also had the least chromium and the highest levels of cadmium, mercury, nickel and cobalt. The mercury in different parts of the Salicornia was lower than the standard value. The lead in the root and cadmium in the aerial parts and chromium, arsenic and nickel in all parts were higher than the limit allowed. The highest nitrate content and the lowest nitrite content in aerial parts and the lowest nitrate content and the highest nitrite content were observed in the seeds (p <0.05). In all studied parts, the nitrate content was found in standard limit. According to the results, aerial parts of Salicornia can be used as a source of calcium, iron, zinc and magnesium.