Journal of Food Quality and Hazards Control

38-39

Authors: E. Dimitrieska-Stojkovikj

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41-48

Authors: M. Carvalho, H. Albano, P. Teixeira

Background: Plant-derived Essential Oils (EOs) have shown remarkable antimicrobial activity against spoilage and pathogenic microorganisms isolated from food products. The objective of the current study was to determine in vitro antimicrobial effects of selected EOs against these microorganisms. Methods: Antimicrobial activity of EOs against food-borne and spoilage microorganisms was screened by disk diffusion assay; then, the Minimum Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) were determined. Statistical analysis was done using SPSS 23.0 software for Windows. Results: Oregano and thyme EOs showed the highest antimicrobial activity and the lowest MICs, while anise, fennel, garlic, and ginger showed a lower activity with significant differences (p<0.05). It was demonstrated that Salmonella Typhimurium, Escherichia coli, Proteus mirabilis, and Yersinia enterocolitica were the most sensitive bacteria to all the EOs tested (p<0.05). Among Gram-positive bacteria, Listeria innocua was demonstrated to be the most sensitive to most of the EOs (p<0.05). Furthermore, Staphylococcus aureus and Listeria monocytogenes were shown to be more sensitive than Enterococcus spp. (p<0.05). Yeasts were significantly (p<0.05) more sensitive than bacteria and were inhibited by most of the EOs. Conclusion: The use of the analyzed EOs may be interesting to food processors because of their antimicrobial properties. However, it is necessary to test their use in food products and gauge their sensory implications.

54-60

Authors: Sh. Sotudeh, M. Rabbani Khorasgani , Z. Etemadifar, S.H. Zarkesh-Esfahani

Background: Nowadays, colostrum has been known as a considerable and valuable by-product of large-scale dairy production in the world. The main objective of this study was to evaluate the effects of pasteurization, spray-drying and freeze-drying methods on bacterial loads and Immunoglobulin G (IgG) level of bovine colostrums. Methods: Colostrum samples were collected from the first milking postpartum of Iranian Holstein dairy cattle farms. The samples were treated by pasteurization (60 °C for 30 min and 55 °C for 60 min), spray-drying and freeze-drying methods. Standard Plate Counts (SPC), Escherichia coli count, and Total Coliform Count (TCC) were analyzed at days 1, 10, 20, and 30 of storage. Also, IgG level were assessed at the end of 30-day storage. Statistical analysis was performed using SPSS 17.0 (Chicago, IL, USA) software. Results: Although all four treatments showed direct impact on reduction of SPC, TCC, and E. coli count in colostrum stored at 1, 10, 20, and 30 days, but the spray-drying and freeze-drying methods were significantly (p<0.05) more effective to reduce microbial loads. The mean IgG levels of the samples were 60.35 mg/ml for untreated samples (control); 30.65±6.95 mg/ml for spray-dried treatment; 36.97±6.79 mg/ml for freeze-dried treatment; 28.12±6.53 mg/ml for heated treatment at 60 °C/30 min; and 34.97±9.80 mg/ml for heated treatment at 55 °C/60 min. All four treatments resulted in significant (p<0.05) reduction of the IgG levels. Conclusion: Considering the obtained results, it seems that freeze-drying and spray-drying methods could be more effective than pasteurization ones to enhance quality and shelf life of bovine colostrum for a long time.

72-76

Authors: M.M. Soltan Dallal, R. Mazaheri Nezhad Fard, M.K. Sharifi-Yazdi

Background: Staphylococcus aureus, a Gram-positive bacterium, is the most prevalent food-borne pathogen in most regions of the world. The current study was carried out with the aim of S. aureus isolation from shrimps sold in Tehran, Iran. Furthermore, the genes of mecA as indicator of methicillin-resistant S. aureus, sea, seb, and tsst encoding enterotoxins were studied in the S. aureus isolates. Methods: Totally, 150 fresh and 150 frozen shrimp samples were collected from seafood retailers in Tehran. Isolation of S. aureus from the samples was carried out using conventional methods. The target genes were identified using polymerase chain reaction technique. Data were statistically analyzed using SPSS v. 11.5 software. Results: Out of 150 fresh and 150 frozen samples, 84 samples (28%) were contaminated with S. aureus. The contamination rate in fresh samples (22%) was significantly (p<0.05) lower than in frozen samples (34%). Totally, prevalence rates of sea, seb, tsst, and mecA genes in the isolates were 39.3, 15.5, 4.8, and 28.6%, respectively showing significant (p<0.05) differences. Conclusion: High prevalence rates of enterotoxigenic and also antibiotic resistance genes in S. aureus isolated from shrimp samples in the current study highlighted worries about risk of staphylococcal food poisoning in Iranian shrimp consumers.