نشریه بهداشت مواد غذایی
سال پنجم شماره 1 (پیاپی 17، بهار 1394)

This research aimed to evaluate the antibacterial effect of vanillin on Escherichia coli and Staphylococcus aureus using agar diffusion technique. For this reason, edible films were manufactured from wheat gluten containing 0.5%, 1%, 2% and 4% w/w. The inhibitory effect of the films was assessed based on the surface area of inhibition zone. According to the results, 0.5% of vanillin had no inhibitory effect neither on E. coli nor S. aureus. However, vanillin concentrations higher than 1% could have antibacterial effect on E. coli and S. aureus. Results revealed that with the increasing of vanillin concentration, the surface area of inhibition zone was increased. Moreover, the increasing of vanillin concentration could lead to an increase in the extensibility and elongation of the gluten film. Interpenetrating network cross-linking mechanisms might account for the Schiff base reaction between gluten and vanillin. Although significantly different inhibitory effect was observed between E. coli and S. aureus, the vanillin films were effective on both bacteria.

This study aimed to assess the behavior of various strains of Yersinia enterocolitica in ultra-filtered (UF) cheese and to evaluate the inhibitory effect of lactic starter bacteria on survival of Y. enterocolitica. To this end, pasteurized ultra-filtered milk was inoculated with 3 log cfu/g of two standard strains (DSM 11502 and DSM 9499) and one native strain of Y. enterocolitica. UF cheese samples were produced with and without starter culture. Enumeration of Y. enterocolitica was performed at the time of inoculation, after incubation time and during the 2-months storage period on CIN agar. The enumerated colonies were confirmed by PCR. Results revealed that after incubation, the populations of Y. enterocolitica in both groups increased by 4.14 log cfu/g (P < 0.01). However, during the storage period the number of Y. enterocolitica decreased only in the samples made with starter cultures. pH values revealed a significant difference (P < 0.01) between the samples made with and without starter culture; therefore, it seems that acidic pH is the major factor inhibiting the survival of Y. enterocolitica in UF cheese. Besides, a significantly (P < 0.01) different behavior was observed among native and standard strains. Considering the inhibitory effect of starter bacteria,it seems that creation of proper conditions in terms of temperature and the time necessary for proliferation and activity of starter bacteria or application of cultures capable of producing antagonistic products can be effective in controlling possible microbial contaminations along with the development of desirable aroma and texture in UF cheese.

Koozeh cheese is of the local traditional cheeses of Azerbaijan and Kurdistan areas of Iran, and this cheese has high consumption among the people of these regions. Listeria monocytogenes is a food borne pathogen, and because of its growth at refrigeration temperatures has great concern in public health. In the present research, prevalence rate of L. monocytogenes in Koozeh cheeses of Urmia retails was surveyed. Moreover, antimicrobial susceptibility of the isolates was studied. One hundred samples of Koozeh cheese were collected randomly from Urmia retails in the spring of 2013. Samples were cultured in L-PALCAM Listeria selective enrichment broth with supplement. The enriched samples were transferred to PALCAM Listeria selective agar with antibiotics. For the identification of Listeria species, specific biochemical tests were performed. Antibiotic susceptibility of L. monocytogenes isolates was determined by disk diffusion method using penicillin G, chloramphenicol, ceftriaxone, erythromycin, tetracycline, and gentamicin. Among the 100 tested samples, L. monocytogenes was isolated from 3 of the samples. Antibiogram results showed that all L. monocytogenes isolates were susceptible to the tested antibiotics. However, tetracycline, penicillin and erythromycin were shown larger diameter of inhibition zone than the others. Although the prevalence rate of L. monocytogenes in Koozeh cheeses was low, its capability to growth in refrigerator conditions along with the pathogenicity of the bacterium to humans, hygienic production and distribution of these cheeses are recommended.

The aim of this study was to assess the effect of gutting on sensory, microbial and chemical characteristics, and fatty acid profile of rainbow trout (Oncorhynchus mykiss) during storage at -18 º C. To this end, 42 rainbow trout were prepared and divided into two groups. First group selected as whole fish and the other group were gutted, washed and were placed in selofan-pack and then were frozen at -18 °C. Afterwards, the quality characteristics (TVB-N, TBA, and PV), nutrient compounds (protein, fat, moisture and ash), fatty acid profiles, microbial community (total count and psychrophilic bacteria) and sensory indices were evaluated during 3 months of frozen storage. The results showed a different between two groups in moisture contents, PV, TBA and TVB-N parameters during storage (P< 0.05). Evaluation of fatty acid profile revealed 15 fatty acids. In both groups, the MUFA, SFA and PUFA were the most abundant fatty acids, respectively. During the storage period, the composition of fatty acids was found to be different between the two groups. Although microbial examinations showed no significant difference in the population of psychrophilic bacteria among the two groups, the load of total bacteria was found significantly (P< 0.05) different. Sensory evaluations revealed significant (P< 0.05) difference among all indices between the gutted and whole fishes. In addition, the texture and appearance changes were remarkable in gutted fish, meanwhile the odor and branch appearance were adequately preserved.

Food hygiene is considered as an indication of community health. For this reason, consumers need to have enough information about the safe methods of providing, storage and preparation of foods. This study aimed to assess the knowledge and attitude towards food safety among university students. The survey research was used to study 400 students at the four universities of Gorgan city during 2013. The universities included Gorgan Azad University, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan Medical University and Golestan University. The data collection instrument was a questionnaire which its validity and reliability were verified by face validity and Cronbach's alpha coefficient, respectively. The results showed that for the university students, families and TV programs are the main sources for gaining information about food safety. Furthermore, knowledge and attitude of students towards food safety was determined as "fairly good" and "good" respectively. Female students had more knowledge and favorable attitudes towards food safety than male students. Based on results, food safety knowledge was not related to age, place of birth and residence and the type of housing; however it is associated to the level of parent's education and occupation. Attitude towards food safety also was found to be associated with birthplace and studying degree. It was concluded that it is necessary to deliver the educational programs about food safety for the university students along with the installation of food borne disease surveillance system.

Providing safe foods resistant to pathogens as well as replacing chemical preservatives with natural compounds including essential oils has attracted great attention in current studies. The purpose of this study was to investigate the antimicrobial properties of clove’s essential oil on hamburger. For this reason, clove essential oil was extracted by Clevenger apparatus method. Minimum Inhibitory Concentration (MIC) of Staphylococcus aureus, Escherichia coli, Candida albicans and Aspergillus niger was measured. The antimicrobial effect of the essence in the concentrations of 0.0015%, 0.01%, 0.1% and 0.15% was examined on hamburger. The samples were examined at 0, 7, 30, 60 and 90 days of cold storage. Sensory characteristics of the samples were assessed through Hedonic method. MICs resulted from the test for S. aureus, E. coli, C. albicans and A. niger were 0.1%, 0.065%, 0.03% and 0.01% (V/V), respectively. The results of microbial examinations indicated that with the increasing of the concentration of clove oil essence and also with the progression of storage time, the microbial load was gradually decreased. According to the sensory assays conducted by the consumers, low concentrations of 0.0015% and maximum of 0.01% were found desirable.

Freshwater aquaculture especially hydrothermal fish is increased in recent years. In Chinese carp aquaculture, common carp (CyprinusCarpio)comprises the 15-20 percent of the aquaculture system. Foods obtained from farmed carps could be turn into value-added and ready to eat products such as sausages, salami, burgers and etc. Surimi is one of the intermediate products to make ready to eat foods. Texture properties of surimi products depend mainly on its gelation ability. Through basic preparation of fish paste (setting) for last cooking it would be possible to produce stronger gels. In this research the effect of high and low temperature setting on gelation characteristics of farmed common carp surimi wasinvestigated. For this end, control, kamaboko and suwari treatments were considered. Suwari and kamaboko gels were located at 35°C for 1 hour followed by storage at 4 °C for 12 hours. After setting the suwari gels were cooled,however kamaboko gels were cooked prior to cooling.All samples were examined for water holding capacity, protein solubility, soluble peptides, gel electrophoresis (SDS-PAGE), puncture test and color evaluation. According to the results the lowest rate of whiteness and L* indices were observed in control group. Set gels at 35 °C demonstrated the highest strength, water holding capacity and soluble peptides in TCA and also had the lowest protein solubility and molecule weight of myosin. The results showed that set gels in high temperature results in better physicochemical properties than the gels set at low temperature.

Vacuum packaging is one of the appropriate methods in packaging and storage of fish products. In this study, chemical changes including pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVN) and microbial counts such as coliform bacteria, fecal coliform, salmonella and Escherichia coli in vacuum packed fillet of silver carp (Hypophthalmichthys molitrix) was performed during 30 days storage at 4 ± 1 °C. Fresh silver carp fish samples (ranged 900 to 1200 g) were obtained and transported to the laboratory. Data were analyzed using SPSS 18 software. Results showed that the highest levels of TVN and pH were determined as 63.33 ± 1.82 mg/100 g and 6.81 ± 0.04 in the day 30, respectively. According to the results, TBA, TVN and pH values were increased during 30 days storage. Moreover, total bacterial count increased during the 30 days of storage. Results revealed that coliform counts were less than 2 log cfu/g during the 30 days of storage. Increasing trend of faecal coliform at the end of storage period was estimated as 2.38±0.01 log cfu/g. Considering the microbial populations and the chemical spoilage indicators (TBA and TVN), the shelf life of 15 days was established for the vacuum packaged fillet stored at 4±1°C.