JOURNAL OF FOOD HYGIENE
Year:2012 | Volume:1 | Issue:4 (4)|Papers Count:8

Salting of fish is a traditional method for fish preservation which reduces corruption, increase shelf life and is used in order to have an access to the new markets. In some countries, consuming semi-cooked or raw salted and smoked fish is well-liked. Due to the presence of halophilic microorganisms in salted fish, occurrence of food-borne infections is probable. The aim of this study was to investigate the antimicrobial activity of NaCl on Staphlococcus aureus and Listeria monocytogenes in salted silver carp. Effect of different concentrations of NaCl (4, 8, 12%) on behavior of Staphlococcus aureus and Listeria monocytogenes in 10oC during 3 weeks (0, 1, 2, 3, 6, 9, 12, 15, 18, 21 days) was determined by evaluation of the bacterial growth in salted fish fillets. Statistical analysis showed that application of different concentrations of NaCl had significant inhibitory effect on the growth of S. aureus and L.monocytogenes in salted fish fillets compared to control group (p<0.05). This study indicated that application of NaCl without any complementary element is not considered as a good preservative for extending the salted fish shelf-life. Consequently using of other natural preservatives along with salting is suggested.

The aim of present study, was to scale up the production of L (+) lactic acid from the laboratory to pilot plant using Lactobacillus casei subsp. casei PTCC 1608. Moreover, the minimum inhibitory concentration of the produced lactic acid and sodium lactate against 4 test strains including Staphylococcus aureus PTCC 1113, Microccoccus luteus PTTC 1110, Escherichia coli PTCC 1330 and Listeria monocytogenes PTCC 1304 were evaluated. According to the results, the specific growth rate of each test strain was decreased by lactic acid. The inhibitory effect of the sodium lactate was lower than lactic acid in all of the experiments. The best carbon (glucose, lactose and whey) and nitrogen (corn steep powder) sources were optimized in batch and fed batch system and also pH, temperature and aeration were improved in shake flask incubator, 20 l and 750 l stirred tank reactors (STR). Glucose (80 g/l) supplemented with (50 g/l) whey was found as the best production medium. Productivity and yield of calcium lactate production in laboratory scale were 0.51 g/lh and 0.56%, respectively. Fed batch production of calcium lactate in 20 l bioreactor increased the productivity and yield up to 2.47 and 0.83%. Production and productivity was increased up to 350 g/l and 5.4 g/lh, respectively in scaled up processes by 750 liters bioreactor (STR).

In order to investigate the presence of virulent Yersinia enterocolitica in pasteurized milk, 242 samples were collected from Tabriz retails from 2011 to 2012. The samples were enriched in PSBB. Afterwards, virF and ail genes were exploited as target sequences for the detection of virulent Y. enterocolitica. PCR-positive samples were cultured on CIN agar and MacConkey agar. The selected isolates were confirmed by second-phase duplex PCR. For the biotyping of Y. enterocolitica, certain biochemical tests were performed on the isolate. The pasteurized milk samples were further analyzed for the enumeration of hygiene indicator bacteria and qualitative alkaline phosphatase (ALP) test. Virulent Y. enterocolitica were detected in 6.61% (16/242) of samples by ail-PCR, however, using virF-PCR 4.13% (10/242) of the samples were identified as positive. Among PCR-positive samples only 0.41% (1/242) were isolated by culture method and confirmed by second-phase duplex-PCR. Based on the biochemical assays, the isolated Y. enterocolitica was identified as biotype 4. Furthermore, 11.57% (28/242) of the samples were found positive for alkaline phosphatase test. The results revealed that the number of hygiene indicator bacteria in ALP-positive samples was significantly (p<0.01) higher than ALP-negative samples. Since Y. enterocolitica is very susceptible to pasteurization process, cross contamination could be the main reason for the presence of virulent Y. enterocolitica in the pasteurized milk.

Consumption of large amounts of fruits and vegetables throughout the world, have encouraged the development of various methods for their processing. Drying is considers as the most common method for preservation of vegetable and fruits. Although drying extend the shelf-life, it has various side effects on keeping quality of these foods; including decreasing of the color and texture quality as well as missing the flavor and nutritional values. These negative effects have increased the demand for the discovering the alternative drying methods and consequently for the production of fresh-like products. The aim of this study was to introduce and optimize the novel method for the drying of carrot as well as to develop and optimize the quality of osmo-air-dried carrots with special respect to the color, flavor, texture, rehydration properties, density and shriveling of the product. For this, the effect of osmotic pretreatment on the density of carrot slices was investigated, using 50% glucose syrup +5% salt at 40oC with 150 rpm, followed by complementary drying step. The result of treated group was compared with control samples which were dried only by hot-air-drier. The results showed that using osmotic pretreatment could increase the density through inhibition of the product’s shrinkage. Meanwhile, in air-dried samples the density was decreased considerably and high shrinkage was also observed.

Mycobacterium avium paratuberculosis is the causative agent of John’s disease which is a remedial chronic disease in all ruminants and is important from economical viewpoint. In this study, a total of 86 fecal samples from suspected dairy cattle were obtained from 11 traditional dairy farms in Moghan region. All samples were evaluated by direct microscopic examination. Subsequently, milk sample of the related cattle were tested by PCR technique. Twenty samples from positive and 10 specimens of negative samples in direct microscopic assay were selected randomly for PCR examination. Among the 86 samples, 51 (59%) samples were positive, while, 35 (41%) samples were found as negative by microscopic assay. From 20 positive samples, 19 (95%) samples showed positive result by PCR, however, among negative samples, 3 (30%) samples were positive in PCR assay. Results revealed that there is a direct relation between contamination of fecal and milk samples. Moreover, due to the correlation between the results of microscopic examination of fecal samples and PCR assay of milk specimens, direct microscopic evaluation of feces could be performed prior to PCR-based detection of Mycobacterium avium paratuberculosis in milk samples. According to the results, high contamination rate of Mycobacterium avium paratuberculosis was found in milk samples. On the other hand, duo to possible etiological role of this bacterium in the development of Crohn’s diseases in human, it should be considered as a serious concern indeed.

Aflatoxin M1 (AFM1) appears in milk as a direct result of the ingestion of feed contaminated with aflatoxin B1 by cattle. This study was conducted to investigate the contamination rate of raw milk whit aflatoxin M1 in Chaloos and Ramsar raw milk collection centers. Two hundred bulk raw milk samples were collected during winter (January and February) and summer (June and July) seasons. The milk samples were analyzed by ELISA method for the presence of AFM1. During the winter, AFM1 was detected in 100% and 59.79% of the bulk raw milk samples in Ramsar and Chaloos, respectively; however, during summer 83.52% and 50.1 of the samples was found as positive in Ramsar and Chaloos, respectively. Furthermore, 45% of Ramsar and 30% of Chaloos bulk milk samples showed higher contamination level of AFM1 than maximum tolerance limit (50 ng/l) accepted by National Standard as well as European Union. Although, the difference between the contamination rate in samples obtained during summer and winter seasons was not statistically significantly, (p<0.05) significant difference (p<0.05) was observed between Chaloos and Ramsar samples in each season. Moreover, highest contamination rate was found in February.

Campylobacter jejuni/coli are frequent causes of diarrhea in humans worldwide originating in foods of animal origin mainly from meat. The aim of this study was to determine the prevalence of Campylobacter spp. in lamb at different stages of the slaughter line including: after-skinning, after evisceration and the end of slaughter process. A total of 150 lamb samples (50 samples per each stage) were collected over a period of 16-month between January 2006 and May 2008, and were analyzed for the presence of Campylobacter spp. According to the results, Campylobacter spp. were isolated from 11.3% (17/150) of the carcasses from the three sampling stages. Among the isolates, 76.5% were identified as C. jejuni and 23.1% as C. coli. Campylobacter spp. were isolated from 5%, 8% and 4% of carcasses during the stages of after-skinning, after-evisceration and the end of slaughter process, respectively. Antibiotics susceptibility of 17 isolates were determined for ten different antibiotics using the disk diffusion assay. Results revealed that 58.8% of the isolates were resistant to ciprofloxacin, while 47.1% of the isolates to nalidixic acid, 41.2% to tetracycline, 29.4% to enrofloxacin, 23.5% to ampicillin, 5.9% to amoxicillin, and 5.9% top streptomycine. None of the isolates was resistant to erythromycin, chloramphenicol and gentamicine. This study emphasizes the application of a preventive system such as HACCP (Hazard Analysis of Critical Control Points) for the control of Campylobacter contamination in slaughterhouse.

Brucellosis is a zoonotic disease caused by gram-negative bacteria Brucella that are pathogenic for a wide variety of animals and human beings. Brucellosis, in particular, is easily transmitted via raw milk. Despite its control in many countries, it remains endemic in Iran. The transmission of brucella from infected animals to humans occurs either by occupational contact or the consumption of contaminated animal products, especially milk, cream and fresh cheese. The purpose of this study was to evaluate the prevalence of cow raw milk contamination by Brucella abortus in Parsabad region. A total of 64 cow’s raw milk samples were collected using cluster random sampling method from Parsabad milk collection centers from March to April 2009. Samples were monitored for Brucella abortus antibodies using Milk Ring Test. Based on the results of this study, the occurrence of Brucella abortus was estimated as 37.5% in Parsabad region. It was concluded that the presence of Brucella abortus in bulk raw milks of Parsabad region is very probable. Therefore, it is necessary to determine the prevalence of Brucella abortus in bulk raw milks using the microbiological assays.