نشریه بهداشت مواد غذایی
سال چهارم شماره 1 (پیاپی 13، بهار 1393)

Mycobacterium avium subsp. paratuberculosis is the etiological agent for Johne’s disease which is known as chronic disease in cattle and may attribute to Crohn’s disease in human. High prevalence of Mycobacterium avium subsp. paratuberculosis has been reported in dairy cattle worldwide. Recognition of infected animals is a major factor to control the spread of the organism. In this regard, detection of the bacterium in milk of clinically suspicious and apparently healthy cows is the best way to control the infection. Although isolation of Mycobacterium avium subsp. paratuberculosis by culture assay is considered as the gold standard, PCR method helps us to recognize the occurrence of slow-growing microorganisms in a short period of time with high sensitivity. In this survey, a total number of 160 cow milk was sampled and cream layer together with the pellet of each sample was tested by PCR and culture technique. Using Kappa statistics it was revealed an almost perfect agreement between culture and PCR assay with a product size of 400 bp; however, the agreement between culture and PCR with product size of 228 bp was found substantial. Results showed a substantial agreement between PCR with product sizes of 400 bp and 228 bp. Comparing the agreement between the two PCR approaches with culture assay as gold standard test, it was assumed that PCR could be a robust and rapid method to detect Mycobacterium avium subsp. paratuberculosis in milk. Consequently, PCR can be introduced as a screening test for detection of the bacterium in cow milk.

In numerous studies the beneficial impacts of probiotics on human health have been documented. Hence, there is a strong trend for the production of such foods and dairy products in particular, by many of the food processing establishments. In this regard, one of the major perequisites is to recognize the optimum conditions affecting the growth of probiotic organisms. This study aimed to investigate the impact of various concentrations of dextrose, valine, glycine and thiamine as well as different incubation temperatures on growth rate of Lactobacillus acidophillus in steril milk. In order to locate the ideal temperature, L. acidophillus was incubated at 38 °C, 40 °C, 42 °C and 44 °C. Moreover, thiamine (0, 5, 10 and 15 ppm), dextrose (0, 0.4, 0.6, 0.8 and 1%), glycine and valine (0, 30, 60, 90 and 120 ppm) was added to steril milk. The acidity of milk-as an indication of bacterial activity-was measured periodically during 0, 1, 2, 3, 4 and 5 h of incubation. In comparison with the other temperatures, the activity of L. acidophillus was found significantly (P < 0.05) higher at 42 °C. According to the results, addition of dextrose, valine, glycine did not accelerate the production of acidic components; however, it seems that these substances could enhance the potency of L. acidophillus to produce gas and proteolytic enzymes.

Consolidated fish burger is a new product which is a combination of common Kilka (Clupeonella cultriventriscaspia) and Silver carp (Hypophthalmichthys molitrix) minced with flavors, fillers, vegetables and tofu dressing. Consolidated fish burger is produced in order to boost the nutritional value and to reduce the cost of end product. This study aimed to investigate the variations in the composition of consolidated burger during 4 months of storage at -18 °C. For this purpose, 4 types of burgers with a combination of a various percentages of Kilka and Silver carp were produced. The chemical composition by means of total protein, fat, moisture and ash contents were evaluated during preparation (zero phase) and 4 months of storage. Results showed that at zero-phase protein% and moisture% in raw Silver carp was higher, whereas fat% and ash% in Kilka was found higher. Protein content in all groups was decreased during 4 months of storage. The decreasing rate was more rapid in control group as well as treatment 3. Fat percentage was dropped during the storage period and the decreasing trend in treatment 2 was found higher. In the case of moisture, the percentage was declined in all groups and in treatment 1, in particular. Considering the results, it was concluded that freezing could significantly decrease the nutritional value of the consolidated Burgers.

In present research, the fish cake was produced from Big-Head Carp Artichthys nobilis based three formulations and according to organoleptic tests best formula was chosen including 65% of fish flesh. Then, the selected product was packed in polyethylene coverage and frozen at -18˚C. For determining biochemical compositions (including nutrient compounds and fatty acids profile) and qualitative parameters (such as TVN, PV & TBA), the microbial counting (Total Count of bacteria and Psychrophilic) were carried out in specific time intervals 0, 30, 60 and 90 days. The results showed that in the samples from day 0 up to 90, amounts of TVN were reached 11.97±0.06 to 16.82±0.62 mg/100, PV from 1.13±0.05 to 0.54±0.06 meqO2/kg and TBA from 0.51±0.01 to 0.74±0.05 mgMDA/kg. The results of bacteria counting showed that total count decreased to 3.20 ± 0.17 due to freezing from 3.52±0.02 logcfu/g and psychrophilic count Initially increased and then decreasedfrom 3.52±0.02 to 3.29±0.01 logcfu/g at last day which both were in acceptable range (p<0.05). On the other side, the unsaturated fatty acids (UFA) were decreased from 76.97 to 73.38% (p<0.05) after 90 days of freezing. The final conclusion demonstrated that produced fish cake from Big-Head Crap including 65% fish flesh had an acceptable chemicals, qualitative indexes and Microbal count during 90 days of freezer storing.

Salmonella typhimurium and S. enteritidis are known as the major causes of food-borne infection throughout the world. The present study was carried out to investigate the prevalence of S. typhimurium in raw milks of Chahamaha Va Bakhteyari province. For this reason, a total of 550 raw milks (consisting of 200 cow, 175 sheep and 175 goat milk samples) were collected through October 2011 to March 2012 from dairy herds around Shahrekord. The samples were cultured and the isolated colonies were confirmed by PCR using species-specific ST11 and ST15 primers. According to the results, a total of 20 samples (3.63%) were found positive for Salmonella spp. Amongst, 14 (2.54%) of cow milk, 2 (0.36%) of sheep milk and 4 (0.72%) of goat milk samples were contaminated. Using PCR, 9 (1.63%) samples were contaminated with S. typhimurium. The results indicated a relatively high occurrence of S. typhimurium in raw milks. Therefore, it is essential to maintain hygienic measures during milking and handling. Besides, it is recommended not to use raw milk for the manufacturing of dairy products such as cheese and ice-cream.

Nowadays, the existence of aluminum in human diet as a food contaminant has attracted the concerns of many researchers. It seems that the cooking pans are common sources of aluminum exposure through foodstuffs in Iran. The aim of this study was to evaluate the migration of aluminum from cooking containers into foodstuffs. For this purpose, solutions with different concentrations of citric acid, sodium chloride, fat, protein and sugar were prepared and migration of aluminum into these solutions was measured using atomic absorption spectrometry. Results showed that salt and citric acid concentrations could enhance aluminum migration; whereas, acid concentration was more effective than salt due to its corrosive effect. The intensity of heat processing and the duration of heat treatment had direct relation with aluminum migration. The aluminum content of cooked foods in aluminum cooking pans was also significantly more than control samples.

Nowadays, the demand for bottled water is spiked in most countries including in Iran. Monitoring the microbial and chemical quality of bottled water is essential to guarantee the consumers’ health. The present study was aimed to examine the microbial and chemical quality of bottled water distributed in Hamedan province. For this reason during winter and summer of 2012, a total of 56 samples was collected randomly across the province. Analysis were carried out based on standard methods on chemical parameters such as pH, alkalinity, nitrate, sodium, potassium, fluoride, sulfate, phosphate, total hardness, permanent hardness as well as microbial quality of fecal coliform and total coliform. The data was analyzed by SPSS software and compared with Standard Methods of Iran and WHO. No total and fecal coliforms were detected in all samples. pH, alkalinity, nitrate, sulfate, phosphate, sodium and potassium values in all samples were in the range of approved by the Iranian Standards. Among the 56 samples, fluoride concentration in 44 samples was lower than desired maximum standard level and in 40 samples total hardness was lower than approved maximum standard limit. Although in most of the samples the mean value of the parameters were in the approved limit adopted by the Iranian and WHO regulations; however, a significant difference was observed between the measured parameters and their labeling quantity provided by the manufacture. Results revealed no significant difference between the mean value of the measured parameters obtained during winter and summer.

The aim of this study was to develop a species-specific PCR method for rapid identification of meat species in order to detect any potential fraud in meat products. For cattle and poultry, a set of primers were designed based on the mitochondrial cytochrome b and subsequently a 183 bp as well as 274 bp fragments were amplified for poultry and beef samples, respectively. For the study, ten different brands of beef sausage were obtained across Tehran province. Results of PCR assay demonstrated that unlike their labels, all of the samples were contained poultry residuals. Moreover, beef offal was detected only in five samples. Since no cross-reaction was observed among the different samples, PCR could be considered as a sensitive and specific method for the identification of meat varieties. In addition, high-speed operation and easiness of the technique are the other advantages of PCR method. Therefore, this technique has the capability for sensitive and specific detection of meat adulteration in sausages.