نشریه بهداشت مواد غذایی
سال پنجم شماره 3 (پیاپی 19، پاییز 1394)

Biogenic amines are small organic molecules with an aromatic and hydrocyclic structure. These compounds are formed duo to the decarboxylation of foods’ free amino acids by microbial enzymes. The aim of present study was to investigate the possibility of using putrescine and histamine contents as an indicator to assess the freshness of rainbow trout (Oncorhynchus mykiss). Therefore, using HPLC the concentrations of putrescine and histamine was determined in cold-stored rainbow trout samples. The samples were analysed every 3 days from day 0 to 18. Based on results, histamine was not detected at the first and third days of the storage, however putrescine was estimated at 1.30±0.03 µg/g. Initial concentrations of histamine and putrescine were 0.7 and 1.2 µg/g respectively. Theses parameters reached to 13.5 and 18 mg/g at the end of 18 days of storage which was statistically significant (p<0.05). Moreover, a direct and significant relationship was observed between the load of aerobic mesophilic bacteria and histamine contents in the fish samples. Similar relation (p<0.05) was found between the load of psychrotrophic bacteria and putrescine content. Consequently, histamine and putrescine concentrations could be used as an indicator to assess the freshness of rainbow trout.

This study aimed to assess the occurrence and diversity of mold species in raw milk and its products along with the identification of potential contamination sources. For this reason, a total of 260 samples consisting of 80 raw milk, 100 dairy products (i.e., pasteurized milk, yoghurt, cheese and buttermilk) and 80 environmental (i.e. ingredients, packaging materials, surface of processing equipments and air) specimens were collected. Using culture assay and microscopic observation, the occurrence as well as the diversity of mold species was investigated. According to the results, 82.3% of the samples were identified as positive for mold contamination. The percentage of mold contamination for raw milk was estimated as 97.5%. In the case of pasteurized milk, yoghurt, buttermilk, cheese and environmental samples, it was determined as 52%, 76%, 52%, 56% and 96.25%, respectively. Mold diversity among various samples consisted of Aspergillus, Geotrichum, Penicillium, Mucor, Alternaria, Rhizopus, Stemphylium, Cladosporium, and Fusarium. Results revealed a significant (p < 0.01) correlation between kind of mold species isolated from raw milk and dairy products. Similarly, a correlation was observed between dairy products and environmental sources. Regarding the high occurrence of mold contamination in raw milk and environmental sources, it seems that in some instances heat treatment was not effective enough to inactivate all molds; whereas in some other cases, cross contamination may have resulted in mold contamination. Therefore, it is crucial to maintain hygienic conditions during raw milk handling as well as processing steps. These practices could efficiently reduce the occurrence of mold contaminations in dairy products.

This study was carried out to investigate the accumulation of Pb and Cd in tissue of leek (Allium ampeloprasum persicum) and peppermint (Mentha piperita) treated with municipal sewage sludge of Qods town’s treatment plant, Tehran. For this purpose, after soil preparation, sampling of sewage sludge and assessment of the physicochemical properties of the samples, leek and peppermint plants were divided as treatment and control groups. Afterwards, using ICP-OES the concentrations of Pb and Cd were determined in the tissues of peppermint and leek. Results showed that the concentration (mean ± SD) of Pb in the control and treatment groups was 0.26±0.08 and 0.55±0.16 mg/kg, respectively. Pb concentration in peppermint samples was estimated as 0.26±0.06 and 2.41±0.79 mg/kg for control and treatment group, respectively. Moreover, the mean concentration of Cd in control and treatment groups of leek was 0.083±0.003 and 0.26±0.05 mg/kg and for peppermint 0.057±0.002 and 0.14±0.02 mg/kg, respectively. Comparative evaluation of the evaluated treatments showed that except for Cd in leek and peppermint treatment samples, the mean concentrations of Pb and Cd in both vegetables were significantly lower than EPA permissible limits for human consumption. The results of this study indicated that for reducing the health risks of long-term use of sewage sludge as fertilizer, further monitoring should be performed.

Patulin is a mycotoxin produced by a variey of mold species. In this study, a total of 70 samples consisting of 35 apple leathers and 35 apple juice samples was randomly obtained from different supermarkets of Shahrekord. Using HPLC-DAD technique and in accordance with the Iranian National Standard method, the samples were analyzed for patulin contamination. According to the results, patulin was detected in 14 (40%) of apple leather and 7 (20%) of the apple juice samples. Mean values of patulin concentrations in the apple leathert and apple juice samples were estimated as 34.9± 26.3 and 26 ± 19.7 µ/kg, respectively. Although the mean concentration of patulin was lower than the Iranian/European approved limit (50 µg/kg), patulin contamination level was found higher than the maximum approved limit in 5.7% and 2.9% of the the apple leather and apple juices samples, respectively. Therefore, to minimize the contamination of patulin in theses products, the necessary practices should be conducted.

Staphylococcus aureus is considered as a major foodborne pathogen worldwide which can contaminate milk either through mastitis or unsuitable processing conditions. The aim of this study was to determine the prevalence of S. aureus in raw milk of Saqez as well as to assess the antibiotic susceptibility profiles of the isolates. For this reason, 100 raw milk samples were obtained across Saqez. Presence of S. aureus was determined using conventional culture method; moreover, the antibiotic resistance pattern of the isolates was studied by disc diffusion method. Results indicated that 51 samples were contaminated by S. aureus. Amongst, 19 (37.25%) were resistant to at least 1 antibiotic, 19 (37.25%) to 2 antibiotics, 3 (5.88%) to 3 antibiotics, 5 (9.80%) to 4 antibiotics, 3 (5.88%) to 5 antibiotics, 1 (1.98%) to 6 antibiotic and 1 (1.98%) isolate was found resistant to 8 antibiotics. Results revealed a high prevalence rate of S. aureus in raw milks and also the board antibiotic resistance of the isolates.

In this study, 62 raisin samples including Golden, Green, Teifi and Poloei varieties were purchased from Kashmar, Khalilabad, Bardaskan, Quchan and Shirvan citiy of Khorasan-Razavi province. The sulfur dioxide residue, moisture content, water activity, pH values and total titratable acidity were determined in the samples. According to results, the mean quantity of sulfite residue of Teifi samples of Kashmar, Bardaskan and Khalilabad were 932, 1884 and 2230 mg/kg, respectively. These data for Green variety of the same cities was 1176, 1009 and 658 mg/kg, and for Golden variety were 1226, 2076 and 2484 mg/kg, respectively. In Quchan and Shirvan areas, the mean quantity of sulfite residue of Poloei variety was 1070 and 186 mg/kg, respectively. Among different raisin varieties, the samples collected from Kashmar, Bardaskan and Khalilabad, the Golden samples contained the highest amount of sulfite-residue; moreover, the amount of sulfite-residue in Shirvan’s Poloei sample was higher than Quchan’s. Shirvan Poloei variety showed the lowest pH (3.70) meanwhile, Guchan Poloei variety had the highest (4.05) pH. Golden variety of Khalilabad and Poloei variety of Shirvan had the highest (1.56%) and the lowest (0.8%) acidity, respectively. The highest (12.31%) and lowest (9.66%) moisture content was found in Golden and Teifi varieties of Kashmar, respectively. The highest (0.44) and lowest (0.40) aw value was observed in Poloei variety of Guchan and Teifi variety of Bardaskan. Considering the raisins characteristics, most of the samples were not in accordance with the national/codex standard due to the traditional method of production.

Among the various fungal strains screened for citric acid production, Aspergillus niger is known to produce considerable amounts of citric acid and other organic acids when cultivated in submerge fermentation. In this study, optimization of the medium components was carried out using "one-factor-at-a-time" and response surface methods (RSM). One-factor-at-a-time indicated that the amount of citric acid production was increased along with the increasing of agitation speed (from 150 to 200 rpm), raising the incubation temperature (from 17 to 32) and decreasing pH value (to 2). Moreover, in comparison with the other groups, citric acid production in the treatment containing soy bean powder and minerals revealed a significant increase (up to 25 g/l). The results showed that application of ultrasonic wave during the growth phase could remarkably enhance the production of citric acid. Based on the results of one-factor-at-a-time, sucrose and soy bean powder were the selected additives to test their effect on citric acid production using RSM. The two variables were identified to have significant effects on citric acid production and the maximum citric acid production of 58 g/l was resulted from the combination of 230.87 g/l sucrose and 200.81 g/l soy bean powder. In this study, the significant increase in the production of citric acid in the optimal conditions indicated the using of appropriate statistical methods and also the correct levels of selected variables.

Knowledge about phenotypic features of Staphylococcus aureus isolated from milk and their products is very limited in Tabriz region. The aim of this study was to determine the biotypes of S. aureus. For this purpose, 48 S. aureus strains which were previously isolated from cow raw milk (24), traditional cheese (12) and ice cream (12) in Tabriz region were considered. Biotyping was carried out by means of Staphylokinase production, β-hemolysis, coagulation of cow plasma and crystal violates reaction. Among 48 isolates, 23 and 2 strains were belonged to the human and ovine ecovars, respectively. The rest of the isolates were identified as non-host specific ecovars. Regarding the high prevalence rate of human ecovars in this study, it seems that these ecovars may have been transmitted to these products via human handling.