فصلنامه علوم تغذیه و صنایع غذایی ایران
سال چهارم شماره 4 (پیاپی 15، زمستان1388)

The two main methods for obtaining microbial strains with specific characteristics for application in the industry are isolation from natural sources and using random mutagenesis. Characterization of all isolated strains is very time-consuming and expensive. In this study the tolerance of some strains of Saccharomyces cerevisiae to different stresses was measured and the association between these stresses and tolerance to osmotic pressure and production of intracellular trehalose determined, aiming at applying the results to designing selection media. The viability (percent cell survival) of different strains of Saccharomyces cerevisiae was assessed by exposure to a 3M Nacl solution, a 40% sorbitol solution, a freezing shock at -20º C, and a heat shock at 52º C. In addition, the intracellular accumulation of trehalose was determined by the antrone reagent. The associations between these factors and resistance of Saccharomyces cerevisiae strains were then determined using statistical tests. Strong correlations were observed between resistance to NaCl- and sorbitol-introduced stress and strains of Saccharomyces cerevisiae (p<0.01). There was also a strong association between intracellular trehalose accumulation and resistance to heat shock (p<0.01). While sugars can not select osmotolerant cells, Nacl is a very strong selector for more specific isolation of more resistant cells in a suspension. Similarly, heat shock stress is very efficient in selecting cells with a higher intracellular trehalose accumulation in a suspension.

Outcomes of diabetes mellitus play an essential role in the pathogenesis of atherosclerosis and its complications. Persons with type 2 diabetes mellitus have lower plasma vitamins E and C levels. Lower levels of these vitamins may increase the risk of oxidative stress. In this study we assessed the effects of omega-3 fatty acids plus vitamin E and vitamin C plus zinc supplementations on glycemic control in postmenopausal women with type 2 diabetes, compared with a control group. In this 12-week double-blind placebo-controlled clinical trial, 75 postmenopausal women with type 2 diabetes from among those consulting the Iranian Diabetes Association, Tehran, participated. The subjects were randomly assigned to one of three groups, to take, daily for 12 weeks, 1.8 g omega-3 fatty acids plus 400 mg vitamin E (group 1), 5 mg zinc plus 300 mg vitamin C (group 2), or a placebo (group 3). Analysis of variance and repeated measure analysis of variance were used for inter-group comparisons and the changes in the three groups and adjustment of the other variables, respectively. At baseline, there were no significant differences in glycemic parameters among the three groups. Changes in HOMA-IR in group 1 were significantly higher than those in group 2 and the placebo group (-0.9±0.6 vs. 0.9±0.5 and 0.4±0.4, respectively) (p=0.012). After intervention, changes in fasting plasma insulin (-1.6±1.3 vs. 0.6±0.8 and 1.6±0.7 mU/l, respectively) (p=0.038) were higher in group 1, while they were lower in the other 2 groups. The supplementation caused a significant decrease in the mean changes in fasting plasma glucose in group 1 and a significant increase in group 2 (-11.1±14.1 vs. 27.9±10.9 mg/dl, respectively)(p= 0.039). Simultaneous reductions in HOMA-IR and plasma insulin as the most important cardiovascular risk factors in group 1 taking daily 1.8 g omega-3 fatty acids plus 400 mg vitamin E is encouraging, because it can have practical clinical implications. Duration of diabetes may have influenced effectiveness of the treatments.

Kefir is one of the oldest traditional beverages produced by lactic-alcoholic fermentation of milk. On the other hand, milk whey, a by-product of the cheese-making industry, has high contents of valuables nutrients. However, it is usually discarded in Iran, which causes contamination of the environment around the milk processing plants, specially surface and underground waters. Whey fermentation by isolated kefir starter cultures could be a sensible solution towards solving this problem. In the present study, various ratios of starter culture of kefir grain were used for production of a fermented beverage using whey as the substrate. Acidic whey was used to produce a fermented beverage. Culture media were prepared using various ratios of lactic acid bacteria, yeasts, and acetic acid bacteria isolated from kefir strains and used in the production of the beverage. Keeping constant the incubation time (24 h) and temperature (25ºC), substrate (pasteurized whey), inoculation rate (3% – 5%), and mixing rate (90 rpm), samples of the beverage with various ratios of the cultures were produced and analyzed for sugar, fat, protein, riboflavin, alcohol, carbon dioxide, dry material and ash. Three different essences, namely, those of Mentha paprika, Anethum graveolens, and Thymus vulgaris were added to the beverage samples, which were then tested for organoleptic properties. Beverage samples were produced using an inoculation rate of 3% individual starter cultures and mixed cultures of Lactobacilli, Coccci, and yeasts. After finding the best ratio in each case, inoculation rates of 3% and 5% were used. Based on organoleptic and chemical (acidity and carbon dioxide) properties, out of the 61samples produced 8 were judged to be desirable. Based on the results it can be concluded that, with regard to color, flavor and aroma, the beverage with Mentha paprika essence is the most desirable. Also, results showed that beverage samples produced with 3% (v/v) lactic acid and acetic acid bacteria and 2% yeast culture (v/v) were the best with respect to quality and acceptability.

Diabetic nephropathy is the most common cause of kidney failure. High serum concentrations of advanced glycated end products, oxidative stress, and hypertension are three important risk factors for diabetic nephropathy. As individual administration of lipoic acid or pyridoxine is not effective in improving diabetic nephropathy, the present study was designed to investigate the effects of combined administration of lipoic acid and pyridoxine on albuminuria, oxidative stress, blood pressure, serum advanced glycated end products, nitric oxide and endothelin-1 in patients with diabetic nephropathy. The study was a double-blind randomized clinical trial, in which 38 patients with diabetic nephropathy (23 females and 15 males) were randomly assigned to either a supplement-taking group or a placebo group. The patients in the supplement group received 800 mg lipoic acid and 80 mg pyridoxine daily for 12 weeks, while the placebo group received placebos. At baseline and at the end of week 12, a urine sample and 8 ml blood were collected from each patient after a 12- to 14-hour fast and serum pentosidine, carboxymethyl lysine, malondialdehyde, endothelin-1, nitric oxide, glucose, urinary albumin, systolic and diastolic blood pressures were measured. The serum concentrations of pentosidine and carboxymethyl lysine decreased significantly in the supplement-taking group at the end of week 12 as compared to the baseline values (P<0.05). The combined supplement also brought about significant reductions in the serum malondialdehyde (25%), systolic blood pressure (2 mmHg) and urinary albumin concentration (74 mg/g creatinine); the reductions were significantly different from the placebo group values (P<0.05). On the other hand, the serum nitric oxide concentration increased significantly in the supplement-taking group as compared to the placebo group (P<0.05). No significant differences were observed between the two groups in the mean changes of serum endothelin-1, glucose or diastolic blood pressure. The results indicate that combined administration of lipoic acid and pyridoxine reduces significantly serum pentosidine, carboxymethyl lysine, malondialdehyde, systolic blood pressure and urinary albumin concentration, and increases serum nitric oxide. This treatment may, thus, have an effective role in retarding the progression of diabetic nephropathy.

Due to their nutritional, physical and chemical characteristics, mycoproteins, produced in the process of fungal growth, have been proposed to be used as a food additive for man. In this study a central composite design was applied to assessing the effect of seed size and initial concentrations of carbon and nitrogen sources on mycoprotein production by Fusarium venenatum (ATCC20334) from date sugar. Chemical composition (percent dried cell weight, nitrogen, moisture, and ash) and pH of the substrate were determined. Vogel culture medium was used for maintenance and inoculum preparation, and incubation was done at 30 °C for 72h. Dried cell weight was measured by the oven method. The experimental results were fitted to a full quadratic second order polynomial equation and the optimization of response was done with Minitab 14 software. Optimum conditions were determined and a confirmation test was conducted. The regression coefficient of the model presented for mycoprotein production (based on dried cell weight) was 98.0%. The optimum conditions for the mycoprotein production included a seed size of 15.39 % v/v, and a carbon and nitrogen source of 20 and 4.35 g/L, respectively. The predicted value for the optimum production of dried biomass was 5.032 g/L. The reconfirmation test was conducted at the optimum conditions and the result obtained was 4.84 g/L of biomass production. The regression coefficient indicates accuracy and suitability of the model for the experimental data. By changing the inoculum conditions and the chemical composition of the culture medium, optimal growth of Fusarium venenatum and, consequently, maximum biomass production, can be achieved. Use of date syrup as an available and domestic Iranian substrate for modification of Vogel medium makes possible protein production at an industrial scale in surface culture.

Food insecurity, as a major public health problem during the past two decades, has received the attention of population experts, scientists and policy-makers. In Iran, based on daily energy intake, 20.0% and 23.2% of households were food-insecure in 1996 and 2001, respectively. Studies have also shown that food insecurity is 99.2% among households under coverage of Imam Khomaini Relief Committee and 36.2% in the Asadabadi Region. So far, food insecurity has not been assessed directly at national, provincial or district levels. This study determined the prevalence of household food insecurity and some associated factors in the urban areas of Shiraz, Iran. Measurement of food insecurity and determining its determinants can help policy-makers in planning, monitoring and evaluating food security promotion program..

In this cross-sectional descriptive-analytical study, 778 households from the urban areas of Shiraz were selected by the multi-stage cluster sampling method. Demographic and socio-economic data were collected using standard questionnaires; household food security was assessed on the basis of the USDA 18-item questionnaire. Factor analysis and the Chi-square test were used for socio- economic status criteria determination and data description, while one-way ANOVA and ordinal and linear logistic regression were used for data analysis and identifying the associated and predictive factors. The software used was SPPS 14.

The prevalence of household food insecurity was 44% (food insecurity without hunger 27.8%, and food insecurity with moderate and severe hunger 14.4 and 1.8, respectively). Food insecurity was greater in female-headed families, those with a larger number of children, or those with children under 18 years old (P=0.05). It was positively associated with socio-economic status (P=0.0001). Based on the final ordinal logistic regression, predicting factors for food insecurity were children under 18 years old in the family)CI95%:1.28-2.34, OR:1.73), low socio-economic status (CI95%:6.36-14.44, OR:9.56), and responder (mothers) (CI95%1.01-2.83, OR:1.7).

Household food insecurity exists in Shiraz. Having children under 18 years old in the family and low socio-economic status are the most important causes of household food insecurity. Policies and programs, such as promotion of socio-economic status, and approaches to promote the situation of under 18-year old children, such as school lunch programs, can help reduce food insecurity.

Thirty percent of agricultural products are annually wasted in Iran, 7 to 8 percent of which are due to improper packaging. In this study, the effects of seven types of nanofilms with low a permeability to oxygen and water vapor on organoleptic and microbial properties of bread were investigated. Voluminous (i.e., non-flat) bread samples packaged in nanofilms were stored at 5°C, 20°C and 35°C and tested for organoleptic properties on days 1, 3, 5, 7, 14, and 21of storage. Also microbial counts in the samples kept at the 3 temperatures were made on day 14. The three main factors affecting significantly staling of the bread samples were type of nanofilm, temperature, and length of storage. The effects of combination of each 2 factors were also statistically significant (p<0.01 and 0.05). The lowest and highest amounts of staling on day 14 occurred in bread packaged in a 3% composite film (500ppm silver and 450ppm clay) and in the control package sample (with no nano-particles), respectively. The total microbial count decreased with increasing silver nano content of the film, such that the 2% (1000ppm) silver film had the lowest count. In addition, the control packaging at the 3 storage temperatures showed the highest counts for coliform and moulds. The lowest and highest counts for coliform and moulds were found in nano-packaging samples kept at 5°C and 35°C, respectively. In conclusion, the nano composite film with 3% nano-particles (SC3) was judged to be the best film due to lower cost and longer conservation of bread freshness.

In type 2 diabetic patients, high fasting and postprandial triglyceride and decreased HDL-C levels are very common, increasing the risk of cardiovascular disease. This problem can be managed by dietary modifications, such as the reduction of saturated fatty acids (SFAs) intake and their substitution with monounsaturated fatty acids (MUFAs) or polyunsaturated fatty acids (PUFAs). This study was conducted to compare the effects of consuming olive and sunflower oils as a substitute for a portion of daily dietary fat on fasting and postprandial blood glucose level and lipid profile in type 2 diabetic female patients. This randomized crossover clinical trial was conducted on 15 postmenopausal women with type 2 diabetes (51.7  1.2 years old). Using a 3day 24-hour dietary recall questionnaire showed that their average daily intake of hydrogenated oil was 16.1±2.3g, 40% of total fat intake. The patients were randomly assigned to one of 2 groups, consuming either olive oil or sunflower oil (substituted for hydrogenated oil) for 3 weeks. After a washout period of 3 weeks, the subjects in each group switched to the other oil for the following 3 weeks. In all cases the subjects took their usual breakfast. Anthropometric measurements were made, physical activity was determined, and biochemical tests (fasting and postprandial blood sugar) were done at the beginning of the study and at the end of weeks 3, 6, and 9. Food intake was measured using the 24-h dietary recall technique and Nutritionist IV software at the same time points. As compared to sunflower oil, olive oil resulted in reductions in fasting blood glucose (p<0.01), triglycerides (p<0.01), postprandial blood triglyceride (p<0.05), and TG/HDL-C (p<0.05). There were no significant changes in anthropometric measurements, physical activity, or dietary intake of the patients during the study. As expected, substitution of hydrogenated fat with the 2 oils resulted in significant increases in the intakes of MUFA and PUFA and decreases in the intake of SFA (P<0.01). Considering the beneficial effects of olive oil on blood glucose and lipid profile, it can be concluded that partial substitution of dietary fat with olive oil, in preference to sunflower oil, can help reduce CVD risk factors in type 2 diabetic patients.