مجله علوم و صنایع غذایی ایران
سال هفتم شماره 2 (پیاپی 24، تابستان 1389)

Mastitis deteriorates the quality of raw milk and higher proteolytic activity in mastitic milk has been reported. There are no published studies on the effects of health status of the animal on the casein micelle microstructure، therefore the specific objective of this study was to determine the effects of somatic cell count (SCC) on the dimension and microstructure of casein micelles in raw milk. Raw milk samples were collected from the individual quarter of the dairy cattle in three different levels of SCCs (i. e.، low: SCC<200،000، medium: 200،000800،000 cells/ml) and prepared for study by Scanning Electron Microscopy (SEM). The results suggested that the size of casein micelle changes in mastitic milk، and there were significant differences in casein micelle microstructure between high and low SCC milk samples. The mean diameter of micelles in medium and high SCC specimen decreases dramatically and SEM micrographs revealed that aggregation of casein micelles increases considerably in raw milk samples، especially in high SCC milk، except for that of low SCC. Increase the activity of proteolytic enzymes such as plasmin and lysosomal enzymes (Elastase، Cathepsin B، D and G، etc) was realized as the main reason of hydrolyzing casein in milk، especially in milk with high SCC، which can be the cause of changes in size and tendency to aggregation of casein micelles in mastitic milk. In addition، decreased milk synthesis ability and reduced steric and electrostatic repulsion among casein micelles might be other causes for this phenomenon.

Keywords: Somatic cell, Raw milk, Scanning electron microscopy, Casein micelle

In order to produce cocoa butter replacer، the hydrogenated (180 °C temperature، 400 rpm mixing rate and 0. 4 percent Ni catalyst) and solid fraction (centrifugation at 10000g for 5-10 min at –20 °C) of tea seed oil، at weight percent ratio of 30:70 was modified by the chemical and enzymatic esterification. The results show that enzymatically esterified sample (EIS) had the melting point and triacylglycerol species closer to those of cocoa butter than chemically interesterified sample. Results also showed that at EIS percentages of 5 and 10، there is less effect on texture of chocolate than other percentages (15 and 20 percent). Based on the results taken from bloom formation and sensory evaluation، adding up to 10 percent of EIS reduces the bloom rate without damaging the sensory attributes in chocolate samples.

Hazelnut is a rich source of energy and contains 40-60% lipid. Because of its high oil content، essential fatty acids، phytosterols، antioxidants and minerals has a high nutritional value. However، phytosterol oxidation products (POPs) may have negative effects on health. In this study، effects of hazelnut oil refining were studied on fatty acid composition، phytosterols، POPs and tocopherols. Fatty acid composition، phytosterols and POPs after separation and enrichment with solid phase extraction (SPE) were analyzed with gas chromatography (GC) and tocopherols determined with high performance liquid chromatography (HPLC). Refining processes had negligible effects on fatty acid composition of analyzed hazelnut oil sample. However، refining processes had noticeable effects on phytosterols، POPs and tocopherols. In the refined oil، total amount of phytosterols، POPs and tocopherols were reduced from 1369. 8 ppm، 10. 57 ppm and 334. 4 ppm to 1061 ppm، 3. 19 ppm and 183 ppm، respectively.

The influence of whole soy flour 0-27%، water content 31-35% and different extrusion condition on the cooking quality of spaghetti in order to production of functional pasta، were evaluated. Process was performed with screw speed of 10-40 rpm and water circulating temperature of 35-70 °C. The results showed that adding whole soy flour caused significant (P≤0. 05) decrease in cooking time، cooking weight characteristic. However، cooking loss of spaghetti increased significantly (P≤0. 05)، when whole soy flour increased in formulation. Temperature and screw speed of extruder had no significant effect alone on the cooking attributes. But، Interaction between water temperature، screw speed and components also had a slight synergistic effect on the characteristics. Also، interaction between components and water temperature has negative effect on the cooking loss. Data analysis using mixture design showed that the cooking characteristics of spaghetti were optimized when 44. 7 % wheat flour، 24. 3 % whole soy flour and 31% water content at screw speed of 25 rpm and temperature of 52. 5oC were applied.

Gluten strength is the major factor affecting mixing characteristics، extensibility، elasticity، and stability of dough. Wheat bug injects a protease enzyme into immature wheat kernels while feeding. This enzyme remains in flour made from bug damaged wheat and، in dough، digests gluten to produce slack، sticky dough and poor quality bread. The effect of sonication conditions on dough rheology affected by protease inactivation in flour made from bug damaged wheat were investigated. Results showed that sonication with 70% amplitude in 5 min maintained rheological properties of dough. Sonication improved water absorbtion، dough stability، extensibility، and resistance to extension. Bread baked from bug damaged flour treated by sonication had better color، texture، specific volume، and appearance.

The probiotic، Lactobacillus acidophilus PTCC 1643 was encapsulated in calcium alginate beads with the objective of enhancing survival during exposure to the adverse conditions of the gastro-intestinal tract. The probitic was incubated in simulated gastro-intestinal conditions for 0، 30، 60، 90 and 120 min. at 37 oC. The survivability of the probiotic، L. acidophilus PTCC 1643 was expressed as the destructive value (D-value). Particle size distribution was measured using laser diffraction technique. bead appearance was observed by scanning electron microscopy (SEM). The alginate coat prevented acid-induced reduction of the probiotic in simulated gastric juice (pH 1. 5، 2 h)، resulting in significantly (P < 0. 05) higher numbers of survivors due to retarding the permeation of the gastric fluid into the cells. After sequential incubation in simulated gastric (60 min) and intestinal juices (pH 7. 25، 2 h)، number of surviving cells were 6. 5 log cfu ml -1 for encapsulated L. acidophilus while 2. 3 log cfu ml -1 was obtained for free cells.

Date wastes، one of the abundantly available carbohydrate agricultural wastes in the South and East of the Mediterranean، were served as a novel substrate for the production of glutamic acid، the precursor of monosodium glutamate. A fractional factorial design was used to investigate the effects of variables، namely biotin content، urea content and agitation speed on the response glutamic acid production. A second order polynomial model was used to predict the response. Agitation speed was found to significantly influence the glutamic acid production. The highest glutamic acid production was recorded at agitation speed ranging 240-250 rpm and urea concentration of 2. 8-3 g/l. The study showed that the wastes from dates could serve as a low-cost substrate for glutamic acid production.

Drying of foods is one of the most important preserving methods due to reduction of microorganisms’ activities which lead to longer shelf life. In spite of this، some changes may occur in dried food during storage. Our goal was to evaluate effect of pretreatment (blanching)، variety and shelf life on quality of potato dried products (powder and cubes) to select proper usage duration and variety. Three cultivated potatoes of Golestan province of Iran (so-called Agria، Satina and Kenebek) were dried in two different dryer (hot air oven and microwave oven). Changes during shelf life were investigated by measuring ascorbic acid and reducing sugars content plus rehydration ratio (in 100ºC and 25). The factorial complete randomized design was selected as the statistical design. Results revealed that there was significant difference (p<0. 05) between cubes and powders amount of components. Also water absorption of the products and ascorbic acid content، showed a significant (p<0. 05) reduction during three months storage، so it was concluded that it was better to use dried products before this time. Also، products which were dried in hot air oven، had the highest percent of water absorption in 25 ºC water in the first month of storage but after three months، it was changed to 100 ºC water. But the products which were dried in microwave oven had the highest percent of water absorption in 100 ºC during alls storage time. At last، Agria، because of its brilliant yellow color and low amount of reducing sugars، was the most accepted variety and proper usage duration was before three months storage.

The current approaches applied for removing nitrate from drinking water، commonly uses many chemical additives that may have undesirable or unknown effects on human health and in some cases caused many by products more dangerous than nitrate in drinking water. In present there are few appropriate and economic processes in this field and because of water scarcity in many areas development a suitable technology for treatment of nitrate contaminated drinking water for application in actual scales is crucial. In this research we develop an economic process with high selectivity for nitrate removal and minimum disturbance in other drinking water quality parameters that utilizes only hydrogen and carbon dioxide، produced in a methanol based electrochemical gas generator by applying a very low DC voltage (5-10 volt). We evaluate the ability of hydrogenotrophic denitrification for removal of nitrate in a bioreactor packed by light expanded clay aggregates known as LEACA. The results showed by proper coupling of electrochemical gas generator and denitrification bioreactor only by injection of tow clean and harmless gases، hydrogen and carbon dioxide and without any other chemicals addition for common concentrations of nitrate in natural waters by hydraulic retention time of 2-5 hr، removal efficiencies greater than 95% can be achieved. Also in comparison with other conventional methods such as ion exchange، reverse osmosis، electrodialysis، and biological heterotrophic with organic carbon source this system has several advantages such as: high selectivity for nitrate ion، low biomass yields، low electrical energy consumptions، without any problems resulted from organic carbon source addition (for example: taste and odor problem، carcinogenic THM production in disinfection process and rapid clogging of biofilter)، easy operation، and compatibility with health issues in drinking water treatment.

Recently، many studies have been conducted to produce lactic acid. At present study، lactic acid production conditions from whey، in batch fermentation، by Lactobacillus casei were studied to optimize culture medium، using Taguchi method. Four different concentrations for nitrogen sources; yeast extract، peptone and ammonium sulfate; and 3 levels for temperature and shaker rate were selected. At predicted optimum conditions by Taguchi analysis، in batch fermentation and without pH control، after 24 hrs incubation، 12. 5 g/lit lactic acid was obtained.

Biophysical and chemical properties of oilseeds particularly sunflower seed plays important role in the proper design of equipment for handling، drying، separation، dehulling، conveying، storage and mechanical expression of seed oil. In this research، some biophysical and chemical properties of three hybrid sunflower varieties، Hysun33‚ Progress and Euroflore from four location، Aliabad، Golidagh، Kalale and Kalpush in Golestan province were studied for variations in linear dimensions، arithmetic mean diameter، geometric mean diameter، sphericity، surface area، true and bulk densities، porosity، 1000 seed weight، volume، moisture content، hull and kernel percent، major، intermediate and minor size distribution، oil percent in seed، kernel and hull which determined by using of standard methods. The results showed that the length and geometric mean diameter of sunflower seeds varied from 8. 800 to 10. 987 mm، 4. 651 to 5. 979 mm، respectively. Within these data minimum and maximum values related to Golidagh Euroflore variety and Kalale Progress variety، respectively. The results of ANOVA shows that all of gravimetric properties of seeds such as 1000 seed weight، bulk and true densities، porosity are significant at the 0. 01probability level. Percentage of large seeds and hull varied 3. 580 (Aliabad Hysun33) to 28. 487 (Kalaleh Progress) and 25. 792 (Aliabad Hysun33) to 28. 825 (Kalaleh Hysun33)، respectively. At the end، with attention to interaction effect of variety and locations on characteristics of sunflower seed، the samples should be detached before handling and delivering to oil extraction industry.

Aflatoxins are mold secondary metabolites produced by species of Aspergillus. Aflatoxin causes acute and/or chronic poisoning and exhibits carcinogenic، mutagenic and teratogenic effects. Lactating cows fed with B1 aflatoxin-contaminated feed transmit the toxin، as the metabolic form aflatoxin M1 (AFM1) to the milk. When cheese is made from AFM1 contaminated milk، the toxin can be carried over to cheese. In this cross - sectional study، 188 samples were obtained from market in summer and winter and AFM1 levels were determined by ELISA method. AFM1 was found in 133 (70. 7%) samples. The mean of AFM1 concentration was 343 ng / kg. AFM1 levels in 68 samples (36. 2%) exceeded the maximum tolerance limit accepted by some European countries. Statistical analysis showed that concentration of AFM1 in cheese samples taken in winter (495 ng/kg) were significantly (p < 0. 05) higher than those taken in summer (191 ng/kg). In conclusion، incidence of AFM1 was high among cheese samples what must be regarded as a health concern for consumers.

The terminal velocity and coefficient of friction data are necessary for designing of handling and separating equipments. The terminal velocity data are also valuable in designing pneumatic conveying، fluidized bed dryer and cleaning equipments. In this paper، the terminal velocity and coefficient of static friction of saffron flower and its components (stigma، stamina، petal and stem) were determined as a function of moisture content. The experiments were conducted on saffron flower selected from fields of Kashmar. The data was statistically analyzed using factorial experiments with completely randomized design. The results showed that the terminal velocity of the saffron flower، stigma، stamina، petal and stem at moisture content of harvesting level to 40% (w. b.) were in the range of 1. 03 to 5. 13 m/s. With decreasing moisture content from harvesting level to 40% the terminal velocity of the flower and stem decreased significantly but the terminal velocity of the stigma، petal and stamina were not decreased significantly. The terminal velocity of the petal was the minimum value at the three moisture content levels. The coefficient of friction of saffron flower and its components on the friction surfaces were in the range of 0. 52 to 1. 1. The friction coefficients of all the components except the stem were the maximum values on polyethylene surface. The coefficients of friction were the minimum values on galvanized iron surface for all of the components. With decreasing moisture content from harvesting level to 40% (w. b.) the average values of coefficient of friction increased significantly for all of the components. The coefficient of friction of the stigma and flower were the maximum and minimum values، respectively at different levels of moisture content. Generally، at moisture content of harvesting it is possible to separate the flower، petal، stamina، stigma and stem from each others with changing air stream velocity. As well، it is possible to separate the petal from the others components at moisture levels of 70% and 40% (w. b.) using wind column device.

Bread has great importance in nutritional needs in Iran. The main kind of the breads are flat breads, they have got short shelf life, and there high percent of wastage in the case of this types of bread. Since the way which these breads preserves is important and one of the preservation method is freezing. the aim of this work was the study of the effect of the freezing and freeze storage on freeze thaw and the qualitative characteristics of Lavash bread. The raw materials were prepared, chemical specifications of the frozen Lavash (different panel) after thawing, studied. The Level of retrogradation with the DSC and the textural properties of the breads determined with the Instron. The sensory properties evaluated by the ranking method and was done by trained panels. The statistical parameters were measured by descriptive statistics One-way ANOVA and Tukey's test. The ranking method use for analysis of sensory scores. Results showed that within period of freeze storage, the retrogradation stops, and the force needed to make the slices of the bread was related to the period of freeze storage and there were significant (p<0.001). The amount of the retrogradation for the breads thawed by heat. The amount of the force needed for the slicing of the breads had significant differences and from sensory point of view the breads which thawed by the heat has higher score than the breads thawed at R.T. The results of this research indicated that, the Lavash bread was not affected that much by freezing, processes quality, and when it is thawed by heat it showed better quality and high acceptance by consumer, as a result, freezing method can use for Lavash bread storage and heat can be use for the thawing of bread.