مجله علوم و صنایع غذایی ایران
سال نهم شماره 1 (پیاپی 34، بهار 1391)

Production of high volume of sludge is an important problem in wastewater treatment plants that necessitates approach of a proper economical and environmental management method. Chemical conditioning is used for increasing sludge dewater-ability and its volume reduction. Researchers have shown that use of natural compounds have environmental superiority over chemical ones. Therefore، in this research the effect of three food wastes including starch، white bean and pomegranate skin extract on the sludge dewatering capability in lab scale batch system was investigated. From the results، pomegranate skin extract in optimum pH of 4 and concentration of 1000 ppm gave the best efficiency. In this case، the amount of TTF، sludge cake humidity، volume of filtered water in 10 second، sludge volume reduction and turbidity were 10 seconds، 88. 31 percent، 50 ml، 25. 55 percent and 24 FAU، respectively.

The present study was conducted to evaluate the effect of antimicrobial coating on the shelf-life of trout fillet. Antimicrobial coatings were obtained by incorporating cinnamon oil in coating formulations prepared from chitosan. Coated fish were stored at refrigerated (4±1˚C) and were periodically evaluated for Total viable counts، psychrophilic counts، lactic acid bacteria and Enterobacteriaceae as well as total volatile basic-nitrogen (TVB-N) and pH. Sensory evaluations were performed for Texture، odor، color، overall acceptability. Results showed that cinnamon oil and chitosan coating had synergistic effects (P < 0. 05) in reducing the Total viable counts، psychrophilic counts، lactic acid bacteria and Enterobacteriaceae. Chitosan coated enriched with cinnamon significantly (P < 0. 05) reduced chemical spoilage as reflected in TVB-N. Texture، odor، color، overall acceptability significantly (P < 0. 05) changed only for the control samples.

Status of heavy metal contamination of foods with animal and aquatic animal origin in Iran The status of heavy metals contamination in foods with animal and aquatic animal origin was studied. In spite of limited studies about foods (except fish and edible marine foods)، data shows low contamination of milk with lead but relatively high level of cadmium in this product. Iron contamination was found in high level in milk in the industrial areas. Concentrations of lead and copper were found relatively high in some imported infant milk powder. In some fishing areas in Khazar، the concentrations of lead and cadmium were higher than international standards. The same situation is seen in south sea’s fishery products for lead، cadmium and nickel. In a survey in 2005، mercury level was found higher than permitted level in white fish hunted from central Khazar’s fishing area. Shrimp was found relatively free and safe for heavy metal contamination. Other marine foods such as oyster contamination with nickel and vanadium were observed. The sole study about red meat shows lead contamination in low percentage of studied samples.

Watermelon juice was concentrated by heating at three different temperature-pressure matches (at atmospheric، 38. 5 and 7. 3 kPa) and 100، 75 and 40°c. The effect of operational pressure-temperature on evaporation rate، pH، viscosity، density and lycopene content of watermelon juice versus time of concentration was evaluated. The result was shown that the higher vacuum degree lead to higher evaporation rate and better preservation of lycopene content as well. The pH of samples didn''t change during heating concentration. It was shown there is a linear correlation between density and concentration degree of samples. Also viscosity of samples is independent of operational pressure and it is only depend on concentration degree.

In this paper، the effect of type and concentration of some sweeteners (sucrose، glucose، fructose، aspartame، acesulfame k and neotame) has been investigated on the reheological properties of guar gum solutions in a model system include sweeteners and hydrocolloid. Two level of sweetener concentrations were used (10، 20% for sucrose، glucose، fructose، and 0. 1، 0. 2% for aspartame، acesulfame k، and 0. 001، 0. 002% for neotame). The rheological properties were measured by oscillatory rheometer (model MCR-300). The results showed that the effect of sweeteners on rheological properties of guar gum depend on type and concentration of sweeteners. In these concentrations، the synthetic sweeteners had no effect on rheological properties of guar gum solution.

To determine some mechanical properties of garlic bulb and its cloves، some mechanical tests was performed on a variety of Talesh local garlic at three levels of storage period with 70-day intervals. Mechanical tests are performed on three levels of loading speed and three levels of storage period. Compressive tests were performed on bulb، cloves، and on cylindrical samples taken from the tissue of garlic cloves. According to analysis of variance based on factorial experiment in randomized complete block design، the value of module of elasticity، maximum force required to rupture and toughness of cloves were measured respectively 2. 762MPa to 7. 091MPa، 105. 043N to 167. 27N and 62. 358mJ/mm3 to 101. 44mJ/mm3 and also the value of young module of elasticity، the maximum force required to rupture and toughness of cylindrical samples taken from tissue of garlic cloves were measured 3. 368MPa to 6. 981MPa، 12. 606N to 25. 762N and 0. 173mJ/mm3 to 0. 33mJ/mm3 respectively. The ranges of value of force required to loosen the bulb، while loading along the height and width direction، were measured 127. 023N to 228. 001N and 45. 52N to 106. 97N respectively.

In this study Response Surface Methodology (RSM) was employed to investigate the effects of different operating conditions on the hydrolysation process of poultry by-products protein by the alcalase. Central Composite Design (CCD) by 5-level and 3-factor was used for the optimization of the hydrolysate production and to evaluate the effects and interactions of process variables: time (minute)، temperature (C◦) and enzyme to substrate ratio on the response. The response was included degree of hydrolysation (%). The mathematical model showed good fit with the experimental data، since the R2 of 0. 96 indicated that 96% of the variability within the range of values studied could be explained by the model. Furthermore lake of fit of the model was not significant (p<0. 05). The optimum conditions for production of poultry by-products protein hydrolysate by 15. 24% degree of hydrolysis were established as an enzyme activity to substrate ratio 0. 07 AU/g protein; time 127. 69 minute، and temperature 52. 51°C. According to amino acid analysis and chemical score، methionine and histidine was the limiting amino acids in the hydrolysate. The poultry by-products protein hydrolysate tends to be a potential source in balanced fish diets and functional additive in food industries.

Strawberry fruit is popular for fresh eating but it has a short shelf and rapidly infected The consumer demanded to prolong its shelf life. Chitosan is a natural biopolymer which has an antimicrobial effect on fresh fruits and vegetables. Some essential oils also have the antimicrobial activity. The combination of these two agents can be applied in order to prolong the shelf life of fresh fruits and vegetables. In this study 0%، 0. 3% and 0. 5% of chitosan solutions، 1 mg/l of vanillin + 0. 3%of chitosan and 1 mg/l of vanillin + 0. 5%of chitosan solutions were used to coat strawberry. Fungi isolated from an infected strawberry fruit، after screening was incubated to the fresh fruit coated with the prepared solutions and kept in refrigerator at 4 o C. The solid soluble materials، ascorbic acid and the titerable acidity were measured before and after the coating. The results showed chitosan plus vanillin can prolong the shelf life of the strawberry up to 18 days at 4 o C.

Antimicrobial packaging is a form of active packaging that could extend the shelf-life of foods and provides microbial safety for consumers. In order to control undesirable microorganisms on food surfaces، volatile and non-volatile antimicrobial agents can be incorporated into polymers. Incorporation of essential oils and other antifungal agents in edible films composition is an antimicrobial packaging that able to inhibit fungal growth on the pistachio and aflatoxins production. The antifungal activity of Sage (Salvia officinalis) extracts against Aspergillus flavus in whey protein concentrate-based coating on pistachio kernels was investigated. The antifungal effect of Sage extracts was investigated in culture media by direct method (well method) and application of whey protein concentrate (WPC) films as discs (disc method) incorporated with different concentrations of extracts. In order to evaluate the antifungal effect of extract in pistachio، kernels coated with different concentrations of extract inoculated with a culture media discs contain 9-day-old growing A. flavus colony and the growth rate of inoculated discs were measured during 1 week. In experimental condition، minimal inhibition concentration was achieved by 155 ppm of ahcoholic extract (30 percent concentration). The results also showed that WPC coating incorporated with 4000 ppm of Salvia officinalis extracts on pistachio kernels inhibited A. flavus growth totally. Paying regard to economical aspects of importance of contamination with toxigenic fungi in pistachio kernel suggest the application of Sage extract incorporated in edible coatings for toxigenic fungi growth and toxin production in foods.

Due to disadvantages of synthetic packaging materials such as migration into food، polluting of environment، difficulty of recovery، high costs of raw materials and production، also modifying properties of starch based edible film، in this study different kinds of edible films from starch and tragacanth (Iranian gum) will be formulated and their properties investigated. In this regard، edible films formulated by mixing potato starch، tragacanth (1-5%)، Glycerol plasticizer (10-40%) and sunflower oil (0-20%)، then the film mechanical (tensile strength and elongation)، optical، solubility and water vapor permeability (WVP) properties measured. The results showed that physical and mechanical properties of potato starch-based edible films were affected by the content of tragacanth، glycerol and sunflower oil. The tragacanth gum increased tensile strength and reduced chroma، while glycerol reduced tensile strength and increased elongation at break. Also، the sunflower oil decreased solubility and water vapor permeability and increased elongation. Finally، amounts of 2% tragacanth، 30% glycerol and 17% sunflower oil were determined as optimum points for production of starch based edible films with optimum properties.

In this study، some physical properties of two wheat (Alvand cultivar) and wild oat and the effect of humidity on these properties was investigated. The effect of Grain type (wheat and oat) and humidity (9. 45، 12 and 14. 45%) on triple grain size، geometric mean diameter، sphericity index، bulk density، particle density، porosity، static coefficient of friction and terminal velocity in the factorial design was evaluated. The results showed that the Grain type and moisture levels، are significant effect on the physical properties of oat and wheat grains. There are exist significant differences between wheat and oat in terms of particle density، Bulk density and porosity. Also the moisture effect on the bulk density at 1 percent and on the particle density at 5 percent but by its effect on the percentage porosity was not significant. There was highly significant differences between the friction surfaces، Graine type and moisture levels. Between surfaces، aluminum، were Maximum and steel the lowest coefficient of friction. The coefficient of static friction and the terminal velocity increases linearly as moisture increased.

Antioxidant properties of plant extracts are apparently related to the content of their phenolic compounds. In this study، phenolic compounds from two acorns varieties namely Q. branti var persica (Q. b) and Q. castaneifolia var castaneifolia (Q. c) were extracted with methanol (80%). After evaporation with rotary evaporator، extracts were dried with freeze drier. The concentrations of phenolic compounds in the extracts were determined according to the Folin-Ciocalteu method، and results were expressed as tannic acid equivalents per gram of dried extract (TAE/g d. e). Castaneifolia variety had the highest phenolic content with 217. 65 (TAE/g d. e). Antioxidant activity of methanolic extracts were studied in sunflower oil and compared with synthetic antioxidants، by measuring their peroxide and thiobarbituric acid values during accelerated storage. Methanolic extracts of acorns at three different concentrations (250،500 and 1000 ppm) and synthetic antioxidant at two concentrations were added to sunflower oil. Both extracts retarded the oxidation of sunflower oil at 70°c more efficiently than BHA and BHT. The peroxide and thiobarbitoric acid values of control samles were raised to 328. 88 (meq peroxide/ kg oil) and 0. 58 (mg malon aldehyde/kg oil) after tewelve days storage while this values were 176. 36 and 0. 332 for oil sample contain 1000 ppm methanilic extract of Q. c and 183. 2 and for Q. b were 0. 374، respectively.

Antifungal drugs have an important role for treatment of fungal skin diseases of livestock and prophylaxis. These compounds belong to the different chemical groups but Imidazole group is one of the most important groups. In this study 60 pasteurized milk samples were analyzed by liquid-liquid microextraction and high performance liquid chromatography. And the efficiency of solid phase extraction and high performance chromatography-UV spectroscopy was evaluated in the extraction and determination of Ketoconazole and Clotrimazole analytes in milk. In this research، after full validation، detection and quantitation limits were 0. 01 μg. ml-1 and 0. 1 μg. mL-1 for Ketoconazole and Clotrimazole. The linear range of calibration was relatively wide (0. 01-100 μg. ml-1). The relative standard deviation was 0. 1-7. 5% for Ketoconazole and 0. 1-8. 5% for Clotrimazole. Monitoring of 60 pasteurized milk in different seasons for Clotrimazole and Ketoconazole residue with 0. 01 ppm detection limit، demonstrated there is no detectable amounts of these antifungal residues in pasteurized milk.