نشریه نوآوری در علوم و فناوری غذایی
پیاپی 8 (تابستان 1390)

In this study, a biodegradable composite for food packaging application was produced. Low density polyethylene as matrix, lingo-cellulosic powder of wheat straw as filler, and MAPE (Maleic Anhydride Polyethylene) and PEG (Polyethylene Glycol 400 and 600) as compatibilizers were used to preparation of these biocomposites. Mechanical characteristics (tensile, three points flexural and impact tests) of samples were performed to produce the best compound regarding the compatibilizers effect. Different weights of filler phase in levels: 70 to 30, 60 to 40, 50 to 50, and 40 to 60 % were used in the composite formulation. Compatibilizers were also applied in three levels of 0, 7, and 10 %. The results showed that the MAPE was the best compatibilizer as to improving the mechanical properties of the compounds. The type of compatibilizer is ineffective on the impact results. All composites were better than the control sample in the flexural tests.

Two types of yoghurt including fresh cow's milk and powdered milk were produced according to typical production methods. Physiochemical, rheological and organoleptic properties of yoghurts were analyzed during 21 days of storage. Rheological measurements revealed an obvious shear thinning profile for both samples. Power law was shown to be useful for description of flow behaviour of samples and it was found that flow index behaviour was less than unity. Yoghurt from fresh milk had a larger consistency index than powdered milk yoghurt, but flow index behaviour was lower indicating higher shear thinning property. Viscosity of both samples showed significant variations during 21 days of storage. Flow index behaviour for samples decreased during storage which indicates more shear thinning behaviour of the samples and this is due to a decrease in Total Dry Solids of the samples. During storage time pH decreased while acidity increased. Fat variations were significant at 5% level from the first day until the th day and such variations showed a decrease trend. Yoghurts from powdered milk showed a more stiff texture than yoghurts from fresh milk. Yoghurts from powdered milk have a higher acceptability between panelists than yoghurts from fresh milk and this is because of the similarity in exture, lavor and odor of the final product.

Listeria spp. is a ubiquitous organism. This microorganism has been isolated in many ready-toeat seafood products including smoked fish. Listeriosis is a food-born disease that mostfrequently affects infants and adults whose immune systems are weakened. The preseent study was undertaken to determine the prevalence of Listeria spp. in fresh and smoked silver Carp (Hypophtalmichthys molitrix). Surveys of fresh fish indicated that 40% of the samples were found to be contaminated with the organism L. monocytogenes and L. innocoa were isolated from 33% and 20% samples respectively. The results obtained during the examination of smoked silver Carp (gutted and ungutted fish in smoke time 3) indicated that both species can survive in all smoked treatment. Thus, cold smoking (30 oC) did not reduce the counts of Listeria spp. in this study, the incidence was higher in ungutted samples than gutted samples. Bacterial load changed significantly along the smoking time period (p<0.05).

Algae organisms are rich sources of biologically active metabolites which can be used in pharmaceutical industry. The purpose of this study was to evaluate Chlorella vulgaris acetone and ethanolic extracts for antimicrobial effects against Bacillus subtilis. The algae extract was investigated for in vitro antimicrobial activity against Bacillus subtilis PTCC1156 using disk diffusion and dilution method.It was found that the Chlorella vulgaris has good inhibitory effect on Bacillus subtilis. Inhibitory effects of each extract varied considerably among the microorganisms. Maximum antibacterial activity was observed in acetone extracts. Its MIC against Bacillus subtilis WAS determined 3 g/mL.

In this paper, the effect of microwave heating on sunflower, soybean and peanut oils was studied. Each oil was heated for 2, 4, 6, 8, 10, 12, 15 and 18 minutes in microwave oven. Peroxide value, free acidity, colour absorbance, total tocopherols, conjugated diene and triene were measured. The results showed that the amount of peroxide value, colour absorbance and acidity were proportionally increasing with the increase of heating period. It was found that the total tocopherols of the microwave heated oils, decreased depending on the type of the predominating tocopherols. Also polyunsaturated fatty acids generally decreased by increasing the heating period.

With regard to the significant functions of nuts in preventing cardiovascular diseases and certain kinds of cancer as well as their high consumption in our country, the present research was conducted to identify some characteristics of Iranian nut oils including walnut, almond, pistachio with cultivars Damavand, c.v.b12, Ahmad Aghaee with %4, Momtaz by measuring the total phenolic compounds using folin assay, identifying fatty acids profile by GC, oil oxidative stability at three different temperatures: / by Rancimat method and measuring other oxidative stability by Oven Test. Folin assay results showed that walnut consists the most phenolic compounds, then were pistachio and almond, respectively. Rancimat test results indicated that pistachio possessed the highest oxidative stability in each of three mentioned temperatures and then were almond and walnut, respectively. The results of the other oil oxidative stability showed the most oxidative stability among the mentioned oils and the conclusion of variation trend of peroxide index with less rate was in pistachio and then were almond and walnut, respectively. The important results of the fatty acids profile indicated that pistachio contained the most saturated fatty acids and the least saturated fatty acids belonged to walnut. Among the mentioned oils, almond oil had the least poly-unsaturated fatty acids and walnut had the most one. In addition, almond possesed higher oleic acid, then were pistachio and walnut, respectively. According to these findings and inspite of having high phenolic compounds in walnut oil compared with other mentioned oils, it is concluded that the profile of fatty acids has a more effective and crucial role in the stability of oils oxidation.

Effects of environmental pollution on food safety for human consumption is a serious global issue. Considering the serious effect of the heavy metals on public health level, measurement of concentration of toxic heavy metals in highly-consumed foodstuff such as salt, bread and water may pave the way for discovering the causes of many diseases. In this research, determination of heavy metal amounts like Fe, Pb, Cu and Cd in the samples of washed salt by water and rock salt by the flame atomic absorption spectroscopy were investigated. Mean (Mean  Standard Error) concentrations of heavy metals in salt were: Fe(3.89 ± 1.63), Pb(0.55 ± 0.47), Cu(0.29 ± 0.15) and Cd(Not detectable) (μg g-1) dry weight respectively. For rock salt, mean (Mean  Standard Error) concentrations were: Fe(8.30 ± 0.27), Pb(1.21 ± 0.08), Cu(0.89 ± 0.06) and Cd 0.17± 0.03) (μg g-1) dry weight respectively. These values were compared with each other and with allowed standard of these elements for salt as defined by the institute of industrial research and standard of Iran. Statistical analysis indicated that there is no significant difference between values of mean heavy metals Fe, Pb, Cu, Cd, in purified salt, rock salt and Iranian salt standard (P>0.05). However, with rock salt being washed out a significant change in purity from 96.98 to 98.83 mass percent was obtained (P<0.05).

Drying process for seasonal products such as rhubarb which are available only a few months in a year for consumers is very important، because this process not only prevents the spoilage of these products but also makes this consumption possible throughout the year. In this study، after drying rhubarb''s stems and preparing rhubarb powder، the quality indices including: acidity، moisture content، pH، color intensity، bulk density (loosed and packed)، vitamin C and solubility، were measured for samples which had been dried in a cabinet tray drier at 50، 60 and 70 C، and also those dried in the traditional method. Finally sensory evaluations were performed to select the best formulation for preparing condiment from rhubarb powder. The results of the study showed that the drying process at 70°C was the optimal condition because it had the least time and maximum rate of drying. For preparing condiment from rhubarb powder the formulation that consist of 5 g white pepper، 2/5 g mustard powder and 2/5 g Indian nutmeg powder was selected as the best formulation by the panelists. The comparison of the samples dried under different conditions in terms of quality indices revealed that the traditional method was the least suitable.