فصلنامه پژوهش و نوآوری در علوم و صنایع غذایی
سال یکم شماره 3 (پاییز 1391)

Omega-3 fatty acid is used in daily healthy diet and plays an important role in prevention ofdisease. Being a considerably main source of Omega-3 fatty acid groups, fish preservation against oil oxidation and any other similar causatives seems quite necessary. In this study chitosan coated alpha tocopherol antioxidant was used in order to reduce oxidation corruption rate in farmed trout flesh. To meet the purpose a 2% Chitosan solution and chitosan enriched with alpha tocopherol in two concentrations (0.2% and 0.4%) were prepared for coating the trout samples. Samples were stored in fridge for 28 days and were tested every 7 days in terms of (PV), (AV), (TV) and (FFA) indexes. Fatty acid profile also determined by Gas chromatography assay in the fresh fish oil and after 3 weeks at the refrigerated FFA storage samples. Analytical results revealed that in comparison to the control samples, fewer changes were occurred in PV, AV, TV and FFA, proportion of n3 polyunsaturated fatty acids and 22:6 n3/C16:0 ratio between chitosan and chitosan-alpha tocopherol treated samples during the storage time. There were significant differences between treatment with chitosan and chitosanalpha tocopherol in trout samples (p < 0.05). Minimum oxidative changes were observed in 0.4% Chitosan alpha tocopherol treated samples.

The current research studies the qualitative characteristics of Iranian brand chipsaccording to the extracted oil from the products. In this experiment, seven samples ofpotato chips (salty) including 5 Iranian samples (T1, T2, T3, T4, T5) and 2 foreign brands(T6, T7), were evaluated by different kinds of qualitative methods. Experimentalparameters that had been examined in this research include measurement of theextracted oil percentage, oil oxidative stability, Iodine value and profile of fatty acidswas performed by GC. The findings showed that the percents of extracted oils fromseven potato chips samples were in the range of 24/24 (T6) - 41/55(T4). In order to setcriteria for oxidative stability of oil by rancimat test, the sample T4 (32/91) has thehighest oxidative stability of oil and other samples were as this sequence:T3>T5>T2>T7>T1>T6. Also the range of Iodine value changes 54/20(T7) – 105/93(T6) gr/100gr, and there is a negative relation between stability time and Iodine value. Thesaturated fatty acid, mainly represented in the samples, was palmetic acid andunsaturated fatty acids mainly oleic acid. The amount of oil in all potato chips samplesof this study were within the Iranian National Standard range, while the foreign brandscontained lowest amount of oil content.

In recent years, the uses of natural antimicrobial compounds, including extracts and herbal powders as preservative compound of the food are increasingly popular. The aim of the study was to evaluate antimicrobial effect of extract and powder of lamiaceae plants (thymus vulgaris L., Mentha spp. and Ziziphora tenuir L.) over prevention of pathogenic bacteria (Staphylococcus aureus) growth by examining industrial Doogh samples. For this purpose, three extracts contained (0, 0.075, 0.15 v/v) and powder contained (0, 0.075, 0.15 v/v) were prepared. Bacterial population decrease or survival in doogh samples were examined according to Staphylococcus pure strains in a 24 hours time within separate rounds by measuring the kinetics of bactericidal effects, using response surface design. Analysis Results in the inhibition effects of natural antibiotic agent in the Doogh samples revealed that: the powder of Lamiaceae family have greater effects on decreasing population of Staphylococcus than extracts. The best amounts of powder for decreasing pathogenic bacterial population were as flowing, Thymus 0.09 (v/v), Mentha 0.06 (v/v), and Ziziphora 0.14(v/v). In these circumstances greatest reduction of Staphylococcus population in 24 h is 1.98 Log/ml.

Successful development of rice bread for people allergic to wheat gluten has led to study of physicochemical properties of rice that affected rice bread characteristics. Samples of experimental Iranian rice breads baked in a home bread machine were evaluated by physicochemical methods and compared to Iranian rice cultivars (Tarom, Shiroodi, Neda, Fajr, Ghaem and Binam). Qualitative evaluation was conducted according to specific volume, oven spring, the height to diameter ratio, crumb to crust ratio, porosity and textural properties. In addition scanning electron microscopy (SEM) was applied for crumb characteristics. As a result to selection of the most suitable rice cultivars, we could develop the rice bread, of which loaf specific volume and physical properties are acceptable. These results showed that Binam cultivar had good physical properties and quality for making gluten-free rice bread.

In this study, the effect of Persian gum (PG) concentration (0.25-1%), oil-phase volume 5- 15%), the presence of whey protein concentrate (WPC) 1%, pH (3.5–8), and storage time (up to 20 days) on the stability, rheological properties, particle size distribution, as well as microstructure of emulsions prepared by ultrasound homogenizer was investigated. According to findings, PG was able to stabilize the emulsions particularly at higher concentrations likely via viscosity increasing but not due to its effect on lowering the interfacial tension. In addition, at higher pH (8) values, the stability of emulsions increased, whereas at pH 3.5, the rate of phase separation increased. Moreover, at pH 7 the stability of emulsions containing WPC was significant, while the phase separation observed at the presence of Persian gum (0.5 1%), probably due to depletion flocculation and thermodynamic incompatibility. Moreover, at pH 3.5 and 5, the creaming occurred with high rate likely because of the bridging occurred between protein coated droplets and gum and protein–gum coated ones. It can be concluded that firstly, the higher levels of gum lowered droplet coalescence and secondly, soluble part of PG as an adsorbing polymer was not able to bind to WPC coated droplets at neutral pH.

Medlar is a widely growth in northern Iran and used as an edible fruit as well as in home remedies. In this study, the antioxidant properties and total phenolic contents of acetone, methanol, ethanol 80% and water extracts of medlar (Mespilus germanica L.) were examined. Maximum amount of phenolic compounds were obtained with acetone (80%), followed by methanol, ethanol and water. Total phenolic content of acetone extract was 7.437 g GAE/100gr dried matter. Antioxidant activity was evaluated using three different methods including scavenging effect on DPPH radicals, reducing power of Fe+3 and total antioxidant capacity. The results were compared with the antioxidant capacity of a synthetic antioxidant, BHT. Acetone extract displayed the highest antioxidant capacity in all the assays. In addition, the effect of temperature (50 °C and 100 °C), pH (3, 5, 7 and 9) on the antioxidant activity of acetone extract was investigated. The antioxidant activity of the extract remained unchanged at 50°C and was at maximum pH (5.0). Results showed that, medlar was found as a potential source of natural antioxidants due to its marked antioxidant activity.