فهرست مطالب pirsa

In this work, pomegranate juice was adulterated manually by adding sour cherry and red grape juices. Physicochemical properties (brix, acidity, formalin index, reducing sugar, and total sugar) and Volatile Organic Compounds (VOCs) gas chromatography profile (extracted by PPy-Ag nano-fiber) of pure pomegranate juice and adulterated pomegranate juice were evaluated and used to find adulteration. PPy-Ag nano-fiber as a Head-Space Solid Phase Micro Extraction-Gas Chromatography (HS-SPME-GC) method was used to extract and detect the VOCs profile (total peak area and total peak height) of different juices. The Box-Behnken Design (BBD) was used to study the effects of Pomegranate Juice (PJ), Sour Cherry Juice (SCJ) and Grape Juice (GJ) percent (V/V%) in the adulterated mix juice physicochemical properties and GC-profile. Results showed that the percent of pomegranate juice, sour cherry juice, and grape juice affect the juice physicochemical property, and there are relations between the physicochemical property of the juice and VOCs gas chromatography profile (total peak area and total peak height) that can help to find adulteration. The presented research makes it possible to detect adulteration of sour cherry and grape juice and their percent in the adulterated mix by analyzing the juice physicochemical properties and GC-profile.

Iranian famous drinking yoghurt type, named Doogh, is a fermented dairy beverage and constituts an important part of daily beverage consumption in Iran. Doogh is commonly produced from mixing of yoghurt, drinking water, salt, and essence of aromatic vegetables such as thyme, mint, and oregano. In the present work, the effects of Quince seed mucilage [Qm: 0-0.1% (w/w)], Guar gum [Gg: 0-0.2% (w/w)] and storage time (1-21 days) on the physicochemical (pH, acidity and viscosity) and sensory properties of Doogh were studied. The Doogh was stored at 4°C for 21 days to be evaluated. Quince seed mucilage and guar gum were added to Doogh based on a Central Composite Design (CCD). The Response Surface Method (RSM) was applied to find out the optimum conditions and interaction between different factors. Three factors including Doogh storage time and added percentages of Qm and Gg were investigated. The results showed that the optimum condition of factors was different based on response. Based on viscosity of the Doogh, the first day of Doogh production and 0.1% (w/w) of Qm and 0.2% (w/w) of Gg were the best condition.

Nanostructure polypyrrole (PPy) (50-10 nanometers) and polypyrrole-ZnO (PPy-ZnO) nanocomposite (30-120 nanometers) were synthesized on the commercial polyester fiber by chemical polymerization at room temperature. The synthesized fibers were used as humidity sensor to detect and determination of moisture of flour samples. Headspace method was used to sampling and injection of flour moisture to designed sensor. Results showed that PPy and PPy-ZnO sensor have the good ability to the determination of flour moisture but PPy-ZnO sensor has better response and is more sensitive than the PPy sensor. An experimental design based on central composite design (CCD) was used to study and optimize some factors like flour mass, time and temperature of sampling that affect determination and analysis of flour moisture. Results showed that the optimum condition based on fiber type (PPy or PPy-ZnO fiber) is different. In the optimum condition figure of merits of sensors to determination of humidity were calculated. PPy and PPy-ZnO sensor easily could determine flour humidity from 0.01 to 0.25 %.

Polypyrrole is one of the conducting polymers that easily synthesized on the different substrates at low temperature. In this work a nanosized polypyrrole (PPy) coated polyester fiber was provided by chemically-deposition of PPy on the surface of polyester. The PPy fiber was employed to the extraction of volatile organic compounds (VOCs) in yogurt samples as an extraction agent. The effects of Quince seed mucilage (Qm) and storage time on the sensory, physicochemical properties, total peak area and the total peak height of volatile compounds of yogurt in gas chromatography (GC) were studied. A factorial design with central points and star points was applied to design the experiments and find out the interaction between different factors and relation between sensory and physicochemical properties and GC parameters (total peak area and total peak height) of yogurt. The results showed that the yogurt sample acidity is increased by increasing of storage time and yogurt sample modified by mucilage has more acidity than blank yogurt, quince seed mucilage and storage time affect sensory and physicochemical properties of yogurt. There is good relation between sensory properties and GC parameters of yogurt, so it is possible to determine quality, odor, storage time and other properties of yogurt samples by gas chromatographic analysis of yogurt.

The aim of this research was to study the physical and antioxidant properties of bacterial cellulose based active films containing Scrophularia striata extract. The effect of β-cyclodextrine (β-CD) and lamination process
was investigated on the properties of films. Results showed that the laminated films had the highest thickness. Water solubility of the films was increased by incorporation of the extract, but this property was decreased after lamination. Moisture uptake and water vapour permeability were decreased by β-CD inclusion and lamination process. a value, Yellowness index and total colour difference were increased significantly by addition of extract (p ≤ 0.05). But the effect of β-CD and lamination was not significant on colour properties. β-CD containing three-layer film had the highest tensile strength (15.11 MPa) and Young modulus (13945 MPa). Bacterial cellulose film containing extract showed a good DPPH radical scavenging activity (54.5%), but lamination process caused to decrease the antioxidant activity. Generally complex formation of extract with β-CD and also lamination was able to decrease the negative effects of extract on physical properties of bacterial cellulose film and to fabricate an active film with high antioxidant activity.

Determination of 1, 1-dimethylhydrazine (DMH) in air is carried out by spectrophotometry, GC or HPLC analysis, but in this study DMH was analyzed by a gas sensor based on nanostructure conducting polyaniline. Determination of DMH has been done very simplely and quickly in recent work. Electrically conductive fibers have been prepared by polymerization of aniline on surfaces of commercial polymer fibers in the presence of an oxidizing agent. The resistance of poly aniline (PANI) coated fiber sensor (PANI-FS) was investigated and related to coating conditions, which was controlled by adjusting the reactant concentrations. The morphology of the conducting film on the surface of the fibers was examined by scanning electron microscope (SEM). The sensing behavior of PANI in the presence of some volatile organic compounds (VOCs) is studied experimentally. The PANI sensor had demonstrated to have good sensitivity for DMH and good reproducibility when reused.