Influence of enzymes on rheological,microstructure and quality characteristics of parotta—an unleavened Indian flat bread

Enzymes are used in the baking and milling industries to control dough properties and improve the quality of finished products. The role of enzymes in the baking process of an unleavened Indian flat bread, namely South Indian parotta, was studied. In this connection, comparisons have been made on the effects of different enzymes such as fungal α‐amylase (FA), glucose oxidase (GO), proteinase and xylanase on rheological characteristics and microstructure of parotta dough and its relation to the overall quality characteristics of baked parotta. Addition of GO increased, while FA, xylanase and proteinase decreased farinograph stability. Extensograph resistance to extension increased with GO or xylanase and decreased with FA or proteinase. The extensibility increased with FA, xylanase or proteinase and decreased with GO. The microstructure of parotta dough with different enzymes revealed that the use of proteinase improved the continuous gluten formation compared with the control and the other three enzymes, FA, xylanase and GO. This could be due to the proteinase enzyme breaking larger protein fibrils into smaller fibrils and thus enhancing the continuous gluten film formation. A similar observation was also noted in the microstructure of baked parotta layers. The microstructure of parotta with proteinase enzyme showed a continuous network of protein films compared with a cluster of protein films in parotta with GO. In the case of xylanase‐treated parotta, the starch granules were deformed completely and these deformed starch granules were found sticking to the protein films. In parottas prepared with GO and FA, only a few starch granules with faint outlines were visible. Generally speaking, the overall quality score of parotta decreased to 68 and 64 with the use of FA and, GO respectively, as against the control parotta score of 74. The score increased to 92 and 82 with the addition of proteinase and xylanase, respectively. Copyright © 2004 Society of Chemical Industry     

Effect of additives on the quality and microstructure of vermicelli made from<Emphasis Type="Italic"> Triticum aestivum</Emphasis>

The effects of various additives [xylanase (0.06, 0.012, and 0.018%), gluten (1.5 and 3.0%), ascorbic acid (0.01 and 0.02%), glycerol monostearate, sodium stearoyl-2-lactylate (SSL) (0.25, 0.50%) and glucose oxidase (0.1%)] on the quality of vermicelli made from Triticum aestivum was studied. The results revealed that xylanase at 0.012% produced an improved quality product in terms of increase in cooked weight, expansion in volume of strands, and firm texture without stickiness. The micrograph of vermicelli exhibited a uniform, continuous protein matrix. The yellow index values improved with addition of gluten (3%) and ascorbic acid (0.01%). The gluten added appeared as a prominent strong network in micrographs, imparting strength to the vermicelli as evidenced by higher shear values. SSL (0.5%) gave a firm, discrete product and the protein fibrils displayed a massive network, owing to the strengthening effect. At the level of glucose oxidase used (0.1%), it exerted an adverse effect on the product quality. In general, the additives lowered the cooking loss and the leaching of solids in vermicelli when compared to the control.     

Fabrication and optical modulation of top-emitting yellow light polymer light-emitting diodes on the FR4 board

Top-emitting yellow light polymer light-emitting diodes (PLEDs) were fabricated on the FR4 board for future application in optical interconnects. A 100 μm thick glass plate with sputtered Ag films on the back side for light reflection was bonded to the board for smooth surface. The PLED had a structure of indium tin oxide /poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)/phenyl substituted polypa raphenylene-vinylene/Ba/Ag and reached the brightness of 4528 cd/m² with a corresponding current efficiency of 7 cd/A. A small AC signal imposed onto a DC bias was employed to characterize the electroluminescence delay time and hole mobility in the PDY-132 super yellow films.     

Putative virulence genes of Vibrio cholerae from seafoods and the coastal environment of Southwest India

Shrimp, clam and oysters were obtained at two fish markets and at a fish landing dock, and plankton, water and sediment samples were obtained from four river estuaries, in southern India. The samples were analyzed for Vibrio cholerae by conventional isolation techniques and by polymerase chain reaction (PCR) procedures. V. cholerae was isolated from 2 of 5 shrimp, 2 of 5 clam and 5 of 20 water samples. All biochemically confirmed isolates of V. cholerae were positive for toxR. For direct detection of V. cholerae in enrichment broths, PCR was performed using lysates from 0 and 6 h enrichments. All the V. cholerae isolates and enrichment broth lysates were subjected to PCR analysis for the detection of the genes toxR, ctxA, tcpA, ompU, hly, ace, Nag-ST (stn/sto), and ompU. Enrichment broths of all the samples which yielded V. cholerae were positive for toxR, OmpU and hlyA genes, while one of a fresh fish market sample was positive for the ace gene. Choleragenic V. cholerae were absent from all environmental samples and fresh fish from the markets, but one sample of shrimp was positive for V. cholerae O139.     

Determination of chloramphenicol in shrimp by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS)

A liquid chromatographic method with electrospray ionization tandem mass spectrometric (LC-ESI-MS-MS) detection and identification is described for the determination of chloramphenicol (CAP) in shrimp tissue. Homogenized shrimp samples were extracted by liquid-liquid extraction using ethyl acetate. d5-Chloramphenicol (5D-CAP) was used as the internal standard. Data acquisition was in negative-ion multiple reaction monitoring (NMRM) mode using three transition reactions for CAP (m/z 321 --> 152, m/z 321 --> 257 and m/z 321 --> 194) and two for d5-chloramphenicol (m/z 326 --> 262 and m/z 326 --> 157). Method validation was carried out according to European Commission decision 2002/657/EC. The calibration curve was linear in the range 0.10-2.00 microg l(-1), with typical r2 > 0.99. The decision limit (CC alpha) and detection capability (CC beta) were 0.06 and 0.10 microg kg(-1), respectively. There was no influence of the matrix on the determination of chloramphenicol.     

An investigation of bread-baking process in a pilot-scale electrical heating oven using computational fluid dynamics

A computational fluid dynamics (CFD) model was developed for bread-baking process in a pilot-scale baking oven to find out the effect of hot air distribution and placement of bread on temperature and starch gelatinization index of bread. In this study, product (bread) simulation was carried out with different placements of bread. Simulation results were validated with experimental measurements of bread temperature. This study showed that nonuniform air flow pattern inside the oven cavity leads to uneven temperature distribution. The study with respect to placement of bread showed that baking of bread in upper trays required shorter baking time and gelatinization index compared to those in the bottom tray. The upper tray bread center reached 100 °C at 1200 s, whereas starch gelatinization completed within 900 s, which was the minimum baking index. Moreover, the heat penetration and starch gelatinization were higher along the sides of the bread as compared to the top and bottom portions of the bread.     

Effect of hydrocolloids and emulsifiers on the rheological,microstructural and quality characteristics of eggless cake

Effect of hydrocolloids like Arabic (AR), guar (GR), xanthan (XN), carrageenan (CG) and hydroxypropylmethylcellulose (HPMC) in combination with emulsifiers such as glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL) on the rheological, microstructural and quality characteristics of eggless cake was studied. Addition of GR to wheat flour in the presence of SSL increased peak viscosity, while in the presence of GMS all hydrocolloids excepting XN increased the peak viscosity. The set back value decreased with the addition of hydrocolloids. Addition of hydrocolloids to wheat flour as well as in the presence of GMS and SSL increased the eggless cake batter viscosity, specific gravity, and XN showed the highest value. Among different hydrocolloids tried, only HPMC improved the eggless cake making characteristics of wheat flour. Use of HPMC increased the overall quality score of eggless cake with GMS to the maximum extent followed in decreasing order by CG and XN. Addition of all the hydrocolloids increased the overall quality of eggless cake with SSL and highest improvement was brought about by HPMC. Microstructure studies of eggless cake crumb with hydrocolloids showed that the starch granules appeared wrapped by XN and HPMC. In eggless cake with combination of HPMC and SSL the protein matrix appeared more uniform.     

Improved magnetic and piezoresponse behavior of cobalt substituted BiFeO3 thin film

Piezoresponse force microscopy (PFM) technique has been utilized to characterize the nanoscale electromechanical properties of chemical solution deposited pristine (BiFeO₃, BFO) and 5% Cobalt-substituted bismuth ferrite (BiFe_0.95Co_0.05O_3, BFCO) thin films. Distinct PFM contrast was observed on the films' surface both in out-of-plane and in-plane modes. Piezoresponse signal was larger in BFCO film than BFO and the former film also exhibited negative self polarization. The calculated self polarization factor was − 0.94. Lateral signal (in-plane) changed its sign upon 180° sample rotation which ruled out spurious electrostatic contribution and confirmed piezoelectric nature of the effect. Square patterns were written by local poling and reversible nature of the piezoresponse behavior was established. Well saturated piezoelectric hysteresis loops were acquired with improved piezoelectric coefficient value in case of Co-substituted BFO film. The effect has been described on the basis of polarization rotation with doping. Magnetization of BFO film also increases with Co-substitution. The enhancement in magnetic and ferro/piezoelectric properties should be useful for multiferroic applications.     

Structural,microstructural, ferroelectric and photoluminescent properties of praseodymium modified Ba0.98Ca0.02Zr0.02Ti0.98O3 ceramics

The ‘x’ wt% (x = 0, 0.02, 0.04 and 0.06) Pr₆O₁₁ modified Ba_0.98Ca_0.02Zr_0.02Ti_0.98O₃ (BCZT – x Pr) piezoelectric ceramics have been fabricated by the solid state reaction method with sintering at 1450 °C (x = 0) and 1350 °C (0.02 ≤ x ≤ 0.06) for 2 h. The impact of Pr concentration on the structural, microstructural, photoluminescence and ferroelectric properties has been systematically investigated. The x-ray diffraction (XRD) patterns revealed the co-existence of tetragonal and orthorhombic phases at room temperature upto x = 0.04 Pr concentration. The grain size was found to decrease upto x = 0.04 Pr content. Room temperature Raman spectroscopy results were consistent with the XRD results. The photoluminescence (PL) spectra showed significant emissions consisting of strong blue (489 nm), green (528 nm) and red (649 nm) wavelengths. The emission intensities of PL spectrum were strongly Pr concentration dependent and a maximum value was obtained for 0.04 Pr modified BCZT ceramic. Further, a large remnant polarization (2P_r ~ 13 µC/cm²) and low coercive field (E_C ~ 22 V/cm) were obtained for BCZT – 0.04 Pr ceramic. The crystal structure and microstructure affect the photoluminescence and ferroelectric properties. Such properties of 0.04 Pr modified BCZT ceramic make it the potential candidate for novel integrated and multifunctional devices.     

Influence of whey protein concentrate, additives, their combinations on the quality and microstructure of vermicelli made from Indian T. Durum wheat variety

Effect of whey protein concentrate (5%, 7.5%, 10%) and additives on the quality of vermicelli made from Indian durum wheat was studied. The results revealed that with increase in whey protein concentrate (WPC) from 0% to 10%, cooked vermicelli weight increased from 82.5 to 88 g/25 g, cooking loss increased from 6.0 to 8.4%, L values indicating lightness increased (47.42–52.9); b values indicating yellowness decreased (7.0–3.80) and shear force decreased (66–45 g). Sensory evaluation of vermicelli with 5%, 7.5%, 10% WPC showed that addition of above 5% WPC resulted in whitish colour vermicelli with mashy strand quality and sticky mouthfeel. Studies on the effect of additives namely ascorbic acid (0.01% and 0.015%), gluten (1.5% and 3.0%) and glycerol monostearate (GMS) (0.25% and 0.5%) individually as well as in combination on the quality of vermicelli with 5% WPC indicated that combination of 0.01% ascorbic acid, 3% gluten and 0.5% GMS resulted in vermicelli having lower cooking loss, creamy yellow colour, firm, discrete strands and non-sticky mouthfeel. The protein content of vermicelli with 5% WPC and combination of additives was 16% as against 11.5% of control vermicelli. Scanning electron microscopy study of control vermicelli, vermicelli with 5% WPC and vermicelli with 5% WPC and combination of additives revealed that vermicelli with 5% WPC showed a rough surface with a prominent rupture while vermicelli with 5% WPC and combination of additives showed a continuous, rupture free structure.