EFFECT OF HYDROCOLLOIDS ON RHEOLOGICAL, MICROSTRUCTURAL AND QUALITY CHARACTERISTICS OF PAROTTA – AN UNLEAVENED INDIAN FLAT BREAD

The effect of hydrocolloids – namely Arabic (AR), guar (GR), xanthan (XN), carrageenan (CG) and hydroxypropylmethylcellulose (HPMC) – on the rheological, microstructural and quality characteristics of south Indian parotta was studied separately at the level of 0.5%. Addition of hydrocolloids increased farinograph water absorption. The extensograph resistance to extension at 135 min increased with the addition of hydrocolloids. Addition of XN, GR and CG decreased extensibility, while AR and HPMC increased extensibility. The alveograph maximum over pressure increased, with the exception of AR, and average abscissa at rupture decreased with different hydrocolloids. The amylograph peak viscosity increased with all the hydrocolloids. In the micrographs of dough treated with different hydrocolloids, the starch granules appeared coated with gum, and the coating appeared prominent in the case of dough treated with GR and HPMC. Among the hydrocolloids tried, GR brought about the greatest improvement in the quality of parotta, followed in decreasing order by HPMC, XN, CG and AR.

PRACTICAL APPLICATIONS

In India, demand for the large-scale manufacture of packed parottas is increasing. The beneficial effects of hydrocolloids in parotta-making have not yet been explored. This paper discusses the effect of different hydrocolloids on the rheological characteristics of dough in relation to parotta. The information generated on the use of hydrocolloids that are beneficial for parotta-making will be useful for the large-scale manufacturers of parotta.     

MICROWAVE AND CONVENTIONAL BLANCHING EFFECTS ON CHEMICAL, SENSORY, AND COLOR CHARACTERISTICS OF FROZEN BROCCOLI

Broccoli (cv. Empress) obtained from a local supplier was blanched within 15 h of harvest. It was blanched by four methods in covered containers: conventional boiling water (1900 mL, 4 min) (BW), steam (300 mL water, 4 min) (ST), microwave heated in 1 L glass containers (60 ml water, 4 min, 700 W) (MW), and microwave heated in 1 L Seal-a-Meal^TM bags (45 ml water, 4 min) (MWB). Aliquots were frozen at -18C for 4 weeks. Fresh unblanched broccoli peroxidase activity ranged from 389 to 829 units/min; activity was essentially zero immediately after all blanching treatments. The highest reduced ascorbic acid (RAA) content occurred in fresh unblanched broccoli. Some peroxidase regeneration occurred during frozen storage. Immediately after blanching, all blanched broccoli had lower RAA content than control broccoli. MW-blanched broccoli retained the greatest amount of RAA and had appearance, visual color, texture scores, and chroma of florets and stems equivalent to ST-blanched broccoli. MW-blanched broccoli had flavor and general acceptability scores similar to BW-blanched broccoli. After 4 weeks in frozen storage, MW-blanched broccoli had the highest RAA content.     

Image-based determination of chord lengths in air-dried lungs

An image-based method was developed in order to determine chord lengths in sections of dog and sheep lungs air-dried at 25 cm H₂O transpulmonary pressure. To facilitate image processing, optical contrast in the sections was optimized with respect to section thickness, stain type, stain concentration, staining temperature, staining time and clearing method. Digital processing of images used standard procedures, e.g. thresholding, dilation and thinning, as well as algorithms written to subtract background, delete spots and measure chord lengths. Correlation of image-based vs. manual determination of mean chord length in 17 sections from a sheep lung, stained for optimal contrast yielded an R² of 0.82 (P < 0.0001). For 95 sections from three dog lungs, stained with lower contrast, R² was 0.65 (P < 0.0001). Weaker correlations were observed between image-based and manual determinations of the standard deviation, the geometric standard deviation, and the 95th percentile of chord lengths (P < 0.05). The results show that image-based stereology of inflated air-dried lungs can provide valid measures of mean chord length and other statistics of chord length distribution.     

PHYSICAL, CHEMICAL AND SENSORY QUALITY OF MICROWAVE-BLANCHED SNOW PEAS

Snow peas were blanched using four methods [conventional boiling water (BW); steam (ST); microwave (MW); and microwave blanched in heat sealable bags (MWB)], then held frozen at (～18C) for four weeks. Immediately after blanching, MWB‐blanched snow peas retained more reduced ascorbic acid (RAA; 72%), than other treatments. Blanching treatment had no effect on lightness [L* value). With the exception of BW‐blanched peas, blanching significantly altered color. After frozen storage, MWB‐ and MW‐blanched samples both contained about 26 mg/100 g RAA, significantly more RAA than other treatments. MWB‐blanched peas generally had as high or higher sensory appearance, aroma, flavor, texture and general acceptability scores than other treatments. These results imply that blanching snow peas in a heat‐sealable microwave bag, prior to frozen storage, produces a product of equivalent sensory quality and superior nutritional quality compared with more conventional blanching methods.     

A Brief Study on the Ignition of the Non-Thermal Atmospheric Pressure Plasma Jet from a Double Dielectric Barrier Configured Plasma Pencil

To understand the self sustained propagation of the plasma jet/bullet in air under atmospheric pressure, the ignition of the plasma jet/bullet, the plasma jet/bullet ignition point in the plasma pencil, the formation time and the formation criteria from a dielectric barrier configured plasma pencil were investigated in this study. The results were confirmed by comparing these results with the plasma jet ignition process in the plasma pencil without a dielectric barrier. Electrical, optical, and imaging techniques were used to study the formation of the plasma jet from the ignition of discharge in a double dielectric barrier configured plasma pencil. The investigation results show that the plasma jet forms at the outlet of the plasma pencil as a donut shaped discharge front because of the electric field line along the outlet’s surface. It is shown that the required time for the formation of the plasma jet changes with the input voltage of the discharge. The input power calculation for the gap discharge and for the whole system shows that 56% of the average input power is used by the first gap discharge. The estimated electron density inside the gap discharge is in the order of 1011cm-3 . If helium is used as a feeding gas, a minimum 1.48×10-8C charge is required per pulse in the gap discharge to generate a plasma jet.     

Synthesis and characterization of MoO 3 –WO 3 composite thin films by liquid phase deposition technique: Investigation of its photochromic properties

In order to achieve high colouration efficiency, MoO ₃ –WO ₃ composite thin films have been successfully deposited on sodium silicate glass and silicon wafer (111) at 30  $^{\boldsymbol{\circ}}$ C by a very simple novel wet process known as liquid phase deposition. The deposited films were annealed at different temperatures and characterized by carrying out SEM, EDAX, UV-vis and XRD analyses. The EDAX and SEM analyses support the structure and existence of peaks corresponding to Mo, W and O. X-ray diffraction studies showed that MoO ₃ –WO ₃ is amorphous at lower temperature and turns crystalline at higher annealing temperature and suggested the mixture of two crystalline phases such as orthorhombic–monoclinic. Photochromic properties of the MoO ₃ –WO ₃ composite films were studied in the spectral region 400–1200 nm by illuminating them in polychromatic light. The photochromic behaviour is observed to be more effective in composites films in visible region.     

EFFECT OF MICROWAVE POWER LEVEL AND TIME ON ASCORBIC ACID CONTENT, PEROXIDASE ACTIVITY AND COLOR OF SELECTED VEGETABLES

The objective of these studies was to evaluate the effects of blanching at various microwave power levels (30%, 55%, 70%, 100%) for times (0, 1, 2, 3, 4 min) on peroxidase inactivation, and ascorbic acid and color preservation in broccoli, green beans and asparagus. As power level and time increased, moisture losses increased. Actual ascorbic acid concentration (mg/100 g) increased, but when adjusted for moisture loss, it decreased. Microwave treatment at any power level for as little as 1 min reduced peroxidase activity. However, at higher powers (70% and 100%), less time was required to achieve the maximum reduction. Microwave heating at 70% or 100% caused some darkening (decreased L* value). Hue angle decreased (less green) at 55 %, 70% and 100% power after 1 min of treatment. Overall, microwave power level and time had greater effects on moisture, RAA content and on peroxidase activity than on color.