Dielectric properties of LiF single crystals

The dielectric constant,, loss, tan, and a.C. Conductivity, , of high quality single crystals of LiF have been measured in the frequency range 10² to 10⁵ Hz and in the temperature range 30 to 400° C. of LiF at 30° C is 8.3 and is frequency independent; tan was below detection level (tan<0.0001). increases slowly with temperature up to about 150° C (frequency independent region) beyond which it rises rapidly, being frequency dependent with larger values at lower frequencies. A similar behaviour is exhibited by tan . The activation energy for conduction in the high temperature region is calculated to be 0.93 eV from log against 1/T graphs. Log () against 1/T plots (where is the difference between the dielectric constant at any temperature and the value at room temperature, 30° C) yields an activation energy value of 1.0 eV in the high temperature region. This activation energy is found to be independent of frequency. This agreement between the two activation energy values, one for the a.c. conductivity and the other for the increase with temperature. This suggests that the same charge carriers are responsible for the two processes in the high temperature region.     

Insulating and Other Physical Properties of CoO‐Doped Zinc Oxyfluoride‐Borate Glass‐Ceramics

Zinc oxy fluoro borate glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) are synthesized and subsequently crystallized. The scanning electron microscopy pictures have exhibited crystallinity. Differential scanning calorimetric studies have indicated that the prepared samples consist of multiple crystal phases. The X‐ray diffraction patterns have indicated that the glass‐ceramic samples are composed of αZn(BO₂)_2, (Zn)₃(BO₃)_2, CoF₂, CoF₃, Co₃FB₇O₁₃, ZnCo₂O₄, Co₃O₄ crystalline phases. The optical absorption and photoluminescence studies have indicated that there is a gradual increase of tetrahedral cobalt ion concentration with increase of CoO concentration in the glass network. IR spectroscopic studies have pointed out increased degree of polymerization of the zinc oxy fluoro borate glass network with increase of CoO content. The analysis of results of dielectric properties indicated increase of insulating strength of the glass‐ceramics with increase of CoO content. Finally, the dielectric breakdown strength of the samples is measured at room temperature in air medium and it is found to increase from 12.9 to 19.2 kV/cm with increase of CoO from 0.2 to 2.0 mol%. The reasons for such increase of breakdown strength are discussed quantitatively in terms of dielectric parameters with aid of data on spectroscopic properties.     

Attachment and biofilm formation of Pseudomonas fluorescens PSD4 isolated from a dairy processing line

The effects of different nutrient sources and temperatures on attachment and biofilm formation of Pseudomonas fluorescens PSD4, a dairy isolate, were studied. Initial adherence and attachment capabilities among different strains were studied using microtitre plate assays. Biofilm development was observed using confocal microscopy. Strongly adherent cells were seen in protein rich media. Citrate as a carbon source enhanced biofilm formation. Glucose did not favor biofilm development. Psychrotrophic P. fluorescens PSD4 formed strongly adherent biofilms having high metabolic activities at low temperatures. P. fluorescens PSD4 with spoilage potential was capable of forming strong biofilms in dairy processing environments. Biofilm formation was influenced by nutrient availability and growth conditions. These factors should be considered for design of effective anti-biofilm strategies.     

Effect of stabilisation treatment of rice bran on functional properties of protein concentrates

The functional properties of differently dried protein concentrates prepared from unstabilised, acid-stabilised, heat-stabilised and parboiled rice bran were evaluated. Freeze-dried protein concentrates from all types of bran exhibited similar nitrogen solubilities. Both cabinet-and roller-dried protein concentrates had lower nitrogen solubilities than freeze-dried samples except for cabinet-dried concentrate from heat-stabilised bran. The functional properties (bulk density, water and fat absorption, emulsification and foaming capacity) of protein concentrates prepared from acid-stabilised rice bran were not significantly different from those prepared from untreated bran. Freeze-dried protein concentrates from both heat-stabilised and parboiled rice bran had low water absorption capacity and high fat absorption capacity. Cabinet-dried samples did not exhibit any foaming or emulsification capacity, thereby indicating a greater extent of denaturation. Thus, the study indicated that in addition to stabilisation treatment functionality was also influenced by the drying technique employed.     

Effect of soya protein on the dialysability of exogenous iron and zinc

The investigation aimed at studying the influence of soya proteins on in vitro dialysability of exogenous iron and zinc. Soyabean was processed into various components like soya flour (SF), concentrate (SC) and isolate (SI) and two peptides (<30 kDa and >30 kDa). The protein contents of SF, SC and SI were 51, 62 and 78 g/100 g, respectively. Their iron contents ranged between 9.7 and 15.8 mg/100 g and zinc contents from 3.3 to 6.7 mg/100 g. Phytic acid contents (mg/100 g) of the soya components were SF 339, SC 226, SI 186 and peptides 18–20. In SF, percent dialysable iron and zinc were 12.6 and 50, respectively, this reduced to one-third and one-fifth in SC and SI. Dialysability of exogenously added minerals was found to be significantly lower in all soya protein components. However, the inhibitory effect was less pronounced in peptides. The protein component/matrix effect needs to be investigated to counteract the inhibitory effect of soya on iron dialysability.     

Effect of Ingredients on Rheological, Nutritional and Quality Characteristics of High Protein, High Fibre and Low Carbohydrate Bread

Effect of replacement of wheat flour with a combination of soy protein isolate, oat bran and chickpea flour (SPOBCP) at the levels of 20%, 40% and 60% and addition of combination of additives such as fungal ??-amylase, dry gluten powder, sodium stearoyl-2-lactylate, hydroxypropylmethylcellulose (CA) on the rheological and nutritional characteristics of bread was studied. Use of SPOBCP decreased farinograph dough stability, increased pasting temperature, decreased cold paste viscosity and overall quality score of bread. Scanning electron microscopy images showed higher degree of disruption of protein matrix in bread dough with 60% SPOBCP than 20% and 40% SPOBCP. Addition of 60% SPOBCP resulted in flat, uneven shaped bread with an overall quality score of 38 when compared with 54, 81 and 91 for breads with 40%, 20% and 0% SPOBCP, respectively. However, use of CA increased the strength of the dough and improved the overall quality of bread with 40% SPOBCP. Nutritional profile of bread with 40% SPOBCP?+?CA showed higher protein, in vitro protein digestibility, total dietary fibre, resistant starch, ??-glucan and lower starch hydrolysis index than control bread.     

Induced crystallization and physical properties of Li2O–CaF2–P2O5:TiO2 glass system: Part I. Characterization, spectroscopic and elastic properties

Li₂O–CaF₂–P₂O₅ glasses mixed with different concentrations of TiO₂ (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young's modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO₄ and TiO₆ structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6 mol% of TiO₂ possesses the highest density, high mechanical strength and more compact network.     

Bacterial Quorum Sensing and Food Industry

Abstract: Food spoilage and biofilm formation by food‐related bacteria are significant problems in the food industry. Even with the application of modern‐day food preservative techniques, excessive amounts of food are lost due to microbial spoilage. A number of studies have indicated that quorum sensing plays a major role in food spoilage, biofilm formation, and food‐related pathogenesis. Understanding bacterial quorum‐sensing signaling systems can help in controlling the growth of undesirable food‐related bacteria. This review focusses on the various signaling molecules produced by Gram‐negative and Gram‐positive bacteria and the mechanism of their quorum‐sensing systems, types of signaling molecules that have been detected in different food systems using biosensors, the role of signaling molecules in biofilm formation, and significance of biofilms in the food industry. As quorum‐sensing signaling molecules are implicated in food spoilage, based on these molecules potential, quorum‐sensing inhibitors/antagonists can be developed to be used as novel food preservatives for maintaining food integrity and enhancing food safety. Practical Application: Bacteria use signaling molecules for inter‐ and intracellular communication. This phenomenon of bacterial cell‐to‐cell communication is known as quorum sensing. Quorum‐sensing signals are implicated in bacterial pathogenicity and food spoilage. Therefore, blocking the quorum‐sensing signaling molecules in food‐related bacteria may possibly prevent quorum‐sensing‐regulated phenotypes responsible for food spoilage. Quorum‐sensing inhibitors/antagonists could be used as food preservatives to enhance the shelf life and also increase food safety.