One-year bonding performance of one-bottle etch-and-rinse adhesives to dentin at different moisture conditions

Abstract

This study aimed to investigate the one-year bond strengths to dentin of one-bottle etch-and-rinse adhesive systems applied under different moisture conditions. Class V cavities were prepared in bovine incisors and randomly allocated (n?=?8) according to the type of adhesive system used – SB (Adper? Single Bond 2); PB (Prime & Bond 2.1); and XPB (XP Bond) – and the moisture condition kept in the cavity – moist, over-wet, and over-dry. Filtek? Z250 was used for teeth restoration. Specimens for microtensile bond strength (µTBS) test were obtained and stored in water for 24?h or 1?year, and submitted to mechanical testing. Data were analyzed using t-tests, ANOVA and the Holm–Sidak post hoc test (α?=?0.05). Weibull analysis was used to verify the reliability of specimens. The type of adhesive and the moisture condition of the substrate affected the µTBS. At 24?h, SB performed better under the moist and over-wet conditions. At 1?year, SB, PB, and XPB showed the greatest percentage reduction at the moist (～38%), over-wet (100%), and over-dry (100%) conditions, respectively. The reliability of adhesives was affected by the variable factors tested. In conclusion, the solvent composition of adhesives and the moisture condition of the substrate play an important role in the bond strength and bonding stability of resin-based restorations, as well as on the reliability of the adhesive interfaces over time.     

Current status of biotechnological production and applications of microbial exopolysaccharides

Abstract

Microbial exopolysaccharides (EPS) are an abundant and important group of compounds that can be secreted by bacteria, fungi and algae. The biotechnological production of these substances represents a faster alternative when compared to chemical and plant-derived production with the possibility of using industrial wastes as substrates, a feasible strategy after a comprehensive study of factors that may affect the synthesis by the chosen microorganism and desirable final product. Another possible difficulty could be the extraction and purification methods, a crucial part of the production of microbial polysaccharides, since different methods should be adopted. In this sense, this review aims to present the biotechnological production of microbial exopolysaccharides, exploring the production steps, optimization processes and current applications of these relevant bioproducts.     

PBAT/hybrid nanofillers composites—Part 2: Morphological,thermal and rheological properties

This work is an investigation of the effect of different nanofillers: organically modified montmorillonite (MMT), sepiolite (SEP) and nano titanium dioxide (nTiO₂) and combination of them in poly(butylene adipate-co-terephthalate) (PBAT) films. Thermal morphological and rheological analyses were conducted to explain the behavior of this nanoparticles on O₂ and water vapor permeability coefficients, light transmission, and mechanical properties presented in previous study. Thermal stability of the nanocomposites was slightly decreased by the nanofillers presence. Differential scanning calorimetry and X-ray analyses were carried out to investigate the crystallization behavior of nanocomposites. Transmission electron microscopic analysis showed regular and homogeneous dispersion of the nanoparticles, but scanning electron microscopy showed lack of adhesion in the sepiolite-PBAT interface. Rheological measurements showed significant increase in both complex viscosity and storage modulus due to interactions between clays and PBAT and the effect of sepiolite and nTiO₂ on improving the exfoliation of montmorillonite as synergism between the nanofillers.     

Wasted bread flour as a novel ingredient in cake making

Bread is one of the most wasted products in both industry and retail. This study analysed the use of bread flour of various particle sizes (1000 μm, 500 μm and 200 μm) in different percentages for sponge formulations (10% and 20%) and layer cakes (10%, 20% and 30%). Viscosity, microstructure and density of batters, as well as specific volume, texture and colour of cakes were evaluated. The inclusion of bread flour change batter microstructure. Viscosity does not affect the sponge batters but it tends to increase in the layers, mostly in the case of finer flours. The specific volume is reduced in sponge cakes while hardness is generally increased, even with the lowest percentages of bread flour. In layers, this reduction in volume is only visible at the highest doses of flours below 500 microns with no changes in hardness.     

Viability of Hanseniaspora uvarum yeast preserved by lyophilization and cryopreservation

Hanseniaspora yeasts are known to produce volatile compounds that give fruity aromas in wine and fermented fruit. This study aimed to verify the feasibility of the Hanseniaspora uvarum strain that had been isolated and identified during a previous study and preserved by lyophilization and freezing at ?80 °C (cryopreservation). This strain was assessed in relation to its macroscopic and microscopic morphology and for its ability to ferment apple must. After having been subjected to lyophilization and cryopreservation, viability was assessed in relation to these characteristics during 12 months of storage. The strain showed stable colonial features and its microscopic appearance was unchanged during all recoveries. The plate count results showed consistency in both processes. Regarding the fermentative capacity, the kinetic results showed 100% viability for the strain subjected to lyophilization, as well as for those preserved at ?80 °C. These results demonstrate that the preservation methods used are compatible with the maintenance of the relevant characteristics of the strain for the period of evaluation of this study (12 months). Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of the particle size of pear pomace on the quality of enriched layer and sponge cakes

Pear pomace (PP) is a by-product of the fruit industry with a high content of fibre. Its potential as an ingredient at 15% or 30% level for sponge and layer cakes was investigated. Three PP powders with different particle sizes (fine, medium and coarse) were obtained. Batter microstructure, density and viscosity and cake specific volume, texture and colour were evaluated. When PP was added, less uniformity in bubble distribution was observed in batters, particularly at higher particle sizes. Cake specific volume significantly diminished with increasing amounts of PP. For sponge cakes, the decrease in specific volume was the highest for the finest particle size of PP. In general, increasing PP addition increased hardness and reduced elasticity, cohesiveness and resilience but the effect depended on the particle size. In general, better textural attributes were obtained with medium and coarse particle sizes. These results indicate that PP of an adequate particle size could be a promising fibre source for different cake formulations.     

Isolation,identification and development of culture medium in the production of Chlorella vulgaris

Microalgae have gained importance as a potential component of conventional food. The aim of the present study was to study the behaviour of the microalga Chlorella vulgaris in relation to the different carbon and nitrogen sources and to improve a culture medium in terms of glucose, urea, manganese chloride and sodium nitrate concentrations. In the investigation of the best source of carbon and nitrogen, it was observed that 1.14 mg L^?1 of glucose and 8.32 mg L^?1 of urea stood out with the production of 0.823 g L^?1 of dry biomass and yield of 52 mg L^?1 day^?1. The best growth rate and specific yield were achieved at the central points for all salts.     

Critical points of Brazil nuts: a beginning for food safety,quality control and Amazon sustainability

BACKGROUND: One difficulty of self‐sustainability is the quality assurance of native products. This research was designed to study the risks and critical control points in the collection, handling and marketing of Brazil nuts from native forests and urban fairs in the Brazilian Amazon by characterisation of morphological aspects of fungi and posterior identification by molecular biology and determination of aflatoxins by high‐performance liquid chromatography. RESULTS: Several corrective actions to improve product quality were found to be necessary in both sites. Growth of fungi was observed in 95% of fragments of Brazil nuts from both sites during the between‐harvest period. Aflatoxin levels indicated that, although fungal growth was observed in both sites, only Brazil nuts from the native forest showed a high risk to human health (total aflatoxin level of 471.69 µg kg^?1). CONCLUSION: This study has shown the main issues related to the process design of Brazil nuts, supporting the necessity for research on new strategies to improve the quality of nuts. Also, the habit of eating Brazil nuts stored throughout the year may represent a risk to farmers. © 2012 Society of Chemical Industry     

Gluten‐Free Breads: The Gap Between Research and Commercial Reality

The market for gluten‐free products is steadily growing and gluten‐free bread (GFB) keeps on being one of the most challenging products to develop. Although numerous research studies have worked on improving the manufacture of GFBs, some have adopted approaches far from commercial reality. This review analyzes the ingredient list and nutrition facts of 228 commercially available GFBs produced by different brands around the world. The results from studying the ingredient list of breads revealed that commercial breads do not tend to use a single starchy source or gluten replacer, but a combination of several ingredients to optimize bread quality. Maize, tuber starches, and rice flour were the main starchy sources. Regarding hydrocolloids, the most often included ingredients were hydroxypropyl methylcellulose, xanthan and guar gum, and psyllium. Proteins and sugars were added, respectively, in 81% and 87% of the commercial breads analyzed. Furthermore, it was found that vegetable oils were preferred over fats. A long list of ingredients was observed in commercial GFBs, with the presence of a wide range of additives, including acidifiers, emulsifiers, leavening agents, preservatives, and aromas or flavorings. Meanwhile, nutrition facts showed a lower protein and higher fat content for GFBs compared to a gluten‐containing counterpart, with small differences for salt and sugar. This research expands the current knowledge on GFB manufacturing, giving a panoramic outlook on the current situation in the GFB market, and helping both scientists and gluten‐free companies unify/identify common trends.