Physical characterization of low-calorie chocolate formulations

Development of a high-quality low-calorie chocolate needs the use of the most appropriate ingredients that could substitute sugar without negatively affecting several product properties. In this study, sucrose-reduced chocolates sweetened with sucralose and stevia by using bulking agents were investigated in relation to their rheological, textural and sensory attributes. Dark, milk and white chocolates with different amounts of sweeteners were formulated. The Casson model best fitted to the rheological data. In dark chocolates, partial substitution of sucrose with stevia (DCSSt) gave similar plastic viscosity and yield stress values with control samples (DCS). Hardness measurements also supported these results. DCSSt sample was again found to be very similar to control in tested sensory attributes when assessed by a consumer panel. The data indicated that it was possible to manufacture chocolate by partial replacement of sucrose with stevia without adversely affecting its important rheological, textural properties and sensory acceptance.     

Physiological changes of Escherichia coli O157:H7 and Staphylococcus aureus following exposure to high hydrostatic pressure

Morphological changes and membrane integrity of Escherichia coli O157:H7 and Staphylococcus aureus cells before and after high hydrostatic pressure (HHP) treatments (200–400 MPa) and time (1–5 min), at a constant temperature (40 °C), in peptone water were examined by using scanning electron microscopy (SEM) and fluorescent microscopy, respectively. SEM images showed that unpressurized cells exhibited a smooth surface appearance. E. coli O157:H7 cells exposed to pressure treatments first appeared larger, then with increasing pressure distorted with dimples and pinches. In case of S. aureus, the cells pressurized at low pressure levels did not show any significant change. The surface appearance became rough and cracked when the cells were exposed to higher pressure levels. Images of fluorescent microscopy showed that a small proportion of bacterial cells were not green fluorescent at lower pressure levels. The other part of the cell population was red fluorescent representing dead cells and the number of red fluorescent cells increased with increasing pressure. The cells with a yellowish color showed that varying levels of membrane damage occurred under HHP. The combinations of mild heat, antimicrobial substances and HHP treatment can be used to inactivate food borne pathogens of varying pressure resistance in the food industry for safe processing conditions. However, the resultant damaged cells at different levels should be taken into account during storage to prevent their recovery.     

The behavior of chemical and electrochemical Ag deposition on FeNi‐mesh cathodes in Al‐air battery

In this study, FeNi/Ag cathode was made for aluminium air battery. For this purpose, FeNi‐mesh electrode surfaces were treated in two different ways (chemical and electrochemical deposition), with noble metal silver having a high catalytic activity. The optimum time for both methods was determined. The electrochemical properties were determined using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and current‐potential (i‐t) curves. The battery performance tests were performed, and surface characteristics of the electrodes were determined with a scanning electron microscope an X‐ray diffraction method (SEM‐EDS and XRD). This study shows that FeNi mesh electrodes chemically and electrochemically deposited with silver are alternative for oxygen‐reducing cathodes for aluminium air battery because they are cheap, practical, and effective. The electrochemical (FeNi/Ag‐ED) deposition is better than the chemical (FeNi/Ag‐CD) deposition in terms of both economical and higher battery potential.     

Thermal decomposition behavior of tobacco stem Part I: TGA–FTIR–MS analysis

In the present study, the thermal degradation behavior of tobacco stem was examined by means of a thermogravimetric analyzer (TGA) under nitrogen atmosphere at temperature range of 25–1,000°C. The TG curve indicated that the pyrolysis process of tobacco included three zones, and main pyrolysis occurred in the second zone by means of the decomposition of hemicellulose, cellulose, and lignin in a temperature range of 180–540°C. Furthermore, the gases evolved during the degradation were analyzed simultaneously via TGA coupled with a Fourier transform infrared spectrometer (FTIR) and mass spectrometer (MS). Carbon dioxide, methane, water, formaldehyde, and propanal were the main volatiles detected via MS and confirmed by FTIR.     

Thermal decomposition behavior of tobacco stem Part II: Kinetic analysis

As a continuation of the previous study on the thermal degradation behavior of tobacco stem, this work is focused on the kinetics of pyrolytic decomposition. Thermogravimetric analysis of tobacco stem samples was conducted under nitrogen atmosphere at different heating rates of 5, 10, 15, and 20°C/min at a temperature range of 25–1,000°C. The kinetic parameters, such as activation energy, pre-exponential factor, and reaction order, were determined by applying the Coats–Redfern method for the main pyrolysis occurred in the second zone by means of the decomposition of hemicellulose, cellulose, and lignin at a temperature range 180–540°C. In addition, the activation energy was calculated using various degradation models, including Kissinger, Friedman (FR), Flynn–Wall–Ozawa (FWO), and Kissinger–Akahira–Sunose (KAS). The average activation energy of tobacco stem was calculated to be 150.40, 230.76, 216.97, and 218.56 kJ/mol by the Kissinger, FR, FWO, and KAS models, respectively.     

Zirconia ceramic fixed partial dentures after cyclic fatigue tests and clinical evaluation: a systematic review

ABSTRACT

Zirconia fixed prosthetic dentures are extensively used for replacing missing teeth. The primary objective of this systematic review was to gather and present the results of all in vitro studies and clinical trials conducted on zirconia fixed prosthetic dentures. This review concentrated exclusively on bilayered zirconia and monolithic fixed prosthetic dentures. As such this paper can act as a guideline for more comparable future experimental work on zirconia ceramics. Future studies must use a more systematic approach such as the uniform use of abutment material, material for simulating periodontal support, data about fracture strength before and after fatigue, number of cycles, information about position and size of the indenter. The new digital techniques with long-term follow-up are desirable in further clinical studies.     

Effects of chemical and physico-chemical surface conditioning methods on the adhesion of resin composite to different mineral trioxide aggregate based cements

This study investigated the adhesion of resin composite to mineral trioxide aggregate based cements after different chemical and physico-chemical surface conditioning methods. Mineral trioxide aggregate based cements (Biodentine, ProRoot MTA, Imicryl MTA) were embedded in Teflon disks (N?=?180). After storing at 37?°C at 100% humidity for 72?h, substrate surfaces were polished using silicon carbide papers. Specimens were allocated to 3 groups to be conditioned with one of the following (n?=?15 per group): a) Adhesive resin (Clearfil SE Bond, CSE), b) Adhesive resin (Adper Single Bond 2, SB2), c) air-abrasion with 30?μm alumina coated with silica?+?silane?+?adhesive resin (ALB), d) no surface conditioning, control group (CON). Microhybrid resin composite (Filtek Z250) was applied on the conditioned substrate surfaces and photo-polymerized. After storage at 37?°C at 100% humidity for 24?h, adhesive interfaces were loaded under shear (1?mm/min) in a universal testing machine. After debonding failure types were analyzed. Data were analyzed using 2-way ANOVA and Tukey’s test (alpha = 0.05). SBS results were significantly affected by surface conditioning (p?<?0.05) and materials (p?<?0.05). Interaction terms were significant (p?<?0.05). Biodentine-ALB resulted in significantly higher SBS values (3.96?±?1.24) compared to those of other combinations, while ALB and SB2 resulted in no significant difference for ProRoot MTA and Imicryl MTA (p?>?.05). CSE (1.36?±?0.5- 1.98?±?0.76) did not significantly increase SBS for all MTA materials compared to the control group (0.8?±?0.52 – 2?±?0.91) (p?>?9.05). While CON groups resulted in exclusively adhesive failures, ALB presented the highest incidence of mixed failures for all materials tested (60–100%).     

Intraoral repair of chipped or fractured veneered zirconia crowns and fixed dental prosthesis: clinical guidelines based on literature review

This article aimed to review the susceptibility to chipping, influencing factors, current protocols for intraoral repair and provide the clinicians with guidelines for repairing. Peer-reviewed literature in English published between 01/01/2000 and 30/06/2017 was electronically searched using PubMed and Google Scholar, followed by manual search of the scientific literature. Multiple key words and their combinations (‘Zirconium’, ‘Zirconia’, ‘Intraoral’, ‘Repair’, ‘Chipping’, ‘Fracture’, ‘Bonding’, and ‘Surface treatment’) and different search strategies were employed for sample selection. The initial search resulted in 189 articles, of which 98 were included in this review. The chipping rates of veneered zirconia-based restorations have been reported range between 0 and 44%. Researchers and clinicians were in favor of the intraoral repair of chipped veneered zirconia-based restorations. While various intraoral repair protocols were available based on the severity of chipping, decisions about intraoral repair were based on the clinical situation, availability/accessibility of repair kits, survival/success rate of repairing, and patient concerns. Intraoral repair seems to be a promising option to correct moderate size of chipping, and its success largely depends on the surface treatment methods used for the fractured surfaces. Hydrofluoric acid etching of the veneering porcelain followed by silanization and air-abrasion of the zirconia framework and then MDP priming have been recommended to create durable bonds. This review suggests that intraoral repair of chipped zirconia-based restorations offers a satisfying option for the patient when restoration replacement is not an option. Treatments for the fracture surface are the most important factors influencing the longevity of repaired zirconia-based restorations.