Study on the evaluation method of cigarette astringency in the simulated oral environment.

Cigarettes with pronounced astringency can diminish consumers' enjoyment. However, due to the complex composition of cigarettes, quantifying astringency intensity accurately has been challenging. To address this, research was conducted to develop a method for assessing astringency intensity in a simulated oral environment. The astringency intensity of four cigarette brands was determined using the standard sensory evaluation method. The mainstream smoke absorbing solution (MS) was prepared by simulating the cigarette smoking process, and its physicochemical properties (such as total phenol content and pH levels) were analyzed. The lubrication properties of the five solutions were tested using the MFT-5000 wear tester, and factors influencing cigarette astringency were examined. The findings showed that total phenol content and pH of MS were positively and negatively correlated with astringency intensity, respectively. Particularly, the lubrication properties of MS were significantly correlated with astringency intensity, and the correlation coefficient was affected by load and speed during testing. The study concluded that coefficient of friction was a more reliable measure for assessing the extent of astringency in cigarettes than the total phenol content and pH of MS, offering new insights into astringency evaluation and development of high-grade cigarettes.

Preparation and Properties of PDMS Surface Coating for Ultra-Low Friction Characteristics.

Polydimethylsiloxane (PDMS) has excellent physical-chemical properties and good biocompatibility. Thus, PDMS has been widely applied in biomedical applications. However, the low surface free energy and surface hydrophobicity of PDMS can easily lead to adverse symptoms, such as tissue damage and ulceration, during medical treatment. Therefore, the construction of a hydrophilic low-friction surface on the PDMS surface could be helpful for alleviating patient discomfort and would be of great significance for broadening the application of PDMS in the field of interventional medical catheters. Existing surface modification methods such as hydrogel coatings and chemical grafting suffer from several deficiencies including uncontrollable thickness, surface fragility, and low surface strength. In this study, a hydrophilic surface with ultra-low friction properties was prepared on the surface of PDMS by an ultraviolet light (UV) curing method. The monomer acrylamide (AM) was induced by a photoinitiator to form a coating on the surface of the silicone rubber by in situ polymerization. The surface roughness of the as-prepared coatings was regulated by adding different concentrations of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to the monomer solution, and the coating properties were systematically characterized. The results indicated that the roughness and thickness of the as-prepared coatings decreased with increasing AMPS concentration and the as-prepared coatings had good hydrophilicity and low-friction properties. The Coefficient of Friction (CoF) was as low as 0.0075 in the deionized water solution, which was 99.7% lower than that of the unmodified PDMS surface. Moreover, the coating with a lower surface roughness exhibited better low-friction properties. The results reported herein provide new insight into the preparation of hydrophilic, low-friction coatings on polymer surfaces.

Fractional derivative modeling for characterizing stress relaxation properties of Hami melon during drying.

The viscoelastic properties of food materials will change significantly while drying is in progress, which greatly influences the food deformation caused by drying. This study aims to predict the viscoelastic mechanical behavior of Hami melon during drying using the fractional derivative model. To characterize the relaxation characteristics, based on the finite difference method, an improved Grünwald-Letnikov fractional stress relaxation model is proposed to derive an approximate discrete numerical solution of the relaxation modulus by applying the time fractional calculus. The Laplace transform method is used to verify the obtained results, and the equivalence of the two methods is proved. In addition, the stress relaxation tests prove that the fractional derivative model has a better prediction effect on the stress relaxation behavior of viscoelastic food than classical Zener model. The significant correlations between the fractional order and the stiffness coefficient and the moisture content is also studied. Which is negative correlation and positive correlation respectively.

Effect of Sugar and Milk Powder Addition on the Mechanical Properties and Texture of Chocolate.

In order to investigate how the addition of two common ingredients in chocolate, sugar and milk powder, affects the mechanical properties of solid chocolate, uniaxial compression tests and wedge fracture tests were carried out using four ratios of chocolate as the experimental material. Mechanical properties such as Young's modulus and fracture toughness were directly correlated with textural properties such as hardness, elasticity, and brittleness. The results show that adding sugar increases Young's modulus and fracture toughness of chocolate, while milk powder is the opposite. In equal amounts of both, sugar played a more substantial role. In combination with the properties exhibited by chocolate in the above tests, data from creep tests were collected to improve the classical Bingham model and develop a new constitutive model for predicting the mechanical behaviour of solid chocolate with different ratios of added sugar and milk powder. The new four-component constitutive model allows for a more accurate fit to the creep test data and this work provides some suggestions for making different tasting chocolates by adjusting the addition of ingredients.

Fabrication and Characterization of Polyelectrolyte Coatings by Polymerization and Co-Deposition of Acrylic Acid Using the Dopamine in Weak Acid Solution.

Existing medical materials (such as silicone rubber, glass slides, etc.) fail to meet the functional requirements of biosensing, cell culture, and drug delivery due to their poor wettability. The preparation of polyelectrolyte coatings with excellent wettability and protein adsorption helps broaden the application of medical materials. Poly(acrylic acid) (PAA) is a common polyelectrolyte with stronger protein adsorption, but the existing methods for obtaining PAA coating have certain shortcomings to limit their industrial applications. In this study, dopamine (DA) was used to polymerize and co-deposit acrylic acid (AA) in weak acid solution to functionalize the surface of materials, and the effects of different mass ratios of DA/AA on the wettability and protein adsorption of the coating were deeply investigated. The results demonstrate that PDA/PAA coating is successfully prepared on the surface of four substrates and greatly reduces the water contact angle of these surfaces. Moreover, these coatings show excellent protein adsorption, and the amount of adsorbed protein on the coated QCM chip is increased by 57.74% than the uncoated QCM chip. In addition, the coating has a certain pH responsiveness, and its wettability and protein adsorption are closely related to the pH of the solution. The preparation strategy proposed is simple and substrate-independent, which provides valuable insights into the application of the one-step polymerization and co-deposition strategy under weak acid conditions.

Bionic design of the oral swallowing in vitro and its application in the dysphagia.

Dysphagia, the swallowing disorder, is a common disease among the elders and stroke patients. Therefore, based on the bionic swallowing device (BSD) in vitro of similar human-tongue motion during swallowing, the development of functional food is necessary to improve the food swallowing quality of the deglutition disorders patients. In this study, the tongue motion was thoroughly investigated by extracting the characteristic data, and appropriate mechanisms in vitro were adopted to replicate the motion of the tongue swallowing according to the normal swallowing oropharyngeal data. The application of the BSD was also investigated at different swallowing grades (SGs). The study results indicated that the tongue motion consisted of tongue root point (TRP) and several tongue motor points (TMPs). The cam-link and push-rod mechanisms showed ellipse lines for TRP motion and straight lines for TMPs, respectively. Higher correlation coefficients between the tongue trajectories in the oropharyngeal data and simulated curves of the combined mechanism were observed. The average correlation coefficients between the tongue trajectories of patients at five SGs and those of the BSD were 0.87, proving its effectiveness and potential application. Furthermore, the corn-paste experiments of the BSD showed that dysphagia at five SGs could be a suitable choice for certain food concentrations. This will provide valuable insight into developing more functional foods in vitro for high deglutition disorders.

Fabrication of a Hydrophilic Low-Friction Poly(hydroxyethyl methacrylate) Coating on Silicon Rubber.

Silicon rubber has been widely used in the biomedical field due to its excellent mechanical properties and physiological inertia. However, the hydrophobic properties of silicon rubber surfaces limit their further application. Therefore, constructing a silicon rubber coating with hydrophilic and low-friction surface properties would be highly significant. Existing methods to achieve such coatings, including grafting polymer brushes and the deposition of hydrophilic materials, suffer from several deficiencies such as complicated coating processes and insufficient coating firmness. In this paper, we report a hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) coating that can easily coat the surface of silicon rubber to provide low-friction performance. Sample silicon rubber was treated with benzophenone and hydroxyethyl methacrylate monomer solution in turn. The as-prepared coating was characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, white light interference, and MFT-5000 wear test. The results indicated that the PHEMA coating had excellent hydrophilic properties (with a low contact angle of 9.39°) compared to uncoated silicon rubber. As the concentration of glycerol in the monomer solution was increased, the thickness and surface roughness of the as-prepared coating gradually decreased. The coating was firmly adsorbed on the substrate, and it had a zero-class bonding strength. In addition, the as-prepared coating demonstrated good friction-reduced properties, with the coefficient of friction being reduced by 98.0% compared with the uncoated silicon rubber in simulated blood. In summary, a hydrophilic and low-friction coating was successfully prepared using a simple method, and the results reported herein provide valuable insight into the surface design of similar soft materials.

A rapid method to evaluate the chocolate smoothness based on the tribological measurement.

Cocoa is the primary ingredient in chocolate, and cocoa concentration attributes to the smoothness of the chocolate. Supporting this statement, we assessed the smoothness and melting properties of five chocolates of different cocoa concentration from three brands using the professional sensor evaluation and weight method, respectively. Artificial saliva was added to obtain the mixed chocolate solutions, and their viscosity and coefficient of friction (CoF) were measured for three rubbing pairs. The correlation of chocolate smoothness with their viscosities and average CoF (aCoF) was also discussed. The results indicated that the cocoa concentration significantly affected the smoothness of the chocolates among the three brands. The mixed solution of 50% chocolate could be a representative of oral processing, but their viscosities were not proficient enough to effectively characterize their smoothness. The aCoF of 50% chocolate solution could be rapid and effective to evaluate their smoothness. In addition, the Two-GCTPE rubbing pair was more suitable way to evaluate the smoothness of similar foods in the oral environment. The study results will provide a better insight into characterizing certain attribution of similar foods.

Investigation of contact characteristics and frictional properties of natural articular cartilage at two different surface configurations.

Natural cartilage surfaces were macroscopically curved with multi-porous viscoelastic biologic materials with extremely high water, but whether curved surface configuration could play an important role on the contact and frictional properties of natural cartilages fails to be completely understood up to now. In this current study, cartilage samples came from the 18-24 month-old bovine femora. Contact characteristic and frictional properties at two cartilage configurations were investigated using the UMT-2 testing rig and the five-point sliding average method would be adopted to analyze these tested data. These results indicated the surface displacement was extremely associated with the plate cartilage surface and seemed to be a representative of cartilage surface configuration. The summit of the surface load lagged behind that of the surface displacement at the same condition. Coefficient of friction showed obviously different variation with time at two cartilage surface configurations due to the fact that these two surface displacements had different amplitudes and opposite directions as a function of the sliding length. Therefore, surface configuration played the main role on these variables of contact displacement, contact load and coefficient of friction due to the direction and magnitude of the surface displacement while applied load and sliding velocity had a secondary role. Natural cartilage surfaces were macroscopically curved with multi-porous viscoelastic biologic materials with extremely high water, but whether curved surface configuration could play an important role on the contact and frictional properties of natural cartilages fails to be completely understood up to now. In this study, two different cartilage configurations were adopted to investigate natural cartilage properties, and the five-point sliding average method would be used to analyze these tested data. These results indicated the contact displacement was consisted of cartilage deformation and surface displacement while contact load was composed of steady load and surface load (as shown in the figure, panels (a) and (b)). Surface displacement was greatly associated with the plate cartilage surface and seemed to be a representative of cartilage surface configuration. These two surface displacements had different amplitudes and opposite directions as a function of the sliding length (as shown in panel (c)). The summit of the surface load lagged behind that of the surface displacement at the same condition (as shown in panel (d)). Surface displacement and surface load in the contact characteristic of natural cartilages were extremely related with the cartilage configurations. and their correlation coefficients varied periodically with the moving time (as shown in panel (e)). Coefficient of friction showed obviously different variation with time (as shown in panel (f)). Therefore, surface configuration played the main role on these variables of contact displacement, contact load and coefficient of friction due to the direction and magnitude of the surface displacement while applied load and sliding velocity had a secondary role. Variation in contact and frictional properties of natural cartilage at two different surface configurations (a) Contact displacement and its parts varied with time; (b) Contact load and its parts varied with time;