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.

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.

Development and validation of a chewing robot for mimicking human food oral processing and producing food bolus.

More and more studies have being done on the deformation process of food and the formation of food bolus during chewing. However, it is hard to observe the food oral processing (FOP) of subjects and obtain related data directly. A bionic chewing robot based on a six-axis parallel mechanism was proposed in this paper. The robot can not only simulate the movement of the lower jaw but also set a variety of oral processing parameters, such as the number and shape of teeth, oral temperature, saliva volume, chewing cycles, speed and force. Meanwhile, dental wax and peanuts were taken as food samples, and the chewing experiments were carried out by the bionic chewing robot and subjects, respectively. The results showed that the bionic chewing robot could be used to mimic human FOP and produce food bolus. Especially when the chewing cycles met the requirement of swallowing, the median particle size of the peanut bolus and the mixing effect index of the dental wax bolus in the two different experiments were highly consistent. In addition, the robot was proved to have the same food texture detection function as the texture analyzer.

Effect of gelatin content and oral processing ability on vitamin C release in gummy jelly.

In order to investigate the factors affecting the release of vitamin C (VC) in gummy jelly during oral processing, four levels of gelatin (3%, 6%, 9% and 12%) were selected and a bionic chewing robot was employed in chewing experiments. Textural profile analysis showed the hardness of gummy jelly increased from 91.7 N to 198.8 N when the gelatin content was raised from 3 to 12%. Single factor chewing experiment showed that the release of VC was positively correlated with chewing frequency (Fchew) and chewing strain (STchew), while negatively correlated with gelatin content, chewing speed (SPchew) and volume of saliva (Vsaliva). Orthogonal chewing experiment showed that the priority of the factors affected the release of VC was following: STchew > Fchew > SPchew > Vsaliva. Multivariate linear regression analysis proposed a model to predict the amount of VC released and the goodness-of-fit of the model was 95.7%. The amount of VC released was the highest under the combination of Fchew 12 times, STchew 100%, Vsaliva 2 ml and SPchew 40 times/min. The optimal amount of gelatin addition was 6%. This study provided an effective reference for the formula design and chewing mode optimization of gummy jelly.

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.

[Study on the synthesis of a new reagent 3-(4'-fluorophenyl)-5-(2'-arsenoxylphenylazo)-rhodanine and the fluoresence determination of bismuth(III)].

A new fluorescence reagent, 3-(4'-fluorophenyl)-5-(2'-arsenoxylphenylazo)-rhodanine, was synthesized. The structure of the reagent was clarified by elemental analysis and IR. At pH 5.4, the reagent can react with trace bismuth (III) to form a chelate which reduces the fluorescence intensity greatly. And when lambdaex/lambdaem = 305/407 nm, the fluorescence is intensive. There is a linear relationship between the decrease of fluorescence intensity and the concentration of bismuth (III) in the range of 0-0.025 microg x mL(-1). The detection limit is 1.2 x 10(-10) g x mL(-1). A new method of fluorescence spectrophotometric determination of bismuth (III) was developed.