Microwave-Based Technique For Glucose Detection

Glucose biosensor is generally based on reaction between glucose and enzyme glucose oxidase (GOD) that produces gluconic acid and hydrogen peroxide. The gluconic acid is a conducting medium while hydrogen peroxide is a polar molecule. This work discovers the changes of dielectric properties due to conductive loss below 4 GHz and dipole orientation of above 4 GHz of this reaction. The difference between the dielectric properties of an enzyme and glucose-enzyme reaction can be related to the glucose concentration in the sample. The dielectric properties of glucose solutions, enzyme GOD and glucose-enzyme reaction were measured using the Open Ended Coaxial Probe with frequency range from 200 MHz to 20 GHz at room temperature (25 'C). Two types of juice are used in this study; blackcurrant juice and lychee juice. The actual glucose content in juice samples were analyzed using High Performance Liquid Chromatography method. This technique has also been applied using the microstrip sensor for measuring glucose concentration in glucose solution, blackcurrant juice and lychee juice. The result shows that the highest sensitivity for the differences in dielectric changes with glucose concentrations due to the effect of ionic conductivity and dipole orientation were found at 0.99 GHz and 16.44 GHz respectively. The changes in dielectric loss are preferable for derivation of glucose concentration. In this proposed technique, the detection limit of glucose concentration is as low as 0.01 M (0.20 g/100 ml) with optimum ratio of 1:3 for an enzyme and glucose. Lychee juice has a higher dielectric loss difference for both frequencies followed by blackcurrant juice and glucose solution due to the contribution of free ions in the juice. The sensitivity of attenuation measurement using microstrip sensor is dependent on the dielectric loss of materials. The sensitivity of measurement about 0.002 dB/ (mg/ml) at 0.99 GHz and 0.004 dB/ (mg/ml) at 16.44 GHz which are comparable to the current microwave techniques. This technique gives benefit to the future development of microwave biosensor by which both ionic conductivity and dipole effects are occurred simultaneously

Microwave‐based biosensor for glucose detection

In this project, microwave‐based biosensor for glucose detection has been studied. The study is based on the dielectric properties changes at microwave frequency for glucose‐enzyme reaction. Glucose interaction with glucose oxidase (GOD) produced gluconic acid and hydrogen peroxide. The reaction of the glucose solutions with an enzyme was carried out in 1:3 of glucose and enzyme respectively. The measurements were done using the Open Ended Coaxial Probe (OECP) coupled with computer controlled software automated network analyzer (ANA) with frequency range from 200MHz to 20GHz at room temperature (25 °C). The differences of enzyme and glucose‐enzyme reaction were calculated and plotted. In the microwave interaction with the glucose‐enzyme reaction, ionic conduction and dipole molecules was detected at 0.99GHz and 16.44GHz respectively based on changes of dielectric loss factor

Surface modification via alginate-based edible coating for enhanced osmotic dehydration mass transfer of ginger slices

Ginger has a high moisture content, which makes it highly susceptible to spoilage. Therefore, the shelf life can be extended through drying. In the drying process, osmotic dehydration is applied as pre-treatment due to its simple operation and energy-saving process for removing moisture from food. However, large solute gain during the osmotic dehydration has become the major challenge of this process as it has a negative impact on the final product. The edible coating is the key step to circumventing this issue. Alginate is a potential candidate for the coating material to enhance the mass transfer kinetics of the osmotic dehydration process. This study investigated the surface modification of ginger slices caused by the cross-linker calcium chloride and plasticizer glycerol on alginate coating using a Scanning Electron Microscope. Furthermore, the kinetics of water loss and solute gain were evaluated and modelling aspects were conducted. It was observed that the surface roughness of ginger coated with a combination of alginate, glycerol and calcium ions has reduced. This facilitated the mass transfer process, which was observed to have a high water loss and a lower solute gain. The Peleg model presented the best fitting model of mass transfer kinetics during osmotic dehydration of ginger slices. From this work, it can be deduced that alginate-based coating can be a promising pre-treatment step in the osmotic dehydration process

Effects of operating factors on osmotic dehydration of broccoli stalk slices

In this study, effects of sucrose concentration (40–60% w/v), immersion time (1–5 h), and temperature (25–65°C) on water loss (WL) and solute gain (SG) during osmotic dehydration of broccoli stalk slices were quantitatively investigated using response surface methodology. It was found that concentration of sucrose solution, immersion time, and temperature affected the WL during osmotic dehydration process. Significant factors affecting the SG are the temperature and immersion time. The operating conditions to obtain water removal of 62% with solute intake of 7% were found to be at a sucrose concentration of 56% w/v, temperature of 42°C, and immersion time of 4 h

Variation of microwave dielectric properties in the glucose biosensor system

Glucose biosensor is generally based on the reaction between glucose and glucose oxidase, which produces gluconic acid and hydrogen peroxide. The gluconic acid is a conductive material, while hydrogen peroxide has polar molecules. This article examines the changes of dielectric properties due to the conductive loss below 2 GHz and dipole orientation of above that frequency of this reaction. The difference between the dielectric loss of glucose solution and the dielectric loss of glucose-enzyme reaction can be related to the glucose concentration in the samples, such as orange juice, black grape juice, sugarcane juice, and sapodilla juice. A good sensitivity to these differences due to the effect of ionic conductivity and dipole orientation was found at 1 and 16.44 GHz, respectively. The minimum detection limit of glucose concentration in the proposed technique was about 0.01 M (0.20 g/100 ml) with an optimum reaction ratio of about 1:1 between the enzyme solution and the glucose solution. This technique could benefit the future development of microwave biosensor by which both ionic conductivity and dipole effects can be considered simultaneously

Superoleophilic-hydrophobic Kapok oil sorbents via energy efficient carbonization

High oil sorption, dynamic oil/water selectivity and oil retention are essential for advanced materials to remediate offshore oil spills. In this context, superoleophilic-hydrophobic kapok bundles, synthesized via a simple, one-step and energy efficient carbonization (300°C), were investigated as effective oil sorbents. It was shown that the surface roughness and intrinsic graphite phase of the kapok bundles were tunable by varying the carbonization temperature, thereby enhancing their oil sorption and retention. Lumen preservation enables the carbonaceous kapok bundles to exhibit tunable oil sorption capacities of 34.0 g/g – 95.5 g/g for various types of oil, unrivaled among other oil spill recovery methods. The origin of oil permeability into lumen is attributed to nanopores observed for the first time on the carbonaceous kapok fibers. The kapok bundles selectively absorbed oil slick under vigorous water vortex and demonstrated distinctly high oil retention of 100% under gravitation force. Multiple oil sorption-desorption and compression cycles (up to 15 times) demonstrate a considerable promise of the carbonaceous kapok bundles for high reusability with low environmental impact