Pansa Liplap

Effect of Dielectric Properties of a Solvent-Water Mixture Used in Microwave-Assisted Extraction of Antioxidants from Potato Peels

The dielectric properties of a methanol-water mixture were measured at different temperatures from 20 to 80 °C at two frequencies 915 MHz and 2450 MHz. These frequencies are most commonly used on industrial and domestic scales respectively. In this study, the dielectric properties of a methanol-water mixture were found to be dependent on temperature, solvent concentration, and presence of plant matrix. Linear and quadratic equations were developed to establish the dependency between factors. At 2450 MHz, the dielectric constant of methanol-water mixtures was significantly affected by concentration of methanol rather than by temperature, whereas the dielectric loss factor was significantly affected by temperature rather than by methanol concentration. Introduction of potato peel led to an increase in the effect of temperature on the dielectric properties of the methanol fractions. At 915 MHz, both the dielectric properties were significantly affected by the increase in temperature and solvent concentration, while the presence of potato peel had no significant effect on the dielectric properties. Statistical analysis of the dissipation factor at 915 and 2450 MHz revealed that both temperature and solvent concentration had a significant effect on it, whereas introduction of potato peels at 915 MHz reduced the effect of temperature as compared to 2450 MHz. The total phenolic yield of the microwave-assisted extraction process was significantly affected by the solvent concentration, the dissipation factor of the methanol-water mixture and the extraction time.

Effect of microwave and hot air drying on flax straw at controlled temperatures

Flax stems were subjected to microwave drying at controlled temperatures. The rate of drying was then compared with conventional hot air drying. The product temperature was maintained at 40°C, 60°C and 80°C for both microwave and hot air drying. The moisture content of flax stem was about 70% (wet basis). The microwave drying was conducted in a microwave apparatus which recorded mass, product temperature, incident microwave power, reflected microwave power and inlet/outlet air temperature. The final moisture content for experiment was set to 9% (wet basis). Microwave-convective drying ensured about 30% to 70% reduction of drying time for drying flax straw as compared to hot air drying. Curve fitting with different mathematical models were carried out and all the models were fitted well for both hot air and microwave drying. The tensile strength of flax straw, measured with an Instron apparatus, increased with an increase in the processing temperature of both processes. Hot air dried flax straw showed the greatest tensile strength and modulus of elasticity at processing temperatures of 60°C and 80°C with a significant difference.

Method for Determining the Respiration Rate of Horticultural Produce Under Hyperbaric Treatment

A method was developed to determine the metabolic respiration rate (RRm) of fresh produce during the transient period at the beginning of a hyperbaric treatment. This method allowed for the correction in the apparent respiration rate (RRap) by considering the dilution effect of flushing the system and the error associated with gas solubilisation as the gas partial pressure varied. The dilution process was simulated by using the general equation for exhaust ventilation, thus allowing for the elimination of the dilution effect during the calculation of the net respiration rate (RRN). The error associated with the CO2 solubilisation in the flesh of the produce was solved by measuring the CO2 solubility in the tissues of tomato at various CO2 partial pressures and using this value to generate a mass balance of CO2 within the system. The RRm was estimated by incorporating the initial respiration rate (RRi) of untreated fruits with the respiration rate at equilibrium (RRe). The kinetic of the RRm was proposed to follow a negative exponential equation. The constant value (k) of the RRm model was found to decrease exponentially with the partial pressure of CO2 at equilibrium which affected the amount of gas solubilised and the time to reach equilibrium. The developed method should be validated for the RRm of other produce during the transient period at the beginning of a hyperbaric treatment.

The Potential of High Moisture Biomass for Energy Production Using Plasma – Assisted Gasification

Gasification of biomass has been widely used for energy production. However, biomass feedstock must be low in moisture (< 20 % w.b.), inevitably requiring drying process which is both energy and time consuming. This paper shows the potential of high-moisture biomass gasifying using plasma arc as an external heat supply. It was found that high-moisture biomass can be used as feedstock in the plasma-assisted gasification process. The plasma arc maintained gasifier temperature high enough for reactions involved. The efficiency of the plasma-assisted gasification system operated with high-moisture biomass was more or less the same with that of conventional gasification operated with low-moisture biomass. When the drying energy was taken into account, the efficiency of the plasma gasification system is 15% higher than that of conventional gasification system. Overall, the plasma-assisted gasification system can be operated with high-moisture biomass efficiently and reduces the processes and energy for biomass preparation.

Effect of Steam on the Energy and Activated Carbon Production of A Pilot-Scale Downdraft Steam Co-Gasification

A by-product from gasification technology is charcoal that can be developed as high-quality activated carbon by activation technology such as steam, chemical, high nitrogen and other activation methods. Thus, in this study, the concept of combined energy and activated carbon production from coconut shell was investigated using a pilot-scale open top downdraft steam co-gasification with steam injected into the reduction zone of the gasififier. A pilot-scale experiment on coconut shell steam co-gasification aimed at generating electricity; therefore, the reactor temperature profile, syngas characteristics, performance of the syngas in the production of electricity were included in the steam co-gasification and iodine absorption of the charcoal. The result showed that the study of combined energy and activated carbon production from coconut shell is a way of using resources efficiently, increasing quality of the by-product, and using clean technology.

Effect of hyperbaric treatment on respiration rates and quality attributes of sweet corn

Effects of three-day hyperbaric and low temperature treatment on the respiration rates and quality attributes of sweet corn were studied. Quality attributes were also monitored over four days of storage at ambient conditions. Best results were obtained from cold storage at 0°C, but hyperbaric treatment showed positive effects on quality retention of sweet corn. An inverse relationship was observed between the pressure levels applied and respiration rates. The higher the pressure applied, the lower the respiration rates. Fresh weight, TSS and kernel colour were better retained as the applied pressure level increased. However, husk colour became paler with an increase in pressure level. After storage, the measured quality attributes were not evidently affected by pressure treatments. Even though hyperbaric treatment was not as effective as the cold temperature storage condition in extending sweet corn shelf life, promising results were observed for a short-term storage without refrigeration.