b. to study the potential and effects of microwave treatment during various stages of turmeric processing techniques.

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1 CHAPTER VII: CONCLUSION AND SCOPE FOR FUTURE Formatted: Font: 14 pt WORK 7.1 ASPECTS OF THIS RESEARCH WORK Formatted: Space Before: 6 pt The principle objectives of this research work were: a. to clarify the means and procedures involved in the design of a high-tech multi-mode control system for controlling the microwave power of a microwave drying applicator, and b. to study the potential and effects of microwave treatment during various stages of turmeric processing techniques Design of an appropriate microwave drying applicator Power control in the microwave source was realized by integral cycle control, phase control, PWM control and linear control power regulators. The electrical power of the microwave oven could be controlled by any one of the above four control modes. The system performance of multimode controlled system was analyzed and evaluated with combined microwave and hot-air convective drying system used for samples of turmeric fingers. The study leads to the following conclusions: 1. The proposed triac power control with microcontroller 89C51 could be successfully used for multimode control system for power regulation with maximum efficiency. 2. In a designed and modified multi-controlled microwave-hot-air convective drying unit, the input electrical power to the magnetron could be controlled with any control mode. All the strategies applied for controlling microwave power output of magnetron are found achievable. 3. The system performance reveals that the average microwave power absorbed by the load is the maximum in the case of the integral cycle control mode and the minimum in the case of the linear control mode. 4. The average load efficiency is the maximum in the case of integral cycle control mode and the minimum in the case of linear control mode. 137

2 5. The average values of the microwave power absorbed by the load and average load efficiency for the phase control mode are at moderately good levels. 6. The integral cycle control mode had several drawbacks. Hence, the phase control mode is found to be the most suitable control mode for a microwave drying applicator used for processing of turmeric fingers.. 7. The product color and sensory attributes were found to be dependent on very small scale, with microwave power control methods. The high temperature of the sample had a negative effect on the color while the high air velocity increased the textural consistency. 8. The effects of the different power control methods on the drying kinetics and product qualities were different. In all the four control modes used for controlling the microwave power of the drying applicator, the drying time increased with the decrease of microwave power density and increase in the air velocity. 9. During drying process of turmeric fingers with combined microwave-hot-air convective drying, the drying rates of the integral cycle control mode are significantly higher than those of other control modes. 10. The accurate temperature control could be realized using phase control, PWM control, and linear control methods, when compared with integral cycle control method. 11. It is also reasonable to expect higher power efficiency using phase control and integral cycle control rather than when using PWM control and linear control, because the latter processes always consume power at the full capacity. 12. The benefits of different air velocities were clarified because the product temperature rose no further during falling drying rate periods. But the disadvantage is that the more electrical energy is consumed Effects of microwave drying on various stages of turmeric processing The potential and effects of microwave treatment on various stages of the turmeric processing techniques have also been studied, covering the effects of microwave treatment on soil, turmeric seed rhizomes, stability of turmeric constituents, control of insect pests in stored turmeric fingers and in turmeric powder. The studies lead to the following conclusions: 138

3 1. Microwave treatment of the soil used for turmeric rhizomes seeds appears to be a relatively easy, rapid and inexpensive method of pasteurizing relatively small amount of soil. 2. If more microwave power is used for radiation treatment of the soil to control of soil microorganisms, better results are obtained. 3. Better results are obtained for longer durations of treatment times. 4. Better results in reduction of population of soil microorganisms are obtained with low levels of moisture content in the soil. 5. The mineral type of soils gave better results regarding the reduction in population of soil microorganisms with microwave treatment. 6. Microwave treated water and soil used for turmeric rhizome plants gave better results, where as, microwave treated turmeric seed rhizomes gave adverse results as far as the turmeric plant growth is concerned. 7. Stabilization of constituents of stored turmeric rhizome fingers treated with microwaves is better than the stabilization of the values of the constituents when turmeric products are treated with a conventional drying process. 8. Stabilization of constituents of stored turmeric sliced fingers treated with microwaves is the best of all. 9. Microwave treatment is most effective method and gave most positive results for stored turmeric fingers. 10. Microbial load has been observed at tremendously decreased level with microwave treatment during storage period. 11. Microwave treatment using drying / irradiation is the best alternative to chemical and fumigation treatment methods. 12. With microwave treatment, the quality of the output product is found better, with its non-contaminated non-toxic and hygienic nature. 7.2 CONTRIBUTION AND CONCLUSION OF RESEARCH WORK The work presented here has made an original contribution to the body of knowledge surrounding the development of applications with microwave drying applicator in the processing techniques applied to turmeric rhizome fingers. 139

4 1. The design considerations of four control modes for regulating the microwave power of the magnetron used in microwave drying applicator have been identified and summarized to enable the researcher for future potential developments and for the benefit of future potential applications development. 2. The potential of microwave drying / irradiation for control of soil microorganisms was investigated. The results presented show a better decrease in population of soil microorganisms. 3. The potential and effects of microwave irradiation on various types of soils, levels of moisture contents in the soil, using different durations of treatment time and the amount of microwave power used for treatment of the soil were investigated. The results presented show a better a decrease in the population of soil microorganisms. 4. Microwave treatment administered to the water and soil used for the planting of turmeric rhizome seeds was investigated. The results presented show better output performance with regards to turmeric seed rhizome plant growth. 5. Microwave irradiation of stored turmeric fingers, stored turmeric sliced fingers and stored turmeric powder was investigated. The results presented show a better stabilization with regards to the composition of constituents. 6. The potential of microwave treatment on turmeric fingers and turmeric powder during storage period was investigated. The results presented show a better decrease in microbial load reducing the adverse effects giving better quality and without loss in quantity of output product. 7.3 SCOPE OF FUTURE WORK Formatted: Space Before: 6 pt, Numbered + Level: 1 + Numbering Style: 1, 2, 3, + Start at: 1 + Alignment: Left + Aligned at: 0.5" + Tab after: 0.75" + Indent at: 0.75" Formatted: Space Before: 6 pt Further studies could be conducted along the following lines of thought: 1. Power control using a three-phase AC power supply: The current study was concentrated on control using a single-phase AC power supply to the microwave drying applicator. In many industrial applications the electrical power supply to microwave processing equipment is of the three-phase type. There may be a need to develop a three-phase AC input power regulator to control the microwave power. 140

5 2. Microwave electromagnetic waveform control: The current study applied an indirect strategy to control the microwave power by varying the input electrical power with the help of four control modes. The microwave power could be directly controlled by regulating the microwave electromagnetic wave?-form. 3. The magnetic field control inside the magnetron: Microwave power could be changed by adjusting the magnetic field strength inside the magnetron. In such cases an electromagnet should be introduced instead of a permanent magnet. 4. Introduction of multiple magnetrons and cavities: Because of non-uniform distribution of microwave field in a single magnetron cavity, the development of an apparatus which can accommodate multiple magnetrons and cavities is needed. 5. The present work is based on laboratory test results. It is necessary to conduct field experiments to prove the utility of microwave radiation for the purposes of turmeric processing. 6. The present work is based on batch process at laboratory level. It is necessary to develop a continuous type of process for treatment of turmeric rhizome fingers on a large scale. 7. Essential basic research must be carried out to develop microwave applicators for the thermal processing of turmeric rhizome fingers, in order to ensure market growth, competitiveness in the international market, and the availability of fresh, safe and high quality produce. 8. The future promises abundant electric power from renewable sources. This will favor the use of electro-technologies, along with a microwave drying applicator, in the processing of turmeric rhizome fingers. 141