Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform
Thesis (PhD.)
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| Format: | Thesis |
| Language: | English |
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Universiti Teknologi Malaysia
2024
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| Online Access: | http://openscience.utm.my/handle/123456789/932 |
| _version_ | 1796848934498336768 |
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| author | Arshad, Rai Naveed |
| author_facet | Arshad, Rai Naveed |
| author_sort | Arshad, Rai Naveed |
| collection | OpenScience |
| description | Thesis (PhD.) |
| first_indexed | 2024-03-05T17:35:06Z |
| format | Thesis |
| id | oai:openscience.utm.my:123456789/932 |
| institution | Universiti Teknologi Malaysia - OpenScience |
| language | English |
| last_indexed | 2024-03-05T17:35:06Z |
| publishDate | 2024 |
| publisher | Universiti Teknologi Malaysia |
| record_format | dspace |
| spelling | oai:openscience.utm.my:123456789/9322024-01-14T12:00:42Z Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform Arshad, Rai Naveed Food—Pasteurization Pulse generators Electric fields Electroporation Thesis (PhD.) Pulsed electrical fields (PEF) has been considered as an efficient method for the sustainable processing of liquid food at reduced temperatures. PEF pasteurization preserves the liquid food's freshness and nutrients compared to the traditional thermal pasteurization. However, PEF suffers a heterogeneous or non- uniform distribution of electric field. It raises the dissipation of electrical energy in the liquid, and ultimately the temperature of the treated food sample increases. The electric field intensity, liquid flow behaviour, and liquid residence time are the leading causes of this heterogeneous treatment. The electric field uniformity in a continuous treatment chamber is correlated to the liquid laminar velocity profile and heat distribution. It is desired to improve the electric field uniformity, prevent any dielectric breakdown, and prevent the occurrence of hotspots. Apart from electric field stress due to its non-uniformity, hotspots can also be due to the applied shape of pulses. High-voltage short duration rectangular or exponential decay (ED) pulses are known to cause significant lethality to biological cells. The ED pulse is usually characterized by a narrow peak and a lengthy tail. However, the short front of ED makes it less efficient for PEF based pasteurization. This research proposes a solution to the field uniformity problem with an improved treatment chamber using insulator sieves and a solution to the pulse waveform problem using a double exponential (DE) waveform. The improved coaxial treatment chamber with sieves was simulated in COMSOL Multiphysics. The effectiveness of the DE waveform was validated using Matlab. Based on the simulation model, the proposed coaxial treatment chamber with sieves and static mixer resulted in an improved liquid flow homogeneity and hence reduced local temperature peaks. A three-stage insulated-gate-bipolar-transistors (IGBT) based Marx generator giving the DE waveform was designed and constructed. Each stage was composed of a parallel combination of two IGBTs, two gate-drivers, an optocoupler, and an isolated DC-DC converter. The performance of the improved treatment chamber together with the DE shaped PEF, known as the electroporator, was studied using chemical and microbial tests. The condition of PEF treated and untreated orange juice samples were determined after 9 days’ storage at 4 °C. Treated orange juice using the low-temperature, long-time thermal pasteurization was also used for comparison. A lowest microbial growth was observed in both the PEF treated with sieves and thermally treated food samples than that untreated sample. However, the treated juice visual and chemical colour analysis showed that the PEF-treated sample was brighter compared to the thermally processed sample. Furthermore, smaller changes in °Brix and pH values were observed in the PEF treated samples than those for the thermally treated ones. Also, the reduction in vitamin C content in the PEF treated samples was smaller than that in the thermally treated samples. For the samples studied, it can be concluded that the PEF process using the proposed electroporator has successfully preserved the microbiological stability, colour and vitamin C content of the food samples. Its performance was better than that using the thermal procedure. This study provides significant findings in developing and utilizing PEF based food treatment to inactivate microorganisms. It hence may be further developed for industrial applications. Faculty of Engineering - School of Electrical Engineering 2024-01-14T03:22:34Z 2024-01-14T03:22:34Z 2021 Thesis Dataset http://openscience.utm.my/handle/123456789/932 en application/pdf application/pdf Universiti Teknologi Malaysia |
| spellingShingle | Food—Pasteurization Pulse generators Electric fields Electroporation Arshad, Rai Naveed Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title | Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title_full | Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title_fullStr | Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title_full_unstemmed | Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title_short | Improved electroporator for liquid food pasteurization through continuous flow and double-exponential impulse waveform |
| title_sort | improved electroporator for liquid food pasteurization through continuous flow and double exponential impulse waveform |
| topic | Food—Pasteurization Pulse generators Electric fields Electroporation |
| url | http://openscience.utm.my/handle/123456789/932 |
| work_keys_str_mv | AT arshadrainaveed improvedelectroporatorforliquidfoodpasteurizationthroughcontinuousflowanddoubleexponentialimpulsewaveform |