Principles of light pulse generation, mode of action, equipments, application of light pulses, effect of light pulses on foods and microorganisms, advantage and limitation of light pulse treatment.
Answers
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Pulsed-light technology
1. Principles of pulsed light system
Pulsed light is a non-thermal method for food preservation that involves the use of intense, short duration pulses of a broad spectrum to ensure microbial decontamination on the surface of either foods or packaging materials. The inactivation efficiency of pulsed light depends on the intensity (measured in J/cm 2) and number of pulses delivered. Pulsed light is generated using engineering technologies that magnify power many times to convert high speed electronic pulses into short-duration, high peak energy light pulses. The system comprises 3 main components: the power supply, the pulse configuration device, and the lamp. Energy is stored in a high power capacitor for a relatively long period (a fraction of a second) from which it is released to a specially designed xenon lamp unit within a much shorter time (nanoseconds to mlliseconds). High energy delivered to the lamp produces an intense pulse of light focused on the treatment area, which typically lasts a few hundred microseconds. The light produced by the lamp includes broad spectrum wavelengths from UV to near-infrared. The wavelength distribution ranges from 180 to 1100nm: UV (180-380nm), visible light (380-700nm), and infrared (700-1100nm).During the pulse, this system delivers a
spectrum that is 20,000 times more intense than sunlight at the earth’s surface.
The microbiocidal effects of pulsed light increase with light intensity. The frequency of flashing, the number of lamps, and the flashing configuration depend on treatment application.
2. Mechanism of action
The lethal effects of pulsed light can be attributed to its rich broad-spectrum UV content, its short duration, high peak power, and the ability to regulate both the pulse duration and frequency output of flash lamps, which play a major role in microbial destruction