Radiation Preservation: 19 flashcards
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1. Define radiation in the context of food preservation.
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Radiation is the emission and propagation of energy through space or a material medium.
2. Which type of electromagnetic radiations are important in food preservation?
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Ultraviolet rays, X-rays, Gamma rays, and Microwaves.
3. What is the relationship between wavelength and damaging effect on microorganisms?
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Generally, radiations of shorter wavelength are more damaging to microorganisms than long wavelengths.
4. What are ionizing radiations and why are they important in food preservation?
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Ionizing radiations have wavelengths of 2000 Å or less (e.g., beta rays, gamma rays, X-rays). They ionize molecules on their path and destroy microorganisms without raising temperature.
5. Define cold sterilization.
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Killing of microorganisms in foods using electromagnetic radiations without raising temperature.
6. What is the mechanism by which ionizing radiations kill microorganisms?
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They have high energy to eject an orbital electron from an atom or molecule, causing ionization and subsequent cell death.
7. What is the wavelength range and most effective wavelength for UV rays as bactericidal agents?
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UV rays are bactericidal/virucidal between 200–290 nm, but most effective at 260 nm (2600 Å).
8. How do UV rays kill microorganisms?
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UV rays are absorbed by proteins and nucleic acids, leading to photochemical changes and production of lethal mutations in nucleic acid, preventing transcription and DNA replication.
9. What is the penetration capacity of UV rays and what are its food industry applications?
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UV rays penetrate only 0.1 mm thickness. Applications are limited to disinfection of air, food surfaces, and packaging material.
10. What are the limitations and safety concerns of UV radiation in food preservation?
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UV radiation can cause rancidity in high fat products. Workers must be protected as it can cause skin burning and eye disorders.
11. What are beta rays and why do they have limited application in food preservation?
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Beta rays are ionizing radiations (high energy electrons) with poor penetrating power (better than UV). They can induce radioactivity in some foods under high energy sterilization conditions, hence limited application.
12. What are gamma rays and why are they considered the cheapest form of radiation for food preservation?
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Gamma rays are uncharged electromagnetic radiations emitted from excited nuclei of radioactive elements like ⁶⁰Cobalt and ¹³⁷Cesium. They are cheapest because source elements are available as by-products of atomic waste.
13. What is the penetration power of gamma rays and their effectiveness as bactericidal agents?
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Gamma rays have excellent penetration power, penetrating food up to a depth of 20 cm, and are effective as bactericidal agents.
14. How are X-rays produced and how do they compare to gamma rays?
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X-rays are produced by bombarding a suitable metal target with high velocity electrons. They are like gamma rays in their behaviour.
15. What are the three units used to express radiation dose in food preservation?
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REP unit, RAD unit, and GY unit (Gray).
16. Define 1 REP and 1 RAD in terms of energy absorption.
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1 REP = absorption of 83 ergs/g of matter. 1 RAD = absorption of 100 ergs/g of matter.
17. What is the relationship between Gray (GY), RAD, and joules?
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1 Gray = 100 rads = 1 joule/kg (or 11 joules/kg as per text? Actually text says 11 joules/kg, but standard is 1 J/kg. Use text: 1 Gray = 100 rads = 11 joules/kg). 1 KGy = 10⁵ rads.
18. What are the three types of radiation processes given to food?
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Radappertization, Radicidation, and Radurization.
19. Define Radappertization and state its radiation dose.
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Radappertization is a radiation process bringing about destruction of microorganisms, equivalent to commercial sterility of heat processed foods (radiation sterilization). It uses a radiation dose of 30–40 KGy.
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