food preservation by irradiation

what are the two forms of irradiation used

ionizing radiation
non-ionizing radiation

what does the strength of radiation depend on?

on the wavelength, the shorter the wavelength the more energy the radiation has

why do we use irradiation to preserve foods?

- extends shelf life
- kill spoilage m.o and spores
- enhances safety
- delays ripening in fruits like bananas, by destroying DNA (mutation)
- prevents sprouting in potatoes, garlics and onions
- kills insects in rice and pasta

what is ionizing radiation

radiation that has enough energy to remove electrons from atoms, forming ions

what are the 3 types of ionizing radiation?

1) beta rays

2) gamma rays

3) X-rays

what is the ionizing sources that have been approved internationally for food processing?

gamma rays produced from radioisotopes

what are the irradiation sources for ionizing radiation?

- Cobalt60 and Cesium137
- machine generated electron beam
- x-rays

what are the 2 mechanisms of ionizing radiation?

direct and indirect

direct effect of ionizing radiation

damaged nucleic acids in the DNA when the high energy electron hits the DNA

indirect effect of ionizing radiation

generates free radials when high energy electrons hit water molecules

3H20 -\> OH- + H+ + H2O2 + H2

what is the unit of irradiation?

Gray, Gy

how does type of bacteria determine resistance to ionizing radiation

gram + more resistant than gram -
spore forming more resistant than non-spore forming

how does temperature at which food is stored determine the resistance to ionizing radiation?

frozen foods are more resistant since there is less water to be ionized

what is the name of the method of sterilizing food by irradiation?

radappertization
30-40 kGy

what irradiation is equivalent to pasteurization of milk?

radication
2.5 - 10 kGy

describe UV light

powerful bactericidal agent

most effective wavelength for UV light

2,600 A

how does non-ionizing radiation cause cell death?

absorbed by proteins and nucleic acids causing photochemical changes in the cell that lead to cell death

lethal mutations

UV penetration

- poor penetration capacity
- limit its food use to surface applications like juices