4.3 food processing: preservation by dehydration and irradiation

how does water activity impact dehydration?

lower water activity slows microbial growth, extends shelf life and improves food stability

what is tunnel drying?

food dried on trays moving through a heated tunnel - used for vegetables and crops

what is roller drying?

food dried by contact with heated drums - used for milk powder and eggs

what is sun drying?

uses direct sunlight to dry food - low cost but hygiene risks

what is warm air drying?

air blown upward to keep food separated and dry - used for small fruits and vegetables

what is spray drying?

food atomised into droplets and sprayed into hot air - used for milk, eggs, tea and spices

what is freeze drying?

removes moisture at low temperature and pressure - preserves nutrients and texture, used for coffee and vitamins

what is food irradiation?

application of ionizing radiation to kill microbes, insects and delay spoilage in food

what types of radiation are used in food irradiation?

gamma rays, x-rays and electron beams

how does irradiation reduce microbial spoilage?

kills bacteria and pathogens without heat or chemicals

how does irradiation prevent insect damage?

destroys insects and larvae in grains, spices and dried foods

how does irradiation inhibit sprouting and ripening?

slows down biological processes in fruits and vegetables - extends shelf life

how do consumers react to irradiated foods?

some concern over safety and wholesomeness, but acceptance is growing

how does dehydration affect organoleptic properties?

reduces moisture, concentrates flavour, changes texture and appearance

how does irradiation affect organoleptic properties?

minimal changes to taste, texture and appearance