4.2 food processing: preservation by temperature control

what is pasteurisation?

heat treatment to kill most bacteria - e.g. milk heated to 72°C for 15 seconds (HTST)

what is sterilisation?

thermal process that kills all bacteria - used in canned foods and aseptic packaging

what is canning?

sealing food in metal containers and heating to destroy bacteria - extends shelf life

what is aseptic canning?

food and packaging sterilised separately before sealing - used for milk and juices

what is chilling?

cooling food to 1-5℃ to slow bacterial growth - used for perishable items

what is horizontal plate freezing?

freezing pre-packed food between cold plates - used for fish fillets and meat

what is blast freezing?

cold air blown over food to freeze quickly - used in commercial kitchens

what is fluidised bed freezing?

cold air sprayed upward through mesh belt - rapidly freezes small items like fruit and veg

what is cryogenic freezing?

uses liquid nitrogen or dry ice at extreme cold - creates small ice crystals, preserves texture

what are advantages of heat processing for manufacturers?

longer shelf life, safer products, easier transport and storage

what are disadvantages of heat processing for manufacturers?

equipment cost, energy use, possible nutrient loss

what are advantages of heat processing for consumers?

safe food, longer storage, convenience

what are disadvantages of heat processing for consumers?

changes in taste, texture, and nutrient content

what are advantages of cold processing for manufacturers?

preserves nutrients, maintains quality, suitable for delicate foods

what are disadvantages of cold processing for manufacturers?

high energy costs, need for specialised equipment

what are advantages of cold processing for consumers?

better taste and texture, less nutrient loss, safer storage

what are disadvantages of cold processing for consumers?

freezer burn, low temperature damage, limited shelf life

how does heat processing affect organoleptic properties?

can soften texture, dull colour, alter flavour - e.g. tinned fruit is softer than fresh

how does cold processing affect organoleptic properties?

can preserve texture and flavour, but may cause freezer burn or dryness