Puffing Flashcards
what happens to the bulk density of a product that has been puffed
reduced
how is bulk density reduced
moisture is removed and structure becomes more porous
whhy puff?
prevents shrinking that occur with traditional dehydration which makes rehydration difficult
puffing keeps the product expanded and makes structure more porous so rehydration is easier
classifications of puffing processes
phase change puffing
puffing induced by chemical reaction
absorption puffing
adsorption puffing
describe phase change puffing
the water in the material is ‘superheated vapour’ = temp higher than 120C
water flash vapourises into a gas which takes up more space creating pressure inside the food
explain puffing induced by chemcial reactions
reactions in which the product is gas
CO2 during fermentation
baking soda
describe absorption puffing
caused by the reduction of pressure in a saturated system
-soda: has carbonic acid under pressure, release turns it into CO2
describe adsorption puffing
gas is adsorbed on the external or internal surface of a product
-used in tobacco processing
the organisation of the structure relies on (20
increasing the plasticity of the food surface
rapid phase change of moisture inside the food (flash vapourisation)
how can plasticity be improved
blanching followed by light pre-drying
what happens to the starch in food products as it undergoes the puffing processes
becomes gelatinised and makes the product more plasticised
-no longer looks like deposits
what is ocmmercially used as solid particles on fluidised bed
salt, traditionally sand
types of rheological models
spring, linear elasticity: applying force to the string expands, spring will return to normal upon removal of straining
dashpot/linear viscous model : applying force will permentantly change, materia has no strain memory
describe the rheological nature of fresh potato
really strong springs that require a lot of force to change
describe the rheological nature of blanched/intermediate temp of potato
modified to material be able to respond to any pressure/ improved plasticity
describe rheological nature of puffing temp potato
pressure created by flash vapourisation creates pressure on plastiicised material and it expands which creates dashpots
-potato cube is dehydrated which fixes the expansion
how many stages to puffing expansion are ther
3
1: strong spring
2: weaker springs, yeilds to force, strong dash pot
3: dashpot
how to reverse dashpot formation
applying force in the equal and opposite direction
-crushing the product is an example
factors that effect expansion
pre-drying time: there is an optimal time
puffing time/ how long material is kept at puffing temp: increases with time
puffing temp: increases with the temp
sample size: optimal size
all different for different products
describe physical conditions required for the production of puffed potato
increase plasticity through blanching
rapid phase change of water to vapour through flash vapourisation
describe the thermal conditions required for puffing
blanching >70 but <90
flash vapourisation >120
