Lecture 7: Thermal Processing Equipment Flashcards
what are preliminary operations?
preparation blanching filling exhausting double seaming processing (cooling, labelling, storage)
what is a retort?
- pressure vessel
- cylindrical shell
- vertical or horizontal
what are essential features in all retorts?
- temp and pressure control
2. temp and pressure uniformity
temp differences in a retort can compromise _____
safety
how does temperature fluctuations compromise product quality?
can result in product overcooking when adjusted for giving the required lethality
what are two major issues of temperature fluctuations on product quality??
temperature variation and stability with respect to:
- Time (eg. system limitations)
- space (eg. loading pattern limitations)
what are pressure controllers used for?
to establish temp and control stability
what are two important factors to consider with pressure controllers and retort temp?
- temp distribution
2. heat (lethality) distribution
temperature establishment in retorts is based on relationships of what?
ie. what is compared in steam tables?
steam temperature and pressure
what happens if air is present in the retort?
what can you do to solve this problem?
- steam pressure will be much lower
- the drop in pressure will cause a drop in temp
can solve this be venting (getting rid of air from the retort)
why is venting important?
to avoid drop in pressure and temperature inside the retort
need to get rid of air to have saturated steam inside
what are vent valves?
a part of a retort which can allow for venting
when do vent valves stay open until? why?
until retort reaches 200F
because incoming steam helps to expel air in the retort, which helps to keep saturated steam in the retort (so that the pressure and temp relationship in the retort is the same as in the steam tables)
venting is very energy _____
intensive
how does the presence of air in the retort affect rate of heat transfer?
air acts as an insulator and interferes with condensation
what are two modes of condensation?
- dropwise (hydrophobic surface)
2. filmwise (hydrophillic)
what are the modes of condensation influenced by?
the presence of air in the retort, since air acts as an insulator. Thus, it is important to get rid of the air
what is the best choice for heating and rapid heat transfer?
steam
retort control can be based on ____ or ___
T or P
compare differences between steam heated water and steam with air overpressure
steam heated water
- good for cans and jars
- water circulation increases heat transfer
steam with air overpressure
- good for all containers
- heat transfer rate is increased by fans inside the retort
what is the function of the bleeder in the retort?
directs the medium in the right direction
what is the function of the vent in a retort?
allows air to come in to protect from a drastic change in pressure
what happens when the pressure in the retort increases too high?
safety valve will open and released pressure
what is the function of the controller in a retort?
controls temp and pressure
describe the steristar steam/air retort
- fan at back wall
- no venting
- conservation of energy
- used for cans and flexible containers
describe the lagarde steam/air retort
- fan at back
- can be operated in water-spray mode and spray cooling
- horizontal 4-car system
describe the water spray retort by lagarde
- 4 car system
- efficient and conserves water usage
- heat exchanger is used for heating and cooling water
describe the FMC overpressure retort barriquand steriflow
- has Weir type water flow
- can be vertical or horizontal
- overhead reservoir for preheating
- short CUT
- good for glass and flexible containers
- water spray
- high flow rate
- small volume of water (efficient recycling and heat exchangers)
- insulated shell
describe a Lagarde ful water immersion retort
- good liquid contact
- more effluent
- preheat chamber conserves heat and reduces CUT
describe the malo crateless retort system
- the crateless retort reduces amount of labour needed since cans can be put straight into the cooker
- conveyer on bottom transports contents across the bottom
- higher capacity and less handling
describe efficiency of rotary retort
containers go through a rotating motion so process time can be reduced (better quality and faster)
describe a hydrostatic sterilizer (FMC)
- saves space
- high capacity operation
- mild agitation which prevents thermal shock for glass
- level of water in legs determines steam temp
describe the FMC continuous turbo cooker
- continuous operation
- pressure cooking and cooling
- high speed operation
- extensively used for soups
describe flame sterilization
- high speed operation
- excellent quality
- high vacuum
- constant headspace
what is cook chex?
cardboard tags with purple heat sensitive ink, which changes color on heating
what compound causes color change in cook chex?
chromium compound changes color on heating
can be formulated to be sensitive to different times and temperature combinations
with cook chex, what color is it when dry and cool?
what color is it when wet and heated?
pink: dry and cool
green: wet and heated
what does a pink retort check mean?
unexposed to heat
what color is a pass retort check?
green
what color is a failed retort check?
grey
