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)