Lecture 8: Quality Optimization in Thermal Processing

Question 1

what is the aim of techniques in quality enhancements?

Answer 1

improving heat transfer to the product

Question 2

what is heat transfer in canned foods driven by?

Answer 2

1. convective heat transfer: the rate of heat transfer from the heating medium to the can
2. heat transfer within: can be mixed convection and conduction rate heat transfer

Question 3

what factors are involved with a shorter rate of heat transfer?

Answer 3

• shorter process time/quicker turnover
• more uniform temp
• less overcooking of product
• bettwe quality retention

Question 4

what is the heat transfer equation?

Answer 4

q= h * A * deltaT = k * A * deltaT * x

Question 5

the graph of relative D value vs. temperature provides what data?

Answer 5

relative resistance of bacteria to thermal destruction

Question 6

in the relative D vs temp graph, what has the highest D value? why?

Answer 6

nutrients b/c they are more stable than microorganisms

Question 7

do nutrients or microorganisms have a higher z value?

Answer 7

nutrients have a higher Z value

Question 8

are nutrients or microorganisms less sensitive to changes in temperature? how can this be seen?

Answer 8

nutrients are less sensitive, which can be seen by their flatter slope in the relative D vs temp graph

Question 9

in the relative D vs temp graph, what does a steeper slope indicate?

Answer 9

more sensitive to change in temp

Question 10

vegetative bacteria has a very ___ slope

Answer 10

steep

Question 11

what does HTST stand for?

Answer 11

high temperature short time

Question 12

what does UHT stand for?

Answer 12

ultra high temperature

Question 13

everything on the left of the thermal destruction curve is _____

everything on the right of the curve is ____

Answer 13

underprocessed

overprocessed

(process times should be right on the curve)

Question 14

what are some different types of heat exchangers?

Answer 14

• plate and frame
• tubular
• swpet (Scrapped) surface

Question 15

what are some process benefits from HTST and UHT?

Answer 15

• hats rapidly for liquids
• involves packaging in thin profile forms
• for cans that undergo agitation during processing (either liquids or semi-solids)
• for aseptic processing and packaging

Question 16

what is HTST not suitable for?

Answer 16

conduction heating type of products in large containers

Question 17

what does HTST do in thin profile processing?

Answer 17

• increases surface area

- reduces thickness

Question 18

what is thin profile processing use for?

Answer 18

conduction heating foods

Question 19

what are the three layers in a retort pouch used in thin profile processing?

what is the role of each layer?

Answer 19

1. outer layer: strength and printability
2. middle layer: barrier properties
3. inner layer: heat sealability and food contact

Question 20

in the retort pouch used in thin profile processing, which layer is used for heat sealability?

Answer 20

inner layer

Question 21

in the retort pouch used in thin profile processing, which layer is used for strength and printability?

Answer 21

outer

Question 22

in the retort pouch used in thin profile processing, which layer is used for barrier properties?

Answer 22

middle

Question 23

what is over pressure processing used to process?

Answer 23

• retort pouches
• flexible containers
• glass containers

Question 24

what is over-pressure processing used for?

Answer 24

1. to protect package integrity (prevents pressure build up in packages at the beginning of cooling)
2. promotes better heat transfer during heating (better contact between package and contents)

Question 25

what determines the degree of over pressure?

Answer 25

proportion of steam and air

Question 26

in over pressure processing, higher steam content provides _____

Answer 26

better heat transfer

Question 27

in over pressure processing, higher air content provides ____

Answer 27

better overpressure protection

Question 28

what kind of turbulent conditions are used in over-pressure processing to achieve better heat transfer?

Answer 28

1. continuous venting (positive flow retorts) | 2. turbo fans (through mixing)

Question 29

how does overpressure processing change the pressure profile of a process?

Answer 29

pressure profile with NO overpressure has higher pressure than the retort during cooling. Thus, this creates a danger zone pressure profile WITH air overpressure has lower pressure than the retort during cooling. Thus, the whole process is in the safe zone

Question 30

what happens when there is no over-pressure to compensate for the high pressure inside a pouch compared to if overpressure is present?

Answer 30

if no overpressure: pouch will expand from the inside if overpressure is present: expansion will be supressed

Question 31

what are advantages of HTST?

Answer 31

- high quality - easy opening and disposal - easy reheating - easy storage

Question 32

what are disadvantages to HTST?

Answer 32

- slow speed (sealing limitation) - incomplete air removal - package failure (fragility) - more manual labor - needs overpressure processing

Question 33

why is rotational/agitation processing is used to optimize food processing?

Answer 33

to improve heat transfer by improving mixing and heat transfer coefficient

Question 34

what are the type types of rotation and agitation processing?

Answer 34

1. end over end 2. axial agitation 3. reciprocation agitation

Question 35

what kind of operation is axial rotation used for?

Answer 35

continuous operation

Question 36

what kind of operation is end over end rotation used for?

Answer 36

batch operation

Question 37

what are advantages of rotation/agitation processing?

Answer 37

- results in mixing of content - rapid heat transfer - uniform temperature - less overcooking of product - better quality retention - shorter process time/quicker turnover

Question 38

what type of container is end over end good for?

Answer 38

cans, semi rigid containers, glass containers

Question 39

what type of container is axial rotation good for?

Answer 39

only for cans

Question 40

what type of container is reciprocation agitation good for?

Answer 40

all types

Question 41

what are factors that influence rotary sterilization?

Answer 41

- product viscosity - can size - type of product - agitation speed - retort temp - head space - ratio of liquid to particles

Question 42

what is aseptic processing applied to?

Answer 42

liquid and acidic foods

Question 43

what is the main concept behind aseptic processing?

Answer 43

heat, hold and cool concept

Question 44

what are advantages to aseptic processing?

Answer 44

- high speed - continuous process - less damage to product - shorter processing time - uniform and high quality - reduced energy consumption

Question 45

what needs to be sterilized for aseptic processing?

Answer 45

- equipment - container - product (HTST) - environment

Question 46

what are disadvantages of aseptic processing?

Answer 46

- high initial capital investment - complexity of system - sophisticated instrument - need highly qualified personnel - can't be used for solid food or conductive products - process is not long enough to inactivate enzymes

Question 47

what is SSHE?

Answer 47

security, safey, health, environment management

Question 48

what is laminar and turbulent flow?

Answer 48

laminar: slow turbulent: high speed

Question 49

which fluid viscosity gives better flow for particulates: lower or higher viscosity?

Answer 49

- low density moves along top surface and has resistance with the bottom - high density moves along the bottom and has resistance with the top - fluid with equal density with liquid moves down the middle and moves fastest