Cooking and smoke application
usually are part of the same process
because they are cooperative and
occur under similar conditions --controlled heat and humidity
Objectives of cooking
1. pasteurization/sterilization
– “beware the load”
– more contamination will require higher temperature and/or
longer time --- because inactivation rate is constant
log no.
of
organisms
Time at x degrees
2. develop/retain quality flavor, juiciness, texture,
aroma, appearance, etc.
3. may include fermentation/incubation before final
Some specific requirements for controlling
Listeria monocytogenes…
– If, after cooking, ready-to-eat (RTE) products are
“exposed to the environment” after the lethality
(kill) treatment (i.e., not cooked in the package,
etc.), then processors must (9 CFR Part 430) meet
one of three alternatives:
– Alternative 1- A post-lethality treatment
-i.e., treatment (after packaging, etc.) that is
validated to reduce or eliminate L. monocytogenes
(reheating, HPP, etc.) AND a antimicrobial agent
to limit growth of survivors
– Alternative 2 – A post-lethality treatment OR a
antimicrobial agent AND verified sanitation and
testing program that shows control of L.
monocytogenes
– Alternative 3 – A verified sanitation and testing
program
“Stabilization” of Cooked Meat and Poultry
(Appendix B)
– For control of spores (Clostridium perfringens) in
heated, RTE products
-maximum internal temperature must not remain
between 130°F and 80°F for no more than 90
minutes, and between 80°F and 40°F for no more
than 5 hours.
-for products with 100 ppm or more ingoing
nitrite, the 130°F- 80°F window is 5 hours and
80°F - 45°F window is 10 hours
Objectives of smoke application
1. flavor
2. color
3. preservation
– antimicrobial
– antioxidant
4. surface protein coagulation
– “skin” for skinless products without casings
– control of “snap” on first bite
Cooking (thermal processing) considerations
1. heating medium
– hot air
– electrically heated
– gas heated
– steam
– hot water
– cooking tanks
– microwave
– limited to few applications such as precooked bacon
2. heat and mass transfer
– heat is transferred to product surface (convection)
hot air
then ----
into the product (conduction)
at the same time, moisture is migrating to the surface and
evaporating from the surface
H20
This is mass transfer
(weight loss)
–is very important
because the
evaporation cools the
product
Therefore, the air-product temperature differential is
important to drive heat transfer but the relative humidity
is also critical because it affects cooling of the product
surface
To control the cooking process:
1. must know and control dry bulb temperature
– thermocouple suspended in air
2. measure and control wet bulb temperature
– thermocouple covered with a water-saturated
fabric sack
– cooling rate indicates air humidity
Tables for conversion:
Examples:
dry bulb
160oF
160oF
160oF
wet bulb
156oF
152oF
147oF
R.H.
90%
80%
70%
160oF
142oF
60%
This is also critical to smoke application color
development, emulsion/batter stability and casing
peelability
3. air velocity
– air flow increases heat energy contact but also
increases evaporation
4. time control
– for holding temperature/humidity combinations in
stepwise sequence
Example: 460 frankfurters
15 minutes
30 minutes
10 minutes
---
D.B.
129
158
176
176
W.B.
104
140 (smoke)
165
176 to 160oF internal
–cooking steps are most often controlled by time but may also
be controlled by temperature
– T processing is the concept of keeping the internal product
temperature and the heating air temperature at a constant
differential
Example:
T = 30oF
Temp.
30oF
air
30oF
T processing is believed
to allow the best protein
gelation if the “ideal T”
for each product can be determined
Time
“Stepdown” cooking processes
– start at high temperature and decrease dry bulb as product
internal temperature increases
– often used for products like roast beef --- to retain internal
rare/medium rare appearance
air
Temp.
Time
Effects of cooking on product
1. at the beginning:
– warm air, cold product = surface condensation
– surface temperature is essentially wet bulb temperature
– cooking rate determined by wet bulb temperature
– excessive condensation is a potential problem for
emulsion/batter products because fat heats faster than
water --- a quick temperature increase of a “wet”
product may overheat the fat and break the emulsion
membranes resulting in fat separation and pooling
– first cook step is usually with relatively low heat and drying
to remove excess surface condensation and begin raising
surface temperature
– second step is usually smoke application - with increased
heat and humidity
– because smoke deposition is much better on a moist (but no
condensation) surface
Processing Hint:
For more smoke deposition, start smoking sooner
rather than trying to smoke longer
2. finishing
– after the surface dries, surface temperature will
exceed wet bulb
– product internal heating rate increases and dry bulb
temperature becomes more important as the driving
force
– dry surface accelerates cooking but excessive drying will
result in a hard surface
Smoke application
– natural smoke is not a “flavoring agent” for
labeling
natural wood smoke composition:
– particulates
– 90% of volume ash, tar, mostly undesirable
– gaseous (vapors)
– responsible for desirable properties of smoke
– very complex
– ~ 400 chemical compounds
Gaseous/vapor composition
of wood smoke
1. alcohols ~ 15
– methanol = “wood alcohol”
– antimicrobial compounds
2. organic acids ~ 12
– formic, acetic, propionic
– antimicrobial
– very important to surface “skin” on products
3. phenols ~ 25
–
–
–
–
may be the singly most important group of compounds
antimicrobial
flavor and aroma
strong antioxidants
– some color contribution
– sometimes used as a measure of smoke deposition by (phenol content chemical analysis)
4. carbonyls ~ 50
– color development by reaction of carbonyls with protein
– facilitated by a dry surface
– better browning at 6 - 10% surface moisture
– also may contribute some flavor
5. polycyclic hydrocarbons ~ 30
– problem in natural smoke
– carcinogenic/mutagenic
– most common are
benzopyrene
dibenzanthracene
– some countries regulate amount on products
– Germany - 1 ppb in smoked meats
Composition of wood smoke can be controlled by
generation (burning/smoldering) temperature
– general range --- 300oF - 750oF
acids are favored at
400oF - 500oF
phenols
600oF
polycyclic hydrocarbons
750oF+
glowing sawdust indicates temperatures of 800 - 900oF
– most recommendations are ~ 600 - 650oF for best
composition
Smoke “quality” depends on
1. generation temperature
2. oxidation reactions --- amount of air introduced
by fans during smoke formation
3. wood source
– hickory commonly preferred but there are
many options --- apple, mesquite, alder
– most often sawdust is a hickory and
hardwoods mixture
4. air temperature --- increase vapor phase
Maximizing smoke deposition
1. smoke density
– dependent on generator
– temperature, moisture content of sawdust
2. air flow velocity
– circulating air forces smoke/product contact
but also decreases smoke density
– compromise
3. air temperature
– increased temperature increases vaporous phase of
smoke but is limited by product surface --- probably
drying at high temperature
4. product surface moisture
– may be single most important factor
– certainly very frequent source of problems
– greater moistness increases deposition but
condensation gives streaks and/or blotches
80% R.H.
condensation
on surface
– also increase color intensity with moisture and can
become too dark
–steam smoking = black colors
5. surface permeability
– casings
6. multiple stage applications
– 5 minutes on, 5 minutes off, 5 minutes on may
give better deposition than 10 minutes on
– may allow better penetration if the surface
becomes saturated each time
7. electrostatic smoking
– smoke particles carry electrical charge so placing
a charge on the product will increase attraction
Typical cook/smoke sequence
for meat products
1. conditioning/equilibration
– 15 minutes at 110oF/100oF
– allow surfaces to reach uniform temperature
2. drying
– 10 minutes at 150oF/100oF
– remove excess condensation
3. smoke application
– 30 minutes at 160oF/100oF --- or less
– wet bulb needs to be equal to or less than the previous step to
prevent condensation
– surface must be moist
4. color development
– 15 minutes at 180oF/120oF
– raise internal to 130-140oF for cured color
– maximize external color reaction of carbonyls from
smoke with meat proteins
5. cook
– at 180oF/160oF or 180oF/180oF to reach 160oF
internal
– increase humidity to minimize weight loss (mass transfer)
6. finish/chill
– 10 minutes shower with cold water
– accelerate chilling
– may brine chill, blast chill to minimize weight loss
during cooling
– meet Appendix B requirements
Liquid smoke (now called “Condensed smoke”)
– available as water-based or oil-based preparations
– collected from natural smoke therefore includes
essential components (phenols, carbonyls, acids)
for important smoke properties
but
without polycyclic hydrocarbons
Advantages of liquid smoke
1. uniformity/consistency
2. simple, sanitary, cleaner
– smokehouse cleaning from traditional smoke is a
dirty, dangerous, expensive operation
3. decreased air emissions
4. removal of carcinogens
5. cost
estimates ~ 50% of natural
(if cleaning costs are included)
However - cannot be labeled “naturally smoked”
Liquid smoke application
1. atomization/regeneration
– atomization - use of air pressure to vaporize liquid
smoke
– regeneration-heating liquid smoke to regenerate
vapors
– applied similar to natural smoke in batch-type
chambers
– product drying/surface moisture requirements are
similar to that for natural smoke
2. drenching
– showering product surfaces with liquid smoke
– most popular application method for frankfurters in
U.S. (70-80%)
– fast process, saves time in overall cook/smoke
sequence
– runoff is reused, little waste
3. direct addition
– addition to mixer/chopper or injected with brine
– provides uniform, consistent flavor but lacks surface
color
– be careful of acidity - special formulations of smoke
are available for direct addition
– label as “smoke flavoring added”
4. smoked casings/nets
– pre-smoked casings or nets allow absorption from
casing after stuffing
– achieves surface color move similar to natural smoke
(may not be exactly the same)
– must consider humidity during the early cooking
stages to develop and set the color --- again similar to
natural smoke application