Transcript 3. Curing agents Nitrite (sodium or potassium)….. and nitrate

3. Curing agents
Nitrite (sodium or potassium)…..
and sometimes nitrate
– functions only by conversion to nitrite first
– useful only in dried products such as dry sausage or
country cured/prosciutto hams
– 7 lbs per 100 gal of pickle;
3 1/2 oz per 100 lbs meat for dry cure;
2 3/4 oz per 100 lbs of meat when used for chopped
– when nitrate is used, microbial conversion to nitrite is required
– Micrococcus sp. (now Kocuria sp.) have catalase to convert
NO3- to NO2– sometimes included in starter cultures as a cured color
promoting agent
–now often part of “naturally cured” products labeled “Uncured”!
Nitrite
– definitely magic - distinctive, absolutely no
substitute
– permitted at 2 lbs per 100 gal of pickle (10% pump);
1 oz. per 100 lbs of meat for dry cure;
1/4 oz per 100 lbs of chopped meat.
Cannot exceed 200 ppm in finished product
– except bacon  120 ppm nitrite plus maximum (550
ppm) ascorbate or erythorbate
– defines a “cured” product --- almost always includes salt as
well when “cured”
– not permitted in baby foods (sterilized)
Functions of nitrites (NO2-) in curing
1. color
– due to nitric oxide (NO) from nitrite NO2– promoted by acid conditions
– accelerated by reductants, pigments (Fe) and salt
2. microbial inhibition
– very effective against Clostridium botulinum but is
inhibitory toward many organisms both pathogens
and spoilage organisms
3. antioxidant
– very effective for preventing rancidity particularly preblends
4. flavor
– likely produces a unique “cured” flavor but this has
never been chemically identified
5. texture
– nitrite reacts with sulfur-containing amino acids to
form crossbridges between proteins
So:
an absolutely critical step in meat curing is
forming nitric oxide (NO) from nitrite (NO2-)
Conditions which increase nitric oxide formation
1. pH
2NO2- + 2H+  2HONO  NO + NO3- + 2H+
nitrous acid
nitric oxide
nitrate
– decreases pH by 0.2 - 0.3 pH will double the production
rate of NO
– may add sodium acid pyrophosphate or glucono delta
lactone to decrease product pH
2. reductants
sodium ascorbate or erythorbate, ascorbic acid or
erythorbic acid
– react directly with nitrite to produce nitric oxide
3. meat pigments
myoglobin-Fe++ + NO2-  myoglobin-Fe+++ + NO
myoglobin-Fe++
|
NO
reductants

myoglobin-Fe+++
|
NO
4. proteins
– sulfhydryl amino acids
SH
SH
+ NO2
-
S
S
+ NO
5. salt
NaCl + NO2-  NOCl-  NO + Cl-
Nitrite is very reactive and reacts with many
things in a meat system
– most are positive reactions
--- but --nitrite can also react with secondary amines
NH + NO2  N – NO
nitrosamine
– a definite carcinogen at
ppb concentrations
–formerly a problem in
bacon
Nitrosamines are controlled by:
– low residual nitrite when bacon is fried
– presence of reductants to encourage other
nitrite reactions
Related problem with rubber nettings used to
hold hams for smoking
– butyl-amine in rubber reacted with nitrite in
hams to produce butylnitrosamine
Concerns for nitrite
a. toxicity
– very reactive, toxic
– lethal dose is about 1 g (14 mg/kg body weight)
– relaxes smooth muscle and reduces blood pressure
– methemoglobinemia
– human exposure to nitrite/nitrate is about 80% -vegetables,
10-15% - water, ~ 5% or less - cured meat
– ingested nitrate is absorbed and secreted in saliva
( ~ 25% of that is absorbed) and about 20% of that is
converted to nitrite by oral - cavity microorganisms
– must maintain records of use for USDA when making
products
– most processors use “Modern Cure”, “Prague Powder”,
“Legg Cure” - brand names for curing mixture:
6.25% sodium nitrite
93.75% sodium chloride
pink dye
because:
pure nitrite is a white crystal very similar to
sodium chloride
– Germany and European Community countries do
not permit use of pure nitrite, only salt/nitrite
mixtures
b. nitrosamine formation
– controlled by controlling residual nitrite
Sidelight:
– nitric oxide has become an important topic
in human physiology
– involved with brain cell communications,
control of smooth muscle contraction and
immune system attacks on invading bacteria,
wound healing, etc.
Non-meat ingredients
4. Reductants
– sodium ascorbate or erythorbate,
– permitted up to 7/8 oz per 100 lbs (547 ppm);
87.5 oz per 100 gal pickle (10% pump)
ascorbic acid or erythorbic acid
– permitted at 3/4 oz per 100 lbs of meat;
75 oz per 100 gal of pickle (10% pump)
– ascorbate/erythorbate most common because acid
forms can be too reactive with nitrite
– ascorbic acid, ascorbate  Vitamin C
– erythorbic acid, erythorbate - optical isomer, not
biologically active
– ascorbate/erythorbate are equivalent in terms of meat
curing
Primary function is to increase nitrite curing reaction
NO2-  NO
but also helps to maintain cured color during
storage (reductant)
– 10% solution may be used to spray surface of cured
products prior to packaging - treatment cannot result in
significant added water
– very effective for improving stability of fresh
meat color but not permitted --- too effective!
Reductants
– for brines/injection curing
– should be dissolved immediately after the
phosphates --- otherwise may remain
undissolved and result in weak or uneven
curing reactions
– brines for injection should be made up:
1. phosphates
2. ascorbate/erythorbate
3. salt, sugar, etc.
4. nitrites
Non-Meat Ingredients
5. Acidulants
– acid compounds to reduce pH and accelerate
nitric oxide (NO) production --- trade-off
with WHC
– objective is 0.2-0.3 pH change
– also permitted as spray to improve peeling of
frankfurters (5% citric acid or 35-40 grain
vinegar)
For cure acceleration:
1. sodium acid pyrophosphate (SAPP)
– acid phosphate
– permitted at 0.5%
2. glucono delta lactone (GDL)
– permitted at 0.5% as a cure accelerator
– may also be used at up to 1% in dry sausage to
simulate fermentation
Acidulants may also be added in encapsulated
form for slow release to simulate fermentation
– lactic acid or citric acid