3. Curing agentsNitrite (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”!

– 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)

Nitrite

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

reductants

myoglobin-Fe++ myoglobin-Fe+++

| |

NO NO

4. proteins

– sulfhydryl amino acids

SH

SH

S

S+ NO2

- + 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 nitritea. 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 ingredients4. 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