Meat Science

CURING

• Curing may be defined as the addition of salt (Sodium chloride), sugar and nitrate or nitrite to the meat, which results in conversion of the meat pigments into the characteristic cured meat pigments imparting the characteristic cured meat colour and production of characteristic meat flavour.
• The process of meat curing is currently valued as a means of  imparting organoleptic qualities to the cured products,  though it originally was introduced as a means of preserving meat.
• Due to the advent of efficient and widespread refrigeration the need for preserving meat by curing alone has reduced.
• Apart from chacteristic colour and flavour, the meat packing industry is concerned with the following attributes also:  
  • Preservation,
  • Tenderness and
  • Yield.

Curing Ingredients

• Sodium chloride
• Sodium or potassium nitrate
• Sodium nitrite 
• Monosodium glutamate
• Sugar
• Acetic acid
• Vinegar and
• Spices

Action of Curing Ingredients

• Salt
  • Salt acts by dehydration and alteration of osmotic pressure so that it inhibits bacterial growth and subsequent spoilage.
  • It ionizes to yield the chlorine, which is harmful to the organisms.
  • It sensitizes the cells against CO₂.
  • It interferes with the proteolytic enzyme action.
  • The effectiveness of sodium chloride varies directly with its concentration and storage temperature.
  • An acceptable level of salts in hams has been reported to be about 3% and about 2% for bacon.
• Sugar
  • Sugar softens the products by counteracting the harsh and hardening effects of salt.
  • It interacts with amino groups of the proteins and upon cooking, forms browning of the products, which enhances the flavour of the cured meats.
  • Sugar substitutes have been used in bacon cures to prevent excessive browning during cooking.
  • It acts as a preservative by dehydration.
• Nitrates and Nitrites
  • Nitrates and nitrites bring about the desired pink colour development – nitrosyl hemochromes.
  • Both nitrates and nitrites are used where nitrates act as a reservoir for nitrites.
  • Nitrate raise the oxidation-reduction potential and therefore are more favourable to aerobic than anaerobic organisms.
  • They inhibit the growth of food poisoning and spoilage organisms. It has been clearly demonstrated that nitrite is effective in preventing the growth of the Clostridium botulinum organism.
  • They retard the development of rancidity.
  • Nitrate or nitrite alone or in combination of both shall not be more than 200 ppm in finished products as it is toxic.

• The European Directive 95/2/CE (1995) allows 150 ppm of nitrite (if alone) or 300 ppm when combined (nitrite plus Nitrate), and the residual values should be less than 50 ppm (if alone) or 250 ppm (if combined).
• There are more stringent limits for curing agents in bacon to reduce the formation of nitrosamines. For this reason, Nitrate is no longer permitted in any bacon (pumped and/or massaged, dry cured, or immersion cured).

Levels in finished products according to U.K. Regulations

• Nitrite as sodium nitrite (NO₂ as Na₂ NO₂) : Not to exceed 150 PPM in non heat treated products, while if sterilised only 100 PPM is allowed. The only exceptions are in traditional products.
• Nitrosamine
  • The reaction of nitrous acid (which is formed by the breakdown of nitrite) with secondary amides produces nitrosamine.
  • The reaction of nitrous acid with dimethyl amine is shown below:  
  • It is demonstrated that nitrosamine are carcinogenic compounds.
  • They have been isolated from cured meats in a few instances.
  • Work is now underway to determine the factor that controls their formation, but the final answer is not available.
• Phosphates
  • Alkaline phosphates are used to increase the water binding capacity and thereby the yield of the finished product.
  • Decrease the amount of shrinkage in smoked products when cooked.
  • To reduce the degree of purge or cook-pout in canned product so that the consumer receives a higher percentage of usable products.
  • Approved phosphates are
    • Sodium tripolyphosphate
    • Sodium hexa metaphosphate
    • Sodium acid pyrophosphate
    • Disodium phosphate
    • Only sodium acid pyrophosphate is permitted in sausages.
    • Legal limits for added residual phosphates are set at 0.5% in the finished products.
• Ascorbic Acid/ Ascorbates
  • Ascorbates take part in the reduction of metmyoglobin to myoglobin, thereby accelerating the rate of curing.
  • Ascorbates react with nitrites to increase the yield of nitric oxide from nitrous acid.
  • Excess ascorbate acts as antioxidant, thereby stabilising both colour and flavour.
  • The antioxidant properties of ascorbate not only prevent development of rancidity but also prevent fading of colour of sliced meats upon exposure to light.

Federation Regulations permits

• 0.75 oz ascorbic acid or 0.875 oz sodium bicarbonate per 100 pounds of sausage emulsion and
• 75 oz ascorbic acid or 87.5 oz sodium bicarbonate per 100-gallons pickle for curing primal cuts.
• Monosodium glutamate (MSG)
  • It has been used in a number of products to enhance the flavour.
  • There is little advantage of its use in cured meat products. It is added at 0.1% level.  

Abstract of ingredients used, their level of addition and function

Sl. No.	Name of Ingredient	Level in brine solution	Function (Action)
1.	Sodium chloride	15 to 30%	Preservative, improves texture
2.	Sodium nitrate	0.15 to 1.5%	A source of nitrate
3.	Sodium nitrite	500 to 1000 ppm	Preservative, reduced by meat enzymes to nitrous oxide, which combined with myoglobin to form nitrosomyoglobin, the cured red pigment
4.	Polyphosphates	2 to 4%	Reduce cooking loss, e.g. during smoking; improve texture
5.	Sugar (Sucrose, maple syrup)	1to 4%	Improves flavour by masking the harshness of the salt
6.	Liquid smoke	Ca. 1%	Flavouring agent
7.	Sodium ascorbate	0.2 to 1%	Reducing agent. Improves colour formation and stability by effecting rapid reduction of NO3 to NO2 in the meat.