Meat Science

INTERMEDIATE MOISTURE MEAT PRODUCTS

• Sundrying of meat was one of the earliest preservative techniques used by man.
• Such meat had meager dehydration capacity resulting in poor juiciness and texture.
• Later studies revealed that meat products with 20-50% moisture had moderate juiciness and texture on rehydration.
• Such products were resistant to bacteriological spoilage and could be held without refrigeration.
• These products were referred as Intermediate Moisture Meats (IMM).
• The basic reason for the stability of these products lay in the reduced availability of water to the microorganisms.
• Since water activity generally remains in the range of 0.6 to 0.85.
• These semi-moist meats are of special significance to the developing countries where refrigeration facilities are not always available.
• Such products can be easily carried in defense expeditions and stress situations like floods, famines, for airdrop, etc.

Humectants

• Various additives employed for lowering the water activity of foods are known as humectants.
• Some of the most commonly used humectants are:
  • Glycerol
  • Propylene glycol
  • Sodium chloride
  • Polyhydric alcohols (e.g. sorbitol)
  • Sugars (e.g. sucrose, dextrose, corn syrup etc)
• The humectants are generally low molecular weight compounds, which are easily soluble in water.
• These are chemically inert and do not modify the normal sensory qualities of the product.
• Besides, these compounds are edible in large quantities without any adverse effect.
• In addition to humectants, use of antimycotic agents like potassium sorbate, sodium benzoate, propylene glycol etc. is a must in the semi-moist meats because 0.6 to 0.85 water activity ranges specifically permits the growth of moulds.

Basic processing techniques

Moist infusion or desorption

• It involves soaking and / or cooking of meat chunks or cubes to yield a final product having desired water activity level,
• E.g. sweet and sour pork, Hungarian goulash etc.

Dry infusion or adsorption

• It involves initial dehydration of meat chunks or cubes followed by soaking in an infusion solution containing desired osmotic agents.
• E.g. ready-to-eat cubes of roast pork, chicken a la king, etc.

Component blending

• In this process dry and wet ingredients or components are blended, cooked and extruded or otherwise mixed to give a final product of desired water activity.

Whatever process is adopted, the thumb rules for the preparation of IMM are:

• Reduction of water activity by addition of humectants,
• Retardation of microbial growth by addition of antimicrobial especially antimycotic agents and
• Improvement of sensory properties such as flavour and texture through physical and chemical treatments.
• Composition of infusion solution developed by Brockmann (1970) for the preparation of sweet and sour pork (a_w=0.85) is given below to give an idea about the balancing of various additives:

Ingredients	Percentage
Glycerol	25.0
Catsup	23.55
Water	15.00
Vinegar	13.50
Sucrose	11.84
Starch hydrolysate	14.50
Salt	2.59
Corn starch	2.30
Monosodium glutamate	1.15
Potassium sorbate	0.30
Mustard powder	0.24
Onion powder	0.02
Garlic powder	0.01

 

 

Stability of intermediate moisture meats

• IMF products are fairly stable at ambient temperature for several weeks or even months.
• However, prolonged storage may result in some quality deterioration due to the following reasons:
• Limited breakdown of both myofibrillar and sarcoplasmic proteins.
• Collagen being more susceptible to degeneration results in more hydroxyproline formation.
• Degradation of haemoprotein (myoglobin and haemoglobin) causing loss of colour
• Development of rancidity
• Non-enzymatic browning resulting in loss of colour, consumer appeal, nutritive value and possibly off-flavour
• Formation of lipid protein crosslinks causing decreased water binding capacity and net protein utilisation of meat products.