Principle of meat preservation
By Lourdes Santos-Rivera
Meat preservation is principally concerned with application of measures to delay meat spoilage, which is caused by microbial, chemical and physical changes. Microbial spoilage (caused by bacteria) is most common. Microbes thrive in moisture and since meat is 70 to 75 % water, it spoils easily through microbial action. Meat, being a rich source of nutrients, also becomes an excellent food for bacteria.
Methods of meat preservation, however different from each other, are alike in the way they employ environmental conditions that discourage the growth of microorganisms. They may be grouped in three broad categories based on :
a)control of temperature
b)control of moisture
c) lethal agents (bactericidal, bacteriostatic, fungicidal and fungistic.)
Generally, the method of discourage microbial growth can be divided into groups:
-by exposing meat to high (100 degrees Celsius) or low (0 degrees Celsius) temperature.
-by treating meat with substances (e.g. salt, nitrate, and other chemical preservatives) which will kill microorganisms or delay microbial actions.
-Microbial growth
-atmospheric oxidation
-enzymatic reaction
Microbial growth
Meat contains abundant nutrients required for the growth of bacteria, yeast and molds (microorganisms which cause food spoilage). Thus, these microorganisms flourish in meat. Eliminating the growth requirements:
-temperature requirements
-moisture content
-nutrient content
-oxygen (for aerobic microorganisms)
Are the most important considerations in the control of their growth. This can be achieved by removing one, two or all the required conditions for growth.
Atmospheric Oxidation
Meat fats are susceptible to oxidation, when they are exposed to the molecular oxygen present air. This results in the production of a strong rancid color and flavor in the cooked product. When this chemical reaction occurs, it constitutes a defect referred to as oxidative rancidity. More popularly known as rancidity or manta, this can be avoided by eliminating the factors required for its development. These factors are light, air and free fatty acids. While the entry of light and air can be prevented ,free fatty acids esily form from the meat fats. Antioxidants are compounds which react with certain intermediary products necessary for the development of free fatty acids.
Enzymatic reaction
This is another common cause of food spoilage. Enzymes are protein substances which will help speed up chemical reactions. Enzymatic reaction may be reduced or totally stopped if you subject the meat to temperature below or above the temperature range needed for the activity of the meat enzymes.
Drying– removal of moisture from meat of moisture from meat. The method involves the reduction of the original water content (70% of the meat to about 15%).
There are two ways of drying:
Natural sun drying- natural sunlight is used to reduce the moisture content of meat.
Artificial drying- a chamber equipped with heating elements maintained at a temperature, of 110-120 Fahrenheit and relative humidity of 85% is used for drying . This is more expensive than sun drying but its dried products have better quality and can be sold at a higher price.
Smoking – there are two methods of smoking:
-Natural– is the exposure of the meat to wood smoke which causes the deposition of pyroligenous acid on the meat surface that acts as preservative and flavoring agent. Hard-wood, saw dust, guava leaves or any kind of wood may be used.
–Artificial – smoke flavor is incorporated in the pumping pickle for ham and bacon at the rate of 1 teaspoon (tsp.) /liter.
Salting– simple method or dehydration in which salt causes the withdrawal of water from the tissue of both the meat and the spoilage organisms, resulting to the shriveling and inactivation of the cells.
Source:
Meat Specialties of the Philippines
MARID agribusiness January 2005