Meat Preservation techniques

By

Dr. Geeta ChauhanSenior Scientist

Division of Livestock Products Technology

Indian Veterinary Research InstituteIzatnagar, Bareilly (UP), India

Introduction

Food preservation has been known and used since ancient times. The art was used to preserve various food commodities like meat, fish, fruits and vegetables, by applying methods such as drying, salting and smoking etc. These traditional methods are of great importance in present times as well. With the advancements, the food preservation has become more a science based on the latest developments in science and technology.

Principle

The primary cause of food spoilage is the action of micro organisms like bacteria, molds or yeasts added by enzymes. These microbes require favorable environment for their survival and under unfavorable conditions, they fail to grow and die. The prevention of food spoilage is the primary purpose of food preservation. Thus, the underlying principle of food preservation methods is to create the unfavorable conditions for the spoilage micro organisms.

Factors affecting microbial growth

Intrinsic Factors Extrinsic Factors

Moisture content Water activity pH Redox potential Physical structure

of the food Available

nutrients

Temperature Relative humidity Carbon dioxide or

Oxygen Types and number

of micro organisms in the food

Principles of Meat Preservation

1.Cold Treatment- it further includes

I.Refrigeration- •By efficient refrigeration, meat can be preserved in a condition approaching its natural state for periods adequate for commercial requirements.•The appearance, weight and flavor of meat are little affected.•In refrigeration, meat temperature decreases to 4-7ºC or even to 1-2ºC in meat intended for longer storage.

• Techniques used for carcass refrigeration may be categorized as

Dry (air) refrigeration- this technique used in meat industry is of three types-1.Slow air refrigeration-•It is mainly used in small abattoirs•Involves 3 stepsStep 1- carcass ‘draining’ or ‘drying’Step 2- Pre refrigeration- at 10ºC; 75% RH

Dry (air) refrigeration

Used for red meat and poultry carcasses

Wet (water) refrigeration

Used for poultry

Step 3- Refrigeration- at 4-7ºC; 85- 90% RH• In this method, dry carcass surface is beneficial in terms of surface micro flora suppression and causes weight loss of 3%.

2. Rapid air refrigeration-• carcasses are exposed to air at -1 to +1ºC, 90% RH and 1-3m/sec circulation for 18-36 hrs.• It causes weight loss of 1.5-2%

3. Ultra rapid refrigeration- involves two phases Phase I- carcass exposed to intensive circulation (2-4m/sec) at temp. -4 to -6ºC; 90% RH for 1-3 hours. Phase II- carcass is refrigerated at -1 to 2ºC for 14-22 hours with circulation 0.3 m/sec.• Weight loss is around 1%.

Wet (water) refrigeration- this method can be applied by

1.Spraying poultry carcasses with cold water- it is a hygienic practice as reduces chances of cross contamination. this method requires considerable amount of water ( 10-12 lit/ carcass).

1.Submerging the carcasses in basins with running cold water, for 1 hour- this method requires lesser amount of water (up to 4 lit/ carcass).

II. Freezing-• In Industrial abattoirs, freezing of meat

is done in ‘freezing tunnels’ under air circulation of 2-4m/sec with air at -20 to -40ºC and 95- 100% RH.

• The cryoscopy points of meat is between -1.5 and -1.8ºC (muscle tissue) and -2.2ºC (fatty tissue).

• Approximately 75% of water in meat is freezes at -5ºC, 90% at -30ºC and 100% at -60ºC.

• During frozen storage, microbial storage is inhibited.

• Frozen meat products can be stored for longer duration up to 12 months.

• Disadvantage- Freezing may cause some adverse effects on meat quality that may affect its sensory characteristics.

2. Salting and Curing-• Salting- treatment of meat with salt Curing- treatment of meat with brine i.e., mixture of salt, nitrites/ nitrates and other compounds.• It can be done by application of either of the 3 methods-a.Dry method- meat surface is treated with dry salt or brine and held at temperature 0-7ºC for 2-4 weeks. During this period, salt or brine ingredients goes into the meat and thus, releases amount of bound water.b.Wet method- meat is submerged in salt/ brine solution. This allows ingredients to diffuse from solution into meat.c.Combined method- meat is firstly dry salted or cured and then, heated with salt/brine solution.•Various ingredients used for salting and curing are- Sodium chloride, Sodium nitrite, Sodium ascorbate, Sugars.

3. Smoking- • Two main objectives of applying smoking technique are- to achieve popular color and flavor to inhibit spoilage and pathogenic micro organisms.• Smoke is produced endothermically from damp wood chips.

Smoking

Traditional Plants meats are hung in room having wood containers for smoke production conditions are difficult to handle.

Modern Plants smoke is produced by industrial generators conditions are well controlled having temperature of 200ºC.

4. Drying-

• It involves migration of moisture from inner layers towards surfaces and evaporation from the surface.• Initially, drying is done at low temperature of about 10-15ºC and as water activity decreases, temperature is increased that enhances drying rate.• Drying should be done in a gradual manner to avoid the formation of hard, dry layer on surface.• Lyophilization- method of meat drying Here, meat is frozen and then exposed to very low pressure in vacuum at 20-40ºC. This results in the removal of 90% of water and meat product of same volume but 70% of initial weight.

5. Heat treatment-• Involves- killing of pathogenic microbes inactivation of meat enzymes• The heat treatment may be done in following ways-a.Pasteurization- in water at temperature < 100ºCThis destroys all vegetative cells of psychrophilic and mesophilic microbes but vegetative cells of thermophilic bacteria and spores survive.b.Boiling- in water at 100ºC so as to reach product’s center temperature at 80-90ºCThis kills all vegetative cells but not the sporesc.Sterilization- at temperature > 100ºC in autoclaveThis kills all vegetative forms and spores

6. Fermentation-

• Fermentation is a phase of intensive growth and metabolism of lactic acid bacteria.• The activity of this bacteria produces lactic acid that reduces the pH and thus, acting as a preservative.• The process occurs normally over 2-5 days until pH lowers to 4.6-5.• To enhance the speed of fermentation, selected lactic acid bacteria called ‘artificial culture’ can be added.

Hurdle Concept and Technology

• Hurdle technology is a method of controlling or eliminating pathogens in food products by combination of approaches.• These approaches can be thought of as ‘hurdles’ the pathogen has to overcome to remain active.• The right combination of hurdles ensure elimination of all pathogens or reducing them to harmless in the final product.• In developing countries, the application of hurdle technology is very important for foods that remain stable, safe and tasty without refrigeration storage.• Some of the principle hurdle used in food preservation are-

Parameter Symbol ApplicationHigh Temperature F Heating

Low Temperature T Chilling, Freezing

Reduced water activity

aw Drying, curing, conserving

Increased acidity pH Acid addition or formation

Reduced Redox potential

Eh Removal of oxygen or addition of ascorbate

Biopreservatives Competitive flora such as microbial fermentation

Other preservatives

Sorbate, sulfites, nitrites.

• Some hurdles may influence the safety and quality of foods because of anti microbial properties and at the same time, improve the flavor e.g.. as in Maillard reaction.• The same hurdle could have positive or negative effects on foods depending upon- microbial stability its intensity

Basis of hurdle technology

• The physiological responses of microbes i.e., their homeostasis, metabolic exhaustion and stress reaction forms the basis of application of Hurdle technology.• The disturbance of the homeostasis is the key phenomenon of food preservation.

• The goal for food preservation is the multi target preservation of foods in which logically applied hurdles will have a synergistic effect.• Thus, hurdle technology is an important tool to enhance shelf life of livestock products.• It can also be used for the development of various novel food products.

Thank you….